HomeMy WebLinkAboutOCSD 19-17RESOLUTION NO. OCSD 19-17
A RESOLUTION OF THE BOARD OF DIRECTORS OF THE
ORANGE COUNTY SANITATION DISTRICT APPROVING AND
ADOPTING THE 2019 ORANGE COUNTY REGIONAL WATER AND
WASTEWATER HAZARD MITIGATION PLAN
WHEREAS, the United States Congress passed the Disaster Mitigation Act of
2000 emphasizing the need for pre-disaster mitigation of potential hazards; and
WHEREAS, the Disaster Mitigation Act of 2000 requires all cities, counties and
special districts to develop and adopt a Hazard Mitigation Plan (HMP) to be eligible to
receive federal grants pertaining to disaster preparedness; and
WHEREAS, the Orange County Sanitation District ("OCSD") recognizes that the
threat from natural hazards poses a risk to water and wastewater utilities and the
individuals they serve, and impacts can result in regional economic and public health
consequences; and
WHEREAS, by planning for natural and manmade hazards and implementing
projects that mitigate risk, utilities can reduce costly damage and improve the reliability of
service following a disaster; and
WHEREAS, the Municipal Water District of Orange County, OCSD and 18 other
member agencies participated in development of the HMP in conjunction with a
consultant; and
WHEREAS, the resources and information within the HMP will allow OCSD and
the member agencies to identify and prioritize future mitigation projects, meet the
requirements of federal assistance programs and grant applications, and encourage
coordination and collaboration in meeting mitigation goals; and
WHEREAS, a Planning Team was formed to participate in the FEMA-prescribed
mitigation planning process to prepare the HMP; and
WHEREAS, a public outreach strategy was employed as a required component of
developing the HMP, including posting information on member agency websites, email
and social media distribution, community survey, and presentations at the Orange County
Business Council and Orange County Emergency Management Organization meetings;
and
WHEREAS, the HMP was made available for public review from August 10, 2018
to September 10, 2018, and
WHEREAS, on October 15, 2018 the HMP was provided to the California
Department of Emergency Services (CalOES) for review; and
OCSD 19-17-1
WHEREAS, the HMP was revised based on CalOES feedback and was submitted
to the Federal Emergency Management Agency (FEMA) for review on February 20, 2019;
and
WHEREAS, the HMP received FEMA Approval Pending Adoption on July 16, 2019
subject to the member agencies adopting resolutions approving and adopting the HMP;
and
WHEREAS, the Board of Directors have reviewed the HMP; and
WHEREAS, the HMP identifies and assesses hazards most likely to affect OCSD
and provides actions to mitigate them.
NOW, THEREFORE, the Board of Directors of the Orange County Sanitation
District, DOES HEREBY RESOLVE, DETERMINE, AND ORDER:
That the Orange County Regional Water and Wastewater Hazard Mitigation Plan
attached as Exhibit "A" is hereby approved and adopted by OCSD.
PASSED AND ADOPTED at a regular meeting of the Board of Directors held September
25, 2019.
APPROVED AS TO FORM:
OCSD 19-17-2
STATE OF CALIFORNIA
SS
COUNTY OF ORANGE
I, Kelly A. Lore, Clerk of the Board of Directors of the Orange County Sanitation
District, do hereby certify that the foregoing Resolution No. OCSD 19-17 was passed and
adopted at a regular meeting of said Board on the 25th day of September 2019, by the
following vote, to wit:
AYES:
NOES:
ABSTENTIONS:
ABSENT:
Avery, Beamish (Alternate); Bernstein; Berry (Alternate);
Chaffee; Collacott; Ferryman; Harper (Alternate); Iglesias;
Kim; Kring; Massa-Lavitt; R. Murphy; Nguyen; O'Neill
(Alternate); Shawver; Shea; Silva; F. Smith; Wanke; and
Withers
None
None
B. Jones (Alternate); M. Murphy; Parker; and Peterson
IN WITNESS WHEREOF, I have hereunto set my hand and affixed the official seal
of Orange County Sanitation District this 25th day of September 2019.
OCSD 19-17-3
FINAL
Orange County Regional Water
and Wastewater
Hazard Mitigation Plan
Prepared by:
MUNICIPAL WATER DISTRICT OF ORANGE COUNTY
18700 Ward Street
Fountain Valley, California 92708
Contact: Kelly Hubbard
WEROC Programs Manager
714.593.5010
MICHAEL BAKER INTERNATIONAL
5 Hutton Centre Drive, Suite 500
Santa Ana, California 92707
Contact: Ms. Kristen Bogue
949.855.5747
GPA CONSUL TING
2642 Michelle Drive, Suite 110
Tustin, California 92780
Contact: Ms. Starla Barker, AICP
310.792.2690
August 2019
JN 161720
This document is designed for double-sided printing to conserve natural resources.
TABlE OF CONTENTS
Section 1.0 lntroduction ................................................................................................................................... 1-1
1.1 Purpose of the Plan and Authority ....................................................................................... 1-3
1.2 Multi-Jurisdictional Participation ........................................................................................... 1-5
1.2. 1 Overview of Water and Wastewater Systems in Orange County .............................. 1-5
1.2.2 Participating Jurisdictions .......................................................................................... 1-6
1.3 What is New/What Has Changed from the 2012 Plan ......................................................... 1-8
1.4 Plan Organization ................................................................................................................ 1-9
Section 2.0 Planning Process Documentation .............................................................................................. 2-1
2. 1 Organizing Resources ......................................................................................................... 2-1
2. 1. 1 Project Management Team ....................................................................................... 2-2
2. 1.2 Planning Team .......................................................................................................... 2-2
2. 1.3 Public Outreach ........................................................................................................ 2-6
2. 1.4 Review and Incorporate Existing lnformation ............................................................ 2-8
2.2 Assess Risks ....................................................................................................................... 2-8
2.2. 1 Identify/Profile Hazards ............................................................................................. 2-9
2.2.2 Assess Vulnerabilities ............................................................................................... 2-9
2.3 Develop Mitigation Plans ..................................................................................................... 2-9
2.3. 1 Identify Goals ............................................................................................................ 2-9
2.3.2 Develop Capabilities Assessment ............................................................................. 2-9
2.3.3 Identify Mitigation Actions ....................................................................................... 2-10
2.3.4 Plan Review and Revision ...................................................................................... 2-10
2.3.5 Plan Adoption and Submittal ................................................................................... 2-10
2.3.6 Plan Maintenance ................................................................................................... 2-10
Section 3.0 Risk Assessment .......................................................................................................................... 3-1
3. 1 Hazard Identification and Prioritization ................................................................................ 3-1
3.1. 1 Hazard Identification ................................................................................................. 3-1
3. 1.2 Hazard Prioritization .................................................................................................. 3-4
3.2 Hazard Profiles .................................................................................................................... 3-6
3.2. 1 Climate Change ........................................................................................................ 3-7
3.2.2 Coastal Storms/Erosion ............................................................................................ 3-9
3.2.3 Contamination/Salt Water Intrusion ........................................................................ 3-11
3.2.4 Dam/Reservoir Failure ............................................................................................ 3-13
3.2.5 Drought ................................................................................................................... 3-21
3.2.6 Earthquake Fault Rupture & Seismic Hazards (Ground Shaking & Liquefaction) ... 3-26
3.2. 7 Flood ....................................................................................................................... 3-40
3.2.8 Geologic Hazards (Expansive Soils & Land Subsidence) ....................................... 3-45
3.2.9 High Winds/Santa Ana Winds ................................................................................. 3-49
3.2. 10 Landslide/Mudflow .................................................................................................. 3-52
3.2. 11 Tsunami .................................................................................................................. 3-57
3.2. 12 Wild land/Urban Fire ................................................................................................ 3-61
3.2.13 Human-Caused Hazards ......................................................................................... 3-66
3.2. 14 Power Outage ......................................................................................................... 3-71
3.3 Vulnerability Assessment ................................................................................................... 3-72
3.3. 1 Asset Inventory ....................................................................................................... 3-73
Final I August 2019
TABLE OF CONTENTS
3.3.2 Estimating Potential Exposure and Losses ............................................................. 3-73
3.3.3 Land Use Development and Trends/Changes in Development .............................. 3-74
3.3.4 Vulnerable Populations ........................................................................................... 3-75
3.4 Summary of Vulnerability ................................................................................................... 3-76
Section 4.0 Mitigation Strategy ....................................................................................................................... 4-1
4.1 Hazard Mitigation Overview ................................................................................................ .4-1
4.1.1 FEMA's National Flood Insurance Program ............................................................. .4-1
4.2 Hazard Mitigation Goals ...................................................................................................... 4-2
4.3 Identify and Prioritize Mitigation Actions ............................................................................. .4-2
4.3.1 Hazard Mitigation Benefit-Cost Review ..................................................................... 4-3
4.4 Regional Considerations ...................................................................................................... 4-6
4.4.1 Regional Fiscal Resources ...................................................................................... .4-7
Section 5.0 Plan Maintenance ......................................................................................................................... 5-1
5.1 Monitoring, Evaluating and Updating the Plan ..................................................................... 5-1
5.1.1 Plan Maintenance ..................................................................................................... 5-1
5.1.2 Plan Evaluation ......................................................................................................... 5-1
5.1.3 Plan Updates ............................................................................................................ 5-2
5.1.4 Adoption .................................................................................................................... 5-3
5.1.5 Implementation Through Existing Programs ............................................................. 5-3
5.1.6 Continued Public lnvolvement... ................................................................................ 5-6
Section 6.0 References .................................................................................................................................... 6-1
APPENDICES
Appendix A Agency Adoption Resolutions
Appendix B Planning Process Documentation
Final I August 2019 11
TABlE OF CONTENTS
Figure 1-1
Figure 3-1
Figure 3-2
Figure 3-3
Figure 3-4
Figure 3-5
Figure 3-6
Figure 3-7
Figure 3-8
Figure 3-9
Figure 3-10
Figure 3-11
Figure 3-12
Final I August 2019
LIST OF FIGURES
Member Agency Participants ........................................................................................................ 1-10
March 17, 2018 PDSI ................................................................................................................... 3-24
July 26, 2014 PDSI ....................................................................................................................... 3-25
Ground Shaking Hazard ............................................................................................................... 3-30
Alquist-Priolo Rupture Zones ........................................................................................................ 3-31
Location of Earthquake Faults Bounding the CDWC Service Area and Orange County .............. 3-34
Liquefaction Susceptibility Zones ................................................................................................. 3-36
Peak Ground Acceleration with 2 Percent Probability in 50 Years for the United States ............. 3-39
Flood Zones ................................................................................................................................. 3-44
Subsidence ................................................................................................................................... 3-47
Landslide Susceptibility ................................................................................................................ 3-56
Tsunami Hazard Zones ................................................................................................................ 3-60
Fire Hazard Severity Zones .......................................................................................................... 3-65
111
TABLE OF CONTENTS
LIST OF TABLES
Table 2-1 DMA 2000 CFR Crosswalk ............................................................................................................. 2-1
Table 2-2 Members of the Planning Team ..................................................................................................... 2-3
Table 2-3 Planning Team Meeting Summary ................................................................................................. 2-6
Table 2-4 Existing Plans and Studies ............................................................................................................. 2-8
Table 3-1 Hazard Identification ....................................................................................................................... 3-2
Table 3-2 Hazard Rankings ............................................................................................................................ 3-4
Table 3-3 Hazard Ranking Methodology ........................................................................................................ 3-5
Table 3-4 Severe and Extreme SC-PDSI Drought Periods 1920-2012
Lasting 12 Months or Longer (Santa Ana, CA) ............................................................................. 3-23
Table 3-5 Palmer Drought Severity lndex ..................................................................................................... 3-23
Table 3-6 Magnitude 5.0 or Greater Earthquakes in the Southern California Region ................................... 3-28
Table 3-7 Characteristics of Important Geologic Faults in Orange County ................................................... 3-33
Table 3-8 Comparison of MMS and Modified Mercalli Intensity Scale .......................................................... 3-37
Table 3-9 Presidential Disaster Declarations for Flooding in Orange County Since 1969 ............................ 3-41
Table 3-10 Major High Wind Events ............................................................................................................... 3-50
Table 3-11 Major Wildfires .............................................................................................................................. 3-62
Table 3-12 Unit Replacement Costs of Facilities ............................................................................................ 3-74
Table 3-13 Summary Assets .......................................................................................................................... 3-77
Table 3-14 Planning Area Critical Facilities and Infrastructure Exposure Costs by Hazard ........................... 3-78
Table 4-1 ST AP LEE Review and Selection Criteria ...................................................................................... .4-5
Final I August 2019 IV
SECTION ONE Introduction
SECTION 1 INTRODUCTION
Across the United States, natural and manmade disasters have led to increasing levels of death, injury,
property damage, and interruption of business and government services. The impact to water and
wastewater utilities and the individuals they serve can be immense and damages to their infrastructure can
result in regional economic and public health consequences. The water and wastewater utilities are
vulnerable to a variety of hazards that can result in damaged equipment, loss of power, disruption to
services, contaminated water supply, and revenue losses. By planning for natural and manmade hazards
and implementing projects that mitigate risk, utilities can reduce costly damage and improve the
reliability of service following a disaster.
As a best practice Orange County water and wastewater agencies have worked together for decades to
improve regional and local reliability and resiliency through joint or collaborative capital improvement
projects, planning processes and emergency management practices. Throughout the county's history the
need for, and development of, water and wastewater services has been driven by the principles of
economies of scale, and limitations of risk by working together among the wholesale and retail water and
wastewater agencies. Below is a brief history of this collaborative process that developed the framework
for this multi-agency plan today.
• In 1921 the Orange County Joint Outfall Sewer (JOS) is formed. Santa Ana and Anaheim agree
to construct an outfall extending into the Pacific Ocean.
• In 1928 the Cities of Anaheim, Fullerton and Santa Ana realized that groundwater supplies were
insufficient to meet the demands of their growing communities, prompting them to join the
Metropolitan Water District of Southern California (MET) in order to get access to water
imported from the Colorado River.
• In 1931 local agencies again recognized the importance of economies in scale by forming the
Orange County Water District (OCWD). One of the goals of OCWD is to protect Orange
County's Santa Ana River water rights from upstream interest.
• Growth in Orange County continued into the 1940's and 1950's when it was realized that the next
increment of supplies was needed. That is when portions of what is now Orange County (outside
of those original three cities) joined MET. MET was formed for much the same reason in that it
was more economical and less risky to pursue importation of water from the Colorado River and
later Northern California as part of a large co-op rather than having each local entity rely on their
own planning and development of water supplies.
• Following a 1946 Board of Supervisor's Orange County Sewerage Survey Report, seven
individual districts combine into the JOS. While individual cities continue to maintain sewage
collection systems, county-wide collections and treatment become a regional operation. And after
several reiterations becoming the Orange County Sanitation District.
• Later, as Orange County continued to develop and expand, these new developments were located
further and further from the MET pipelines bringing water into Orange County. Economically it
was again much more efficient, and less risky, for local members to ban together to participate in
regional pipelines and other water facilities to convey the MET water from where it was available
to where it was needed. Even today, water reliability planning is conducted based on these
original areas, each with its own supply reliability risk profile. The three areas are:
Final I August 2019
1. Brea/La Habra service area -have about 80% of their supplies are from Cal Domestic
Water Company groundwater sources in San Gabriel Valley.
1-1
SECTION ONE Introduction
2. Orange County Water District service area -gets about 75% of their supplies from
groundwater sources
3. South Orange County service area -has few local resources, thereby requiring the import
of about 95% of their potable water demands
• In 1983 the Volunteer Emergency Preparedness Organization (VEPO) was formed, creating a
mutual aid agreement and communications system for Orange County's 33 water utilities to work
together.
• Following the 1994 Northridge Earthquake and subsequent Standardized Emergency
Management System in 1996, OC water agencies recognized the need to staff the VEPO program
as a shared service to support its member agency's disaster readiness.
• VEPO was renamed to the Water Emergency Response Organization of Orange County
(WEROC) in 1999 to better reflect its goal and purpose.
• The agency known today as the South Orange County Wastewater Authority (SOCWA) was
formed in 2001 when the South East Regional Reclamation Authority (SERRA), Aliso Water
Management Agency (A WMA) and South Orange County Reclamation Authority (SOCRA)
consolidated to meet the wastewater needs of more than 500,000 homes and businesses across
South Orange County.
• In 2006 WEROC staff realized the importance of including wastewater agencies in its program,
as many of its water utilities also provided wastewater services and that the sectors had similar
resources that could support each other. With this change, the program welcomed in wastewater
agencies and grew to support 37 agencies in total.
• In 2008 the internationally awarded Ground Water Replenishment System (GWR) was
completed. This was a joint project of the Orange County Water District and the Orange County
Sanitation District enhancing reliability for all of the county.
As has been demonstrated throughout the history of Orange County, the principles of banding together
with neighboring interests to create joint regional infrastructure, connected systems and economies of
scale has been applied time and time again. Working together to develop a multi-jurisdictional hazard
mitigation plan focused on the agencies (cities and special districts) that provide drinking water and
wastewater services came from an already standing practice of regional planning and coordination to
improve resiliency and response. Additionally, it gave the participating agencies the opportunity to focus
on risk as it applies specifically to these services and not all of their jurisdiction's services.
In 2005, WEROC started to work with its member agencies, CalOES and FEMA to fund the first multi-
jurisdictional plan through a Hazard Mitigation Planning Grant. In 2007, with the assistance of the
Mitigation Grant, the Municipal Water District of Orange County (MWDOC) along with 20-member
agencies prepared a Multi-Jurisdictional Hazard Mitigation Plan (HMP or Plan) that identified critical
water and wastewater facilities in the county, and mitigation actions in the form of projects and programs
to reduce the impact of natural and manmade hazards on these facilities. The vision of a plan that takes
into consideration regional and local infrastructure and how it works together while building it stronger,
supported other planning efforts such as the South Orange County Reliability Study and later the Orange
County Reliability Study.
This plan builds on the original 2007 Plan and a previous update approved in 2012. MWDOC was joined
in this current update by 18 participating water and wastewater utilities, hereafter, referred to as Member
Agencies (MA), that serve communities in Orange County, California. The Plan was prepared with input
from county residents, orange county emergency managers, and with the support of the California
Governor's Office of Emergency Services (Cal OES) and the Federal Emergency Management Agency
Final I August 2019 1-2
SECTION ONE Introduction
(FEMA). The process to develop the Plan included five planning team meetings and coordination with
representatives from MWDOC and each participating MA.
The Plan is a guide for MWDOC and the MAs over the next five years toward greater disaster resistance
in harmony with the character and needs of the local community and the MAs. The Plan focuses on
participating water and wastewater facilities in the county and identifies mitigation actions to reduce the
impact of natural and manmade hazards on critical facilities. In addition, each agency will utilize current,
approved planning documents that identify implementation strategies for capital improvement, risk
reduction, system upgrades, and operations. These documents complement the Plan and include but are
not limited to: All Hazards SEMS/NIMS Emergency Response Plans, capital improvement plans, and
asset management plans.
The Plan is a working document that will grow and change as our communities and MAs do. This means
at times participating agencies may identify a higher priority than noted in this Plan, or a redirection of
goals based on current information or updated decisions. In consideration of this concept, there may be
projects or policies that need to be considered that were not included in this document. These changes
will be documented during the Plan implementation and formal updates to the Plan will be made every
five years as required.
1.1 PURPOSE OF THE PLAN AND AUTHORITY
Federal legislation has historically provided funding for disaster relief, recovery, and some hazard
mitigation planning. The Disaster Mitigation Act of 2000 (DMA 2000) is the latest legislation to improve
this planning process (Public Law 106-390). This legislation reinforces the importance of mitigation
planning and emphasizes planning for disasters before they occur. As such, DMA 2000 establishes a pre-
disaster hazard mitigation program and new requirements for the national post-disaster Hazard Mitigation
Grant Program (HMGP). The Pre-Disaster Mitigation Act of 2010 was signed into law in January of
2011 but does not impact the planning process. The 2010 Act reauthorizes the pre-disaster mitigation
program.
Section 322 of DMA 2000 specifically addresses mitigation planning at the state and local levels. It
identifies the requirements that allow HMGP funds to be used for planning activities and increases the
amount of HMGP funds available to states that have developed a comprehensive, enhanced mitigation
plan prior to a disaster. States and communities must have an approved mitigation plan in place prior to
receiving pre-or post-disaster funds. Local mitigation plans must demonstrate that their proposed
mitigation measures are based on a sound planning process that accounts for the risk to and the
capabilities of the individual communities.
DMA 2000 is intended to facilitate cooperation between state and local authorities, prompting them to
work together. It encourages and rewards local and state pre-disaster planning and promotes
sustainability as a strategy for disaster resistance. This enhanced planning network is intended to enable
local and state governments to articulate accurate needs for mitigation, resulting in faster allocation of
funding and more effective risk reduction projects.
FEMA prepared the Final Rule, published in the Federal Register on September 16, 2009 (Code of
Federal Regulations (CFR) at Title 44, Chapter 1, Part 201 (44 CFR Part 201and206)), which establishes
planning and funding criteria for states and local communities.
Final I August 2019 1-3
SECTION ONE Introduction
For federal approval, the following criteria must be met during the planning process:
• Complete documentation of the planning process.
• Detailed risk assessment of hazard exposures in the community and water and wastewater
infrastructure.
• Comprehensive mitigation strategy, describing goals and objectives, proposed strategies,
programs and actions to avoid long-term vulnerabilities.
• A planned maintenance process will describe the method and schedule of monitoring, evaluating
and updating the plan, and the integration of the Plan into other planning mechanisms.
• The formal adoption of the governing bodies of each participating jurisdiction.
• Plan review by both Cal OES and FEMA.
As the cost of recovering from natural disasters continues to increase, the MAs realize the importance of
identifying effective ways to reduce vulnerability to disasters. Hazard mitigation plans assist
communities in reducing risk from natural hazards by identifying resources, information, and strategies
for risk reduction, while guiding and coordinating mitigation activities.
The Orange County Water and Wastewater Hazard Mitigation Plan (HMP or Plan) provides a framework
for participating water and wastewater utilities to plan for natural and man-made hazards in Orange
County. The resources and information within the Plan will allow participating jurisdictions to identify
and prioritize future mitigation projects, meet the requirements of federal assistance programs and grant
applications, and encourage coordination and collaboration in meeting mitigation goals.
The Plan is intended to serve many purposes, including:
• Enhance Public Awareness and Understanding -To help county residents better understand the
natural and man-made hazards that threaten public health, safety, and welfare; economic vitality;
and the operational capability of important facilities;
• Create a Decision Tool for Management -To provide information so that water and wastewater
managers and leaders of local government may act to address vulnerabilities;
• Enhance Local Policies for Hazard Mitigation Capability -To provide the policy basis for
mitigation actions that will create a more disaster-resistant future;
• Provide Inter-Jurisdictional Coordination o(Mitigation-Related Programming -To ensure that
proposals for mitigation initiatives are reviewed and coordinated among MWDOC and MAs; and
• Promote Compliance with State and Federal Program Requirements -To ensure that MWDOC
and MAs can take full advantage of state and federal grant programs, policies, and regulations.
To qualify for certain forms of federal aid for pre-and post-disaster funding, local jurisdictions must
comply with the federal OMA 2000 and its implementing regulations. The Plan has been prepared to
meet FEMA and Cal OES requirements, thus making MWDOC and the participating MAs eligible for
funding and technical assistance for State and federal hazard mitigation grant programs.
DMA 2000 requires local hazard mitigation plans, including this Plan, to be updated every five years.
This means that the Plan is designed to carry the MAs through the next five years, after which its
assumptions, goals, and objectives will be revisited, updated, and resubmitted for approval.
Final I August 2019 1-4
SECTION ONE Introduction
1.2 MULTI-JURISDICTIONAL PARTICIPATION
1.2.1 Overview of Water and Wastewater Systems in Orange County
Water distribution and wastewater collection and treatment in Orange County involves dozens of agencies
and utilities working together, and relies on integrated, regional systems and facilities. There are several
retail water and wastewater utilities in Orange County, each with its own distinct service area and sources
of potable water. The retail water agencies include water districts and city water departments.
The Municipal Water District of Orange County (MWDOC) is a wholesale water supplier and resource
planning agency that serves all of Orange County (except Anaheim, Fullerton, and Santa Ana) through 28
retail water agencies. MWDOC purchases imported water from the Metropolitan Water District of
Southern California (Metropolitan) for distribution to its member agencies, which provide retail water
services to the public. Local supplies meet more than half of Orange County's total water demand. To
meet the remaining demand, MWDOC purchases imported water from northern California (through the
State Water Project) and the Colorado River. This water is provided by Metropolitan, which in addition
to Orange County, also serves Ventura, Los Angeles, San Bernardino, Riverside, and San Diego
ecmnties.1
Local water supplies in Orange County vary regionally and include groundwater, recycled wastewater,
and surface water. Water supply resources in MWDOC's service area include groundwater basins, which
provide a reliable local source and are also used as reservoirs to store water during wet years and draw
from storage during dry years. Recycled water and surface water provide an additional local source to
some MWDOC retail agencies, with surface water captured mostly from Santiago Creek into Santiago
Reservoir.2
The Orange County Water District (OCWD) manages and replenishes the Orange County Groundwater
Basin (Basin), ensures water reliability and quality, prevents seawater intrusion, and protects Orange
County's rights to Santa Ana River water. The Basin contains approximately 500,000 acre-feet of usable
storage water and covers 270 square miles. The Basin is a reliable source of water and provides
approximately 75 percent of north and central Orange County's water supply, as south Orange County is
virtually 100 percent dependent on imported water.3
MWDOC and OCWD work cooperatively and continue to evaluate new and innovative programs,
including seawater desalination, wetlands expansion, recharge facility construction, surface storage, new
water use efficiency programs, and system interconnections for enhanced reliability.
Wastewater collection and treatment in Orange County is managed by two regional agencies: The Orange
County Sanitation District (OCSD) and the South Orange County Wastewater Authority (SOCWA).
OCSD and SOCWA, which cover north and central Orange County and south Orange County,
respectively, are responsible for the trunk line collection, treatment, biosolids management, and ocean
outfalls for treated wastewater disposal. OCSD has two primary treatment facilities and SOCW A has
three primary treatment facilities that treat wastewater from residential, commercial and industrial
sources.
1 Municipal Water District of Orange County, 2015 Urban Water Management Plan, May 2016.
2 Ibid.
3 Orange County Water District, OCWD Brochure, July 2017.
Final I August 2019 1-5
SECTION ONE Introduction
1.2.1.1 Potable Water Supplies -Current and Future
Potable water demand for Orange County was about 485,000 acre-feet per year (AF/yr) in 2017. The
County's population is projected to rise from 3.1 million to 3.7 million people by 2025, and potable water
demand is projected to rise at just about the same rate to about 575,000 AF/yr.
With planned local water-supply projects plus the continued availability of Metropolitan water to
replenish the OCWD Basin, demand projections show a 12 percent decrease in demand for imported, full-
service Metropolitan water by 2025. If the local projects do not get built or produce less than planned or
are merely delayed, then additional Metropolitan water will be needed.
1.2.2 Participating Jurisdictions
Following is a list of the jurisdictions (MAs) participating in the Plan update; refer to Figure 1-1. This list
is organized first by the four utilities that have regional management responsibilities that extend to several
water districts or city utilities and then by local water retail utilities:
• Municipal Water District of Orange County
• Orange County Water District
• Orange County Sanitation District
• South Orange County Wastewater Authority
• City of Buena Park (Utilities Division)
• El Toro Water District
• City of Garden Grove Water Division
• City of La Habra (Water Division and Wastewater Division)
• Laguna Beach County Water District
• Mesa Water District
• Moulton Niguel Water District
• City of Newport Beach (Utilities Department)
• City of Orange (Water and Wastewater Division)
• Santa Margarita Water District
• Serrano Water District
• South Coast Water District
• Trabuco Canyon Water District
• City of Westminster (Water Division)
• Yorba Linda Water District
• Garden Grove Sanitary District
It should be noted that the City of Tustin was a participant in the original 2007 Plan and 2012 Update;
however, the City is not a participant in the 2018 Update. It should also be noted that the Cities
participating in the Plan did not represent all of the services of that city, but rather only the services noted
being water or/and wastewater. This focus was purposeful to support the collaboration of these services
on a regional and local level. Additionally, the city services participating are typically "enterprise funds,"
which allowed for those services to participate in a hazard mitigation process regardless of whether the
entire city could support the planning process fiscally through funding and staff commitments.
Final I August 2019 1-6
SECTION ONE Introduction
Retailers can be grouped into the following three regions based on the availability of local groundwater
resources:
• The Basin provides approximately 75 percent of north and central Orange County's water supply.
The rest of their supply is primarily imported water provided by Metropolitan; although Serrano
Water District and the City of Orange are partly served by local runoff captured in Irvine Lake.
Participating MAs within the Basin include the water departments for the cities of Buena Park,
Garden Grove, Newport Beach, Orange, and Westminster and the Mesa, Serrano, and Yorba
Linda water districts.
• South Orange County is almost 100 percent dependent on Metropolitan for its potable water
supply. Parts of this area are within the San Juan Capistrano Groundwater Basin, which is
managed by the San Juan Basin Authority. Local groundwater in the area is high in salts and
accounts for less of the water supply than utilities in the OCWD Basin. MAs include El Toro,
Laguna Beach County, Moulton Niguel, Santa Margarita, South Coast, and Trabuco Canyon
water districts.
• The Brea/La Habra region receives groundwater from the San Gabriel Basin in Los Angeles
County through the California Domestic Water Company and from Metropolitan. Of the two
utilities in the region, the City of La Habra is a MA. The city also operates a small groundwater
well.
Although located within Orange County, the participating MAs do not comprise or serve the entire
County. In addition, the service areas for each of the MAs participating in the Plan do not necessarily
align with incorporated or unincorporated boundaries or city boundaries. In many cases a MA may serve
multiple cities and/or portions of cities/unincorporated areas. This includes even the city MA further
contributing to why some city MA choose to participate in a sector specific hazard mitigation
plan process. Profiles for each of the participating water and wastewater utilities are provided in the
Jurisdictional Annexes.
The Plan must be formally adopted by each jurisdiction's governing body, which may be the Board of
Directors for each agency and districts and the City Council for each city water and/or wastewater
department. In order to meet the FEMA guidelines for mitigation plans to address a jurisdiction in its
entirety, the participating cities have a current adopted, or are in the process of completing, a single-
jurisdiction local hazard mitigation plan in effect for the entire city. In these cases, it has been incumbent
upon the individual cities and their decision-makers to decide how best to integrate elements of this Plan
into its overall mitigation strategy and other existing plans and processes. Information on each
participating city's single-jurisdiction mitigation plan has been provided within their respective annex for
cross-reference. It is recognized that eligibility for hazard mitigation grant funding for the city water
and/or wastewater services within this plan, will occur through an approved and adopted city-wide
mitigation plan.
The resources and background information in the Plan are applicable countywide, providing the
groundwork for goals and recommendations for other local mitigation plans and partnerships. In the
identification of shared action items, the Plan fosters the development of partnerships and implementation
of preventative activities. A unified, multi-jurisdictional plan will ensure that any proposals for
mitigation initiatives are reviewed and coordinated among the participating agencies and utilities.
Final I August 2019 1-7
SECTION ONE Introduction
1.3 WHAT IS NEW/WHAT HAS CHANGED FROM THE 2012 PLAN
Several sections of the 2018 Plan update have been modified from the original 2007 Plan and 2012 Plan
update, including the use of annexes for each of the participating jurisdictions. Changes made to specific
sections of the Plan are summarized below:
Several sections of the 2018 Plan update have been modified and reorganized from the original 2007 Plan
and 2012 Plan update, including the use of annexes for each of the participating jurisdictions. Changes
made to specific sections of the Plan are summarized below:
• Section One: Section One has been significantly modified to move profile information specific to
each participating jurisdiction to the Jurisdictional Annexes. Text has also been modified to
clarify the multi-jurisdictional involvement, updated outdated or irrelevant information, and to
streamline the section. This subsection, what is new/what has changed from the 2012 plan, has
also been added.
• Section Two: Section Two now documents the Planning Process. This section has been
completely revised and updated to discuss the process for the Plan update, including the Planning
Team, meetings, public outreach, and overall process for the Plan update.
• Section Three: Section Three now comprises the Risk Assessment. The hazards have been
updated to reflect hazards that affect the planning area, as determined by the Planning Team.
This includes the removal of tomados and extreme heat (included in the 2012 plan) and the
addition of power outage and climate change. In some cases, the hazards were reorganized or
combined under a primary heading, such as Geologic Hazards, which includes expansive soils
and land subsidence and Seismic Hazards, which include fault rupture, ground shaking and
liquefaction. Each of the hazard profiles were updated to reflect hazard occurrences (if any) since
the 2012 plan was prepared.
In preparation of the 2018 Plan update, infrastructure mapping for each of the MAs was
completed. An independent consultant working directly with MWDOC (who coordinated with
the MAs ), updated water and wastewater infrastructure information for each MA. As part of the
2018 Plan update, these critical facilities were overlaid with mapped hazard areas to determine
which assets are in each hazard area and to assess overall vulnerabilities.
• Section Four: Section Four now documents the Mitigation Strategy. This section was renamed
and includes overarching hazard mitigation goals for the planning area. It was determined
through the Planning Team meetings that mitigation goals are similar for all participating
jurisdictions and therefore one set of goals were developed. Some participating jurisdictions
identified additional goals specific to their agencies, which have been included in the respective
Jurisdictional Annex. Updated mitigation actions and capabilities assessments specific to each
participating jurisdiction have been moved to the Jurisdictional Annexes. An overview of hazard
mitigation is provided, including the methodology for identifying and prioritizing mitigation
actions.
• Section Five: Section Five now documents the Plan Maintenance process. This section involves
minor modifications and updates.
Final I August 2019 1-8
SECTION ONE Introduction
• Section Six: Section Six now documents the Plan references and has been updated to reflect
references used in preparation of the 2018 Plan update.
• Jurisdictional Annexes: The Jurisdictional Annexes are new to the Plan update. An annex is
provided for each MA and includes updated components of the hazard mitigation plan that are
specific to each jurisdiction.
• Appendices: The Appendices have been completely updated to include 2018 Plan update
materials.
1.4 PLAN ORGANIZATION
The Orange County Regional Water and Wastewater HMP is organized into the following sections:
• Section One -Introduction: Provides an overview of the Plan, a discussion of the Plan's purpose
and authority, a description of the multi-jurisdictional participation, a summary of how this
update differs from previous versions of the Plan and describes the Plan's organization.
• Section Two -Planning Process Documentation: Describes the HMP planning process, as well
as the meetings and outreach activities undertaken to engage the MAs and the public.
• Section Three -Risk Assessment: Identifies and profiles the hazards that threaten the area served
by the MAs and identifies the vulnerability and risk to critical water and wastewater infrastructure
associated with each hazard. Due to the vast planning area associated with the MAs participating
in the Plan, this section addresses the entire geographic area served by the MAs. The
Jurisdictional Annexes detail the hazards, risk assessments, and mitigation strategies specific to
each MA.
• Section Four -Mitigation Strategy: Includes multi-jurisdictional goals for the 2018 Plan and
summarizes the mitigation action plan process. Mitigation actions and capabilities specific to
each MA are detailed in the Jurisdictional Annexes.
• Section Five -Plan Maintenance: Discusses how the 2018 Plan update will be monitored,
evaluated, and updated over the next five years.
• Section Six -References: Identifies the resources used in preparation of the 2018 Plan update.
• Jurisdiction Annexes: Provides a profile of the jurisdiction, describe the hazards, assess the
vulnerabilities, identify the capabilities, and describe the mitigation strategy specific to each
participating jurisdiction.
• Appendices: Provides the 2018 Plan update materials.
Sections one through seven comprise the primary HMP. It describes the Plan, multi-jurisdictional
planning process, and hazard mitigation planning requirements for each MA. The information in these
sections are applicable to all the MAs. The Jurisdictional Annexes provide hazard mitigation planning
information specific to each MA and supplements the information contained in the other sections.
Final I August 2019 1-9
SECTION ONE
LOS ANGELES
PACIFIC OCEAN
LEGEND
Participating Water Districts
(-< > ::,j Participating Sanitary Districts
r7/l ParticipatlngWater LLL'.J &SanitaryDistricts .-----, L ____ J MWDOCServlceArea
Final I August 2019
Figure 1-1
Member Agency Plan Participants
OCWD Service Area
OCSDServiceArea
SOCWA Service Area
2.5
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SAN
BERNARDINO
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___ J
Introduction
RIVERSIDE
SAN DIEGO
1-10
SECTION TWO Planning Process Documentation
SECTION 2 PLANNING PROCESS DOCUMENTATION
This section describes each stage of the planning process used to update the Multi-Hazard Mitigation Plan
(Plan). The planning process provides a framework to document the Plan's update and follows the
FEMA-recommended steps. The Plan update follows a prescribed series of planning steps, which
includes organizing resources, assessing risk, updating the mitigation actions, updating the Plan,
reviewing and revising the Plan, and adopting and submitting the Plan for approval. Each step is
described in this section.
Hazard mitigation planning in the United States is guided by the statutory regulations described in the
DMA 2000 and implemented through 44 Code of Federal Regulations (CFR) Parts 201 and 206.
FEMA' s hazard mitigation plan guidelines outline a four-step planning process for the development and
approval of Hazard Mitigation Plans (HMPs). Table 2-1, DMA 2000 CFR Crosswalk, lists the specific
CFR excerpts that identify the requirements for approval.
Table 2-1
DMA 2000 CFR Crosswalk
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<>'• '·:·J·:<•'•::' ·" · •. •, ' . .. .. ..............
(1) Organize Resources Section 3
201.6(c)(1) Organize to prepare the plan
201.6(b)(1) Involve the public
201.6(b)(2) and (3) Coordinate with other agencies
(2) Assess Risks Section 4
201.6(c)(2)(i) Assess the hazard
201.6(c)(2)(ii) and (iii) Assess the problem
(3) Develop the Mitigation Plan Section 5
201.6(c)(3)(i) Set goals
201.6(c)(3)(ii) Review possible activities (actions)
201.6(c)(3)(iii) Draft an action plan
(4) Plan Maintenance Section 6
201.6(c)(5) Adopt the plan
201.6(c)(4) Implement, evaluate, and revise
As documented in the corresponding sections, the planning process for the 2018 Plan update is consistent
with the requirements for hazard mitigation planning with customizations, as appropriate. All basic
federal guidance documents and regulations are met through the customized process.
2.1 ORGANIZING RESOURCES
One of the first steps in the planning process involved organization of resources, including identifying the
Project Management Team, and convening the Hazard Mitigation Plan Planning Team (Planning Team)
and performing document review.
Final I August 2019 2-1
SECTION TWO Planning Process Documentation
2.1.1 PROJECT MANAGEMENT TEAM
The Project Management Team was responsible for the day-to-day coordination of the Plan update work
program, including forming and assembling the Planning Team; scheduling Planning Team meetings;
preparing, reviewing, and disseminating Planning Team meeting materials; coordinating, scheduling, and
participating in community engagement activities and meetings; and coordinating document review. The
Project Management Team was led by an Emergency Coordinator from the Water Emergency Response
Organization of Orange County (WEROC), administered by the Municipal Water District of Orange
County (MWDOC), who served as Project Manager and participated on the Planning Team. The Project
Manager monitored planning progress and met with participating jurisdictions as needed to assist with
obtaining and updating information for the Plan. The Project Management Team also included the
Emergency Manager from WEROC/MWDOC, who served as the Project Manager for the 2012 Plan
update and provided guidance as well as historical insight and knowledge associated with the 2012 Plan.
The Project Management Team worked directly with the Consultant Project Management Team
throughout development of the Plan update. The Consultant Team, consisting of a variety of hazard
mitigation/planning professionals, provided guidance and support to MWDOC and the Planning Team
through facilitation of the planning process, data collection, community engagement, and meeting
material and document development.
2.1.2 PLANNING TEAM
The planning process for the Plan update involved ten water districts, two regional wastewater agencies,
and the water departments for eight cities; a total of 20 jurisdictions participated in the planning process.
Representatives from all Member Agencies (MA) provided input into the Plan update process. Each of
the MA provided at least one representative to participate on the Planning Team and attend meetings.
Each local team, made up of other jurisdictional staff/officials, met separately and provided additional
local-level input to the Planning Team representative for inclusion into the Plan. The MA participated in
the planning process by exchanging information, discussing planning strategies, sharing goals, resolving
issues, and monitoring progress. The MA benefited from working closely together because many of the
hazards identified are shared by neighboringjurisdictions and participants were involved in the discussion
of potential mitigation actions. Jurisdictional representatives included but were not limited to utility
engineers, planners, and emergency management officers.
The Planning Team worked together to ensure the success of the planning process and is responsible for
its implementation and future maintenance. The Planning Team's key responsibilities included:
• Participation in Planning Team meetings.
• Coordination of jurisdiction-specific meetings to relay information and obtain input.
• Collection of valuable local information and other requested data.
• Decision on plan process and content.
• Development and prioritization of mitigation actions for the Plan.
• Review and comment on Plan drafts.
• Coordination and involvement in the public engagement process.
Table 2-2, Members of the Planning Team, identifies the Planning Team members and their roles in the
Plan update.
Final I August 2019 2-2
SECTION TWO Planning Process Documen1a1ion
Table 2-2
Members of the Planning Team
Nme TllelRofe Organization Planning Team Role
Project Manager/Planning Team
Representative -Organization of Planning
Emergency Programs T earn and meetings, development of and
Francisco Soto Coordinator/Plan Update WEROC/MWDOC participation in community outreach,
Project Manager hazard identification, capabilities
assessment, goal development, mitigation
actions and prioritization, plan coordination
and review.
Project Management T earn -Historical
knowledge and insight into 2012 Plan,
Kelly Hubbard WEROC Programs WEROC/MWDOC overall guidance on 2018 Plan update,
Manager hazard identification, capabilities
assessment, goal development, mitigation
actions and prioritization, plan review.
Assistant General Hazard identification, capabilities
Karl Seckel Manager MWDOC assessment, goal development, mitigation
actions and prioritization, plan review.
Orange County Water Hazard identification, capabilities
Paula Bouyounes Risk and Safety Manager District assessment, goal development, mitigation
actions and prioritization, plan review.
Safety and Health Orange County Sanitation Hazard identification, capabilities
Rod Collins Supervisor District assessment, goal development, mitigation
actions and prioritization, plan review.
Human Resources/Risk Orange County Sanitation Hazard identification, capabilities
Richard Spencer Manager District assessment, goal development, mitigation
actions and prioritization, plan review.
Environmental Compliance South Orange County Capabilities assessment, goal
Sean Peacher Safety Risk Manager Wastewater Authority development, mitigation actions and
prioritization, plan review.
Bill Paddock Supervising Mechanic South Orange County Hazard identification.
Wastewater Authority
Hazard identification, capabilities
Michael Grisso Utilities Manager City of Buena Park assessment, goal development, mitigation
actions and prioritization, plan review.
Public Relations/ Hazard identification, capabilities
Sherri Seitz Emergency Preparedness El Toro Water District assessment, goal development, mitigation
Administrator actions and prioritization, plan review.
Rick Olson Operations Superintendent El Toro Water District Hazard identification, capabilities
assessment.
Senior Administrative Hazard identification, capabilities
Katie Victoria Analyst City of Garden Grove assessment, goal development, mitigation
actions and prioritization, plan review.
Raquel Manson Senior Administrative City of Garden Grove Hazard identification, capabilities
Analyst assessment.
Final I August 2019 2-3
SECTION TWO Planning Process Documentation
Name
A.J. Holmon
Brian Jones
Leo Lopez
Kaying Lee
Tracy lngebrigtsen
Dan West
Kevin Crawford
Todd Novacek
Casey Parks
Steffen Catron
Mark Ouellette
Chris Lopez
Daniel Peterson
Jerry Vilander
Trisha Woolslayer
Lorrie Lausten
Becky Rodstein
Final I August 2019
Table 2-2 [continued]
Members of the Planning Team ,.... Ofpnizatiolll Pta.ingTeamRole
Streets/Environ mental City of Garden Grove Hazard identification.
Division Manager
Water and Sewer Manager City of La Habra Hazard identification, mitigation actions and
prioritization.
Laguna Beach Water Hazard identification, capabilities
Safety Officer District assessment, goal development, mitigation
actions and prioritization, plan review.
Water Quality and Hazard identification, capabilities
Mesa Water District assessment, goal development, mitigation Compliance Supervisor actions and prioritization, plan review.
Safety and Compliance Moulton Niguel Water Hazard identification, capabilities
assessment, goal development, mitigation Coordinator District actions and prioritization, plan review.
Water Distribution Moulton Niguel Water Hazard identification, capabilities
Supervisor District assessment.
Operator Moulton Niguel Water Hazard identification.
District
Director of Operations Moulton Niguel Water Hazard identification.
District
Water Production Hazard identification, capabilities
Supervisor City of Newport Beach assessment, goal development, mitigation
actions and prioritization, plan review.
Utilities Manager City of Newport Beach Hazard identification, mitigation actions and
prioritization, plan review.
Hazard identification, capabilities
Supervisor City of Orange assessment, goal development, mitigation
actions and prioritization, plan review.
Santa Margarita Water Hazard identification, capabilities
Safety Specialist assessment, goal development, mitigation District actions and prioritization, plan review.
Operations Business Santa Margarita Water Hazard identification.
Manager District
Hazard identification, capabilities
General Manager Serrano Water District assessment, goal development, mitigation
actions and prioritization, plan review.
Environmental Health and Hazard identification, capabilities
Safety Manager South Coast Water District assessment, goal development, mitigation
actions and prioritization, plan review.
Trabuco Canyon Water Hazard identification, capabilities
Principal Engineer District assessment, goal development, mitigation
actions and prioritization, plan review.
Hazard identification, capabilities
Administrative Analyst City of Westminster assessment, goal development, mitigation
actions and prioritization, plan review.
2-4
SECTION TWO Planning Process Documen1a1ion
Name Tiie/Roie
Table 2-2 [continued]
Members of the Planning Team
Ofgaaizatiua. Planning Team Role
Hazard identification, capabilities
Anthony Manzano Senior Project Manager Yorba Linda Water District assessment, goal development, mitigation
actions and prioritization, plan review.
Orange County Sheriff's Overview and perspective of the plan
Ethan Brown Senior Program Department Emergency preparation process and review;
Coordinator information relevant to their area of Management expertise.
It should be noted that although 20 MA participated in the Plan, all MWDOC's 28 MA were invited to
participate in the Plan either through an Annex or as part of the Planning Team. In addition, through the
Orange County Emergency Management Organization (OCEMO), the County of Orange, and all cities
within the county were provided the opportunity to participate in the Plan process, including
dissemination of the Draft Plan to OCEMO's distribution list for review and comment. This includes all
Orange County cities, colleges, and school districts; special districts; water districts; State and county
agencies; hospital association; affiliates and other approved agencies; refer to Appendix B.
MWDOC also provided an opportunity for State and county agencies and emergency services providers
to be part of the Planning Team. Email invitations were extended to the following:
• State Water Resources Control Board
• Orange County Health Care Agency
• Orange County Fire Agency
• Orange County Sheriffs Department
Businesses, academia and other private and non-profit interests were provided notification of the Draft
Plan's availability via the MA email distribution and notification lists and social media. Distribution
documentation will be provided in Appendix B of the Final Plan.
The Planning Team held five meetings. The meetings were designed to aid the MA in completing a
thorough review of the hazards within their jurisdictions, identifying capabilities, understanding and
assessing vulnerabilities, and identifying mitigation strategies. Table 2-3, Planning Team Meeting
Summary, provides a summary of the meetings. Meeting materials, including PowerPoint presentations,
sign-in sheets, agendas, notes, and other relevant handouts are provided in Appendix B.
Final I August 2019 2-5
SECTION TWO Planning Process Documentation
Table 2-3
Planning Team Meeting Summary
Date Meeting Discussioa ·. '
July 26, 2017 Planning Team Meeting #1 • Introductions
• Project goals and objectives
• Roles and responsibilities
• Data/information needs
• Plan Update and requirements
• Preliminary discussion of community engagement strategy
• Hazard identification and prioritization
• Meeting schedule
August 30, 2017 Planning Team Meeting #2 • Summary of hazard profiles
• Risk assessment methodology
• Capabilities assessment
• Community engagement update
• Data/information needs
September 27, 2017 Planning Team Meeting #3 • Review/update of goals
• Discussion of mitigation actions
• Community engagement update
• Capabilities assessment
• Data/information needs
January 23, 2018 Planning Team Meeting #4 • Overview of process
• Public involvement and survey results
• Overview of vulnerability/risk assessment
• Discussion of hazard mapping
• Schedule for plan review and submittal
April 11 , 2018 Planning Team Meeting #5 • Review of Draft Plan
• Discussion of comments and revisions
April11,2019 Planning Team • Meeting with specific MA to address comments from FEMA
In addition to the regularly scheduled meetings, Planning Team members coordinated individually with
the Plan Update Project Manager, as necessary, to resolve any questions or discuss information requested
at the Planning Team meetings. This was typically accomplished via telephone or email. Any MA that
missed a scheduled planning meeting coordinated with the Project Manager separately to review what
was discussed in the meeting and to obtain jurisdiction-specific information. The City of Orange was not
able to participate directly in the scheduled Planning Team meetings and met separately with the Plan
Update Project Manager to review items discussed at the meetings and provide information necessary for
the Plan update.
2.1.3 PUBLIC OUTREACH
A public outreach and engagement strategy was developed to inform the public and maximize public
involvement in the Plan update process. The public outreach strategy included posting information on the
MA websites, email and social media distribution, community survey, and presentations at the Orange
County Business Council and Orange County Emergency Management Organization meetings, as
described below; refer to Appendix B.
Final I August 2019 2-6
SECTION TWO Planning Process Documentation
MEMBER AGENCY WEBSITES
Information regarding the Plan update was made available on each MA website. The webpages provided
information on the Plan, the Plan update process, and how the public can be involved in the planning
process, including a link to the community survey (discussed below). A link to the draft Plan was also
made available for review and comment.
SOCIAL MEDIA
Social media notifications regarding the Plan update, including a link to the community survey were sent
to MA social media accounts.
COMMUNITY SURVEY
A community survey was developed to obtain input from the community about various hazard mitigation
topics. The survey was designed to help the MA gauge the level of knowledge the community has about
natural disaster issues and to obtain input about areas of the County that may be vulnerable to various
types of natural disasters. The information provided was used to identify and coordinate projects focused
on reducing the risk of injury or damage to property from future hazard events. A link to the survey was
provided on each of the MA websites. Twenty surveys were completed.
STAKEHOLDER OUTREACH
Orange County Business Council -August 8, 2017
The Plan Update Project Manager presented to the Orange County Business Council during their monthly
meeting. Francisco presented about hazard mitigation, the planning process, hazards affecting Orange
County water and wastewater infrastructure, and the importance of their involvement in the development
process. Participants of this meeting were extended the opportunity to be part of the Planning Team
and/or provide information and input through the process, including:
• Orange County Transportation Authority (OCT A)
• Metropolitan Water District of Southern California (Metropolitan)
• Southern California Association of Governments (SCAG)
• California Department of Transportation (Caltrans)
• Transportation Corridor Agency (TCA)
Orange County Emergency Management Organization -April 5, 2018
The Plan Update Project Manager presented to the OCEMO during their monthly meeting. OCEMO is a
subcommittee comprised of the County of Orange and all subdivisions that ensure the cooperative
maintenance of the Operational Area Emergency Operations Plan, policies and procedures, training and
exercises. Francisco presented about hazard mitigation, the planning process, hazards affecting Orange
County water and wastewater infrastructure, and the importance of their involvement in the development
process. As noted previously, the Draft Plan was disseminated to OCEMO's distribution list for review
and comment; refer to Appendix B.
Final I August 2019 2-7
SECTION TWO Planning Process Documentation
Public Review Draft Hazard Mitigation Plan
The public review draft Plan was made available to the public for review and comment for a 30-day
period beginning August 10, 2018 and concluding on September 10, 2018. The draft Plan was made
available on the MA webpages and at the MA offices and/or front counters. Information was provided on
how to submit comments or ask questions regarding the draft Plan.
2.1.4 REVIEW AND INCORPORATE EXISTING INFORMATION
The Planning Team and each MA local team reviewed and assessed existing plans and studies available
from local, state, and federal sources during the planning process. The types of documents reviewed and
incorporated as part of the Plan update are listed in Table 2-4, Existing Plans and Studies. Due to the
number of MA involved in the Plan update, similar plans and studies (e.g., General Plans, Municipal
Codes, Urban Water Management Plans) specific to each jurisdiction were reviewed and incorporated in
the Plan update. A complete list ofreferences is included in Section 7.0, References.
2.2 ASSESS RISKS
In accordance with FEMA requirements, the Planning Team identified and prioritized the hazards
affecting the County and assessed the associated vulnerability from those hazards. Results from this
phase of the planning process aided subsequent identification of appropriate mitigation actions to reduce
risk from these hazards; refer to Section 3.0.
Table 2-4
Existing Plans and Studies
·' !. '.Pl··.··:'··i·; .. ~;1An.d:1,.;arz•r......_
... ·-~~-~-,·~-·---•:" --,~~-"··--__ .:---::·-'/·,,,.···:. .\.;.:; -:~··._~ :-·-_-,-,·. '-'--·~;:
Orange County Hazard Mitigation Plan Hazard Profiles; Capabilities Assessment; Mitigation
Strategy
State of California Multi-Hazard Mitigation Plan (2013) Hazard Profiles
Agency Urban Water Management Plans Hazard Profiles; Capabilities Assessment
Local General Plans Hazard Profiles; Capabilities Assessment; Local Plan
Integration
Local Municipal Codes Capabilities Assessment; Mitigation Strategy
FEMA Hazard Mitigation How-to Guides Plan Development; Plan Components
FEMA Local Mitigation Planning Handbook (March 2013) Plan Development; Local Plan Integration Methods
FEMA Mitigation Ideas: A Resource for Reducing Risk to Mitigation Strategy Development Natural Hazards (January 2013)
Orange County Water and Wastewater GIS Layers with Hazard Profiles; Risk/Vulnerability Assessments; Mitigation
Critical Infrastructure Facilities Strategy
Seismic Hazard Assessment, Orange County Seismic Hazard Profiles; Risk/Vulnerability Assessments; Mitigation Vulnerability, Mitigation and Recovery Planning Study Strategy (August 28, 2015)
Agency-specific Reliability Studies Hazard Profiles; Risk/Vulnerability Assessments; Mitigation
Strategy
Final I August 2019 2-8
SECTION TWO Planning Process Documentation
2.2.1 IDENTIFY/PROFILE HAZARDS
The Planning Team reviewed the hazards profiled in the 2012 Plan as well as a list of FEMA-identified
hazards to determine which hazards had the potential to impact the County and should be profiled as part
of the Plan update. Both the 2012 Plan and this Plan update include natural and human-caused hazards
that may threaten all or a portion of the County and individual MA. It was noted that some location-
specific hazards would not be applicable to every jurisdiction, but still warranted identification. Through
discussions of the hazards, including the probability, location, maximum probable extent, and potential
secondary impacts, a list of hazards was developed and prioritized. Content for each hazard profile is
provided in Section 3.0.
2.2.2 ASSESS VULNERABILITIES
Hazard profiling exposes the unique characteristics of individual hazards and begins the process of
determining which areas within the County are vulnerable to specific hazard events. The vulnerability
assessment included input from the Planning Team and a GIS overlaying method for hazard risk
assessments using infrastructure mapping completed in preparation of the Plan update. Using these
methodologies, water and wastewater infrastructure impacted by the profiled hazards were identified and
potential loss estimates were determined. Detailed information on the vulnerability assessments for each
hazard is provided in Section 3.0.
2.3 DEVELOP MITIGATION PLANS
The Plan update was prepared in accordance with DMA 2000 and FEMA's HMP guidance documents.
This plan provides an explicit strategy and blueprint for reducing the potential losses identified in the risk
assessment, based on existing authorities, policies, programs, and resources, and the MA ability to expand
on and improve these existing tools. Developing the mitigation plan involved identifying goals, assessing
existing capabilities, and identifying mitigation actions. This step of the planning process is detailed in
Section 4.0 and summarized below.
2.3.1 IDENTIFY GOALS
The Planning Team reviewed the goals identified in the 2012 Plan and determined that many of the MA
shared similar goals. As a result, one set of regional goals were developed as part of the Plan update. The
Mitigation Goals are presented in Section 4.0. For some MA, it was determined that additional goals
specific to their agency were still warranted and are included in the Jurisdiction Annexes, where
applicable.
2.3.2 DEVELOP CAPABILITIES ASSESSMENT
A capabilities assessment is a comprehensive review of all the various mitigation capabilities and tools
currently available to the MA to implement the mitigation actions that are prescribed in the Plan. The
Planning Team reviewed planning and regulatory, administrative and technical, financial, and education
and outreach capabilities to implement mitigation actions. Each MA reviewed capabilities information
from the 2012 Plan and working with their local teams, identified and updated the capabilities assessment
specific to their agency. The capabilities assessments for each MA are included in the Jurisdiction
Annexes.
Final J August 2019 2-9
SECTION TWO Planning Process Documentation
2.3.3 IDENTIFY MITIGATION ACTIONS
As part of the planning process, the Planning Team worked to identify and develop mitigation actions to
address the profiled hazards. The mitigation actions in the 2012 Plan were reviewed to determine
whether they had been achieved, were still relevant, or were no longer relevant due to changing
circumstances. Each MA considered the hazards applicable to their agency and identified and prioritized
mitigation actions. The mitigation actions for each MA are included in the Jurisdiction Annexes.
2.3.4 PLAN REVIEW AND REVISION
Once the draft Plan was completed, a public review period was provided from August 10, 2018 to
September 10, 2018 to allow public review and comments. Comments received on the draft Plan were
reviewed and the Plan was revised, as appropriate.
2.3.5 PLAN ADOPTION AND SUBMITTAL
This plan will be submitted and approved by FEMA and adopted by the MA approving bodies as the
official statement of their hazards. Copies of the resolutions will be provided in Appendix A.
2.3.6 PLAN MAINTENANCE
Plan maintenance procedures, found in Section 5, include the measures each MA will take to ensure the
Plan's continuous long-term implementation. The procedures also include the manner in which the Plan
will be regularly monitored, reported upon, evaluated, and updated to remain a current and meaningful
planning document.
Final I August 2019 2-10
SECTION THREE Risk Assessment
SECTION 3 RISK ASSESSMENT
Risk Assessment requires the collection and analysis of hazard-related data to enable local jurisdictions to
identify and prioritize appropriate mitigation actions that will reduce losses from potential hazards.
FEMA' s Local Hazard Mitigation Plan How-to Guide recommends four steps for conducting a risk
assessment:
1. Describe hazards that pose a threat to the planning area;
2. Identify community assets (for the purposes of this Plan this includes water and wastewater
infrastructure) in the planning area;
3. Analyze risks associated with the hazards, including describing the potential impacts and
estimating losses for each hazard; and
4. Summarize vulnerability to understand the most significant risks and vulnerabilities associated
with the identified hazards.
The risk assessment must result in an evaluation of potential impacts and overall vulnerability for each
participating jurisdiction to develop specific mitigation actions. The following identifies the hazards for
the entire planning area and notes if the hazard is applicable to all jurisdictions or is unique to specific
jurisdictions. Hazards applicable to all jurisdictions are described in this section and are not described
separately in the Jurisdictional Annexes. Hazards unique to a jurisdiction are further discussed in the
Jurisdictional Annexes.
3.1 HAZARD IDENTIFICATION AND PRIORITIZATION
3.1.1 Hazard Identification
Hazard identification is the process of identifying hazards that threaten an area including both natural and
man-made events. A natural event causes a hazard when it harms people or property. Such events would
include floods, earthquakes, tsunami, coastal storms, landslides, and wildfires that strike populated areas.
Human-caused hazard events are caused by human activity and include technological hazards and
terrorism. Technological hazards are generally accidental and/or have unintended consequences (for
example, an accidental hazardous materials release). Terrorism is defined by the Code of Federal
Regulations as " ... unlawful use of force and violence against persons or property to intimidate or coerce a
government, the civilian population, or any segment thereof, in furtherance of political or social
objectives." Natural hazards that have harmed the County in the past are likely to happen in the future;
consequently, the process of identifying hazards includes determining if the hazard has occurred
previously.
The Planning Team reviewed the list of FEMA-identified hazards, the 2012 Plan, as well as other relevant
information to determine the extent of hazards with potential to affect the planning area; refer to Table 2-
±, Existing Plans and Studies. A discussion of potential hazards during the first Planning Team meeting
resulted in the identification of the natural and human-induced hazards that pose a potential risk to all or a
portion of the County and individual Member Agency (MA). Table 3-1, Hazard Identification,
summarizes the Planning Team's discussion and identification of the hazards for inclusion in the Plan
update.
Final I August 2019 3-1
SECTION THREE
list of HazaRls Included ill
2112ftia?
Avalanche No
Climate Change No
Coastal Erosion No
Coastal Storm Yes
Contamination Yes
Dam Failure Yes
Disease/Pest Management No
Drought Yes
Earthquake Fault Rupture Yes
Expansive Soils Yes
Extreme Heat Yes
Flood Yes
Geological Hazards Yes
Hailstorm No
Hazardous Materials Yes
Final I August 2019
Risk Assessment
Table 3-1
Hazard Identification
111cludedin Discussion &nmmary 21t16flan?
Not applicable. Snowfall is not a typical occurrence in
No Orange County and there is no historical record of this
hazard in the region.
Yes Climate change is a phenomenon that could exacerbate
hazards. This hazard has been added to the Plan update.
Coastal erosion and storms occur within the coastal
Yes communities, which include development along the coast.
These hazards are combined in the Plan.
Yes Coastal erosion and storms occur within the coastal
communities. These hazards are combined in the Plan.
Water supplies are susceptible to contamination from
Yes human activities. In addition, salt water intrusion has
occurred previously due to the low water table.
Several dams and reservoirs are located throughout the
Yes County or in areas that could impact the County in the
event of a failure. Infrastructure is located within inundation
areas. This hazard includes dams and reservoirs.
No Not applicable. Disease/pest management is not a hazard
that impacts water/wastewater facilities and infrastructure.
Water supplies are dependent upon groundwater and
imported surface water, both of which are susceptible to
Yes drought. The County has experienced historical droughts,
including the most recent State-declared drought
emergency (2014-2017).
Alquist-Priolo fault zones occur within the County. The
Yes County has a long history of earthquakes, some resulting in
considerable damage. This topic has been combined with
Seismic Hazards (Ground Shaking and Liquefaction).
Expansive soils conditions occur within portions of the
Yes County and can be exacerbated by seismic ground
shaking. This topic is addressed under Geological
Hazards.
Extreme heat is not a hazard that typically affects the
No County, which is characterized by mild temperatures. This
hazard has been removed from the Plan update.
Portions of the County are located within floodplains and
Yes have experienced historic flooding. More localized flooding
also occurs during rainstorms.
The County is located in an area of geological hazards,
Yes including seismic activity. This topic has been combined
with Expansive Soils and Land Subsidence.
No Not applicable. Hailstorms rarely occur within the County
and there is no historical record of this hazard in the region.
Water supplies could be compromised from accidental or
Yes intentional release of hazardous materials. These topical
areas are addressed under Human-Caused Hazards.
3-2
SECTION THREE
List of Hazards lndmledifl
2112Pfan?
Human-Caused Hazards Yes
Hurricane No
Land Subsidence Yes
Landslide and Mudflow Yes
Lightning No
Liquefaction Yes
Power outage No
Sea Level Rise No
Seismic Hazards Yes
Severe Winter Storm No
Tornado Yes
Tsunami Yes
Volcano No
Wildfire Yes
Wind No
Windstorm Yes
Final I August 2019
Risk Assessment
Table 3-1 [continued]
Hazard Identification
Included in DiScussiom Summary 2116Plam?
Water supplies could be compromised from release of
hazardous materials or as a result of terrorist activities.
Yes Heightened security concerns have resulted in increased
measures to protect infrastructure systems. These topical
areas are addressed under Human-Caused Hazards.
No Not applicable.
Yes Land subsidence conditions occur within the County. This
topic is addressed under Geoloqical Hazards.
Areas of the County are susceptible to landslide and
Yes mudflow which can be exacerbated by other hazards
including seismic ground shaking, drought conditions, and
wildfires.
Not applicable. Although lightning sometimes occurs
No during storm events, it is limited within the region and there
is no historical record of this hazard in the reqion.
Liquefaction zones occur within the County. This topic has
Yes been combined with Earthquake Fault Rupture and Seismic
Hazards (Ground Shaking and Liquefaction).
Although typically associated with other hazards, power
Yes outages can directly impact water and wastewater systems
and has been added to the Plan update.
Sea level rise has been identified as a hazard affecting
Yes some of the coastal communities. This hazard has been
added to the Plan update.
The County has a long history of earthquakes, some
Yes resulting in considerable damage. This topic has been
combined with Earthquake Fault Rupture and addresses
Ground Shaking and Liquefaction.
Not applicable. Severe winter storms are not common in
No the County and there are no historical records of this
hazard in the reqion.
No Tornados are not a typical occurrence in the County. This
topic has been removed from the Plan.
Yes Portions of the Orange County coastline are identified as
tsunami inundation areas.
No Not applicable. There are no active volcanoes in the
County or surrounding area.
Portions of the County are located within very high and high
Yes fire hazard zones, which are adjacent to existing urban
development. Wildland and urban fires are combined
topics in the Plan.
Regular wind is not a typical occurrence and does not
No cause severe damage within the area. High winds/Santa
Ana winds are common throughout the County and are
addressed in the Plan (see Windstorm below).
Yes High Winds/Santa Ana Winds are a common occurrence in
the planning area and can impact power transmission lines.
3-3
SECTION THREE Risk Assessment
3.1.2 Hazard Prioritization
The Planning Team used a Microsoft Excel-based tool to prioritize the identified hazards by assigning
each hazard a ranking based on probability of occurrence and the potential impact. These rankings were
assigned based on a group discussion, knowledge of past occurrences, and familiarity with each MAs
vulnerabilities. Four criteria were used to establish priority:
• Probability (likelihood of occurrence)
• Location (size of potentially affected area)
• Maximum Probable Extent (intensity of damage)
• Secondary Impacts (severity of impacts to community)
A value from 1 to 4 was assigned for each criterion. The four criteria were then weighted based on the
Planning Team's opinion of each criterion's importance. Table 3-2, Hazard Rankings, presents the
results of the hazard rankings.
I,:·' '.: ·.i,':<'""' <!·,;.\··:;;, : • [: , ..
: ; "i :,:< .. ·':; ',.,;.,,' '· '.>: ;._.,<,, .l, ,:;,
Ff~;,~;:,,.' -, .. , ,,,,,_ '· '
i,· ·"''''';::.:;' ' ,.,, ;,," 1;j,<>1;< ~-·
·<~:'.:~:~h~/~'':i':l•i .. ··•••· ' '·, ;," ;
Power Outage
Wildfire
Seismic Hazards -Ground Shaking
Seismic Hazards -Liquefaction
High Winds/Santa Ana Winds
Drought
Dam/Reservoir Failure
Flood
Earthquake Fault Rupture
Landslide/Mudflow
Contamination
Human-Cause Hazards -Terrorism
Human-Caused Hazards -Hazardous Materials
Urban Fire
Geologic Hazards -Land Subsidence
Geologic Hazards -Expansive Soils
Tsunami
Table 3-2
Hazard Rankings
4 3 4 4 57.60
4 3 3 4 52.00
3 3 4 4 43.20
3 3 4 4 43.20
4 4 2 40.80
4 4 35.20
2 3 4 4 28.80
3 3 2 25.80
2 4 2 18.40
2 2 2 3 18.00
2 3 4 11.40
3 3 8.80
2 3 7.40
2 5.40
2 5.00
2 5.00
4.00
Scores are based on a scale from 1 to 4, where 4 is the highest score and 1 is the lowest. Refer to Table 3-3 for additional information.
The total score is based on an eauation that weiqhts cateqories by importance. Refer to Table 3-3 for additional information.
Final I August 2019
High
High
High
High
Medium
Medium
Medium
Medium
Medium
Medium
Low
Low
Low
Low
Low
Low
Low
3-4
SECTION THREE Risk Assessment
Table 3-3, Hazard Ranking Methodology, provides additional detail regarding how the probability,
affected area, and impact categories are weighted and how the total score is calculated for the hazard
rankings.
Table 3-3
Hazard Ranking Methodology ,......, (DlportaKe 2.1 SecoHdaty flllpads I Importance 1.5
Based on estimated likelihood of occurrence from Based on estimated secondary impacts to community at large. historical data.
Probability Score Impact Score
Unlikely (less than 1 % probability in next Negligible -no loss of function, downtime,
100 years or has a recurrence interval of 1 and/or evacuations 1
greater than every 100 years)
Somewhat Likely (between 1 % and 10% Limited -minimal loss of function, downtime,
probability in next year or has a 2 and/or evacuations 2
recurrence interval of 11 to 100 years)
Likely (between 10% and 100% Moderate -some loss of function, downtime,
probability in next year or has a 3 and/or evacuations 3
recurrence interval of 10 years or less)
Highly Likely (near 100% probability in 4 High -major loss of function, downtime, 4 next year or happens every year) and/or evacuations
' ;.:_w:'rieiii< ···· ; ·~:·.· :<.:+···. : :;•. '· ' ,· ' "· ''
:.: ... 1i11ttt u. Teeat5-e=PJGI l.,x....,,lllteiE, ;····:·'; .... '\ ..
' ·. •,'
Based on size of geographical area of community Probability= (Probability Score x Importance) affected by hazard.
Affected Area Score Impact = (Affected Area + Primary Impact + Secondary Impacts),
where:
Isolated 1 Affected Area= Affected Area Score x Importance
Small 2 Primary Impact = Primary Impact Score x Importance
Medium 3 Secondary Impacts = Secondary Impacts Score x Importance
Large 4
~ ...... ....... u Hazard: ..... Considelration ....... ,
Based on percentage of damage to typical facility in Total Score Range Distribution Hazard
:;ommunity. Level
Impact Score 0.0 20.0 0 Low
Negligible -less than 10% damage 1 20.1 42.0 6 Medium
Limited -between 10% and 25% 2 42.1 64.0 3 High damage
Critical -between 25% and 50% damage 3
Catastrophic -more than 50% damage 4
The probability of each hazard is determined by assigning a level, from unlikely to highly likely, based on the likelihood of occurrence from
historical data. The total impact value includes the affected area, primary impact, and secondary impact levels of each hazard. Each level's
score is reflected in the matrix. The total score for each hazard is the probability score multiplied by its importance factor times the sum of
the impact level scores multiplied by their importance factors. Based on this total score, the hazards are separated into three categories
based on the hazard level they pose to the communities: Hiqh, Medium, and Low.
Final I August 2019 3-5
SECTION THREE Risk Assessment
It should be noted that climate change and coastal storm/erosion were not prioritized for the planning
area; refer to the Jurisdiction Annexes for an assessment of each of the hazards specific to the individual
jurisdiction. Although climate change is identified as a hazard in the Plan update, there was not
consensus on how it impacts the individual jurisdictions. Similarly, coastal storm/erosion was considered
distinct to specific MAs and potentially exacerbated by climate change. Regardless of the prioritization
(low, medium, or high), it was determined by the Planning Team that all the hazards identified in Table 3-
1 would be profiled. Due to the vast geography and hazards that impact the various MAs, it was
recognized by the Planning Team that some hazards that ranked low overall, may be a high priority
depending upon the jurisdiction.
3.2 HAZARD PROFILES
This section contains profiles for the hazards identified in Table 3-1. Due to the nature of the hazards,
some hazards were combined for purposes of the profiles as noted in Table 3-1. Information was
obtained from various Federal, State and local sources, as well as the Planning Team. A detailed list of
References is provided in Section 6.0.
The service areas for each of the MAs participating in the Plan update do not always align with
incorporated City or unincorporated County boundaries. In many cases, a MA may serve multiple cities
and/or portions of cities/unincorporated areas. For purposes of this Plan update, the planning area refers
to Orange County, since the MAs provide services and infrastructure throughout most of the County.
Because much of the available hazard data is provided by jurisdictional boundary (County or City), it is
not always possible to obtain or delineate data specific to the MA jurisdictional (service) boundary. The
Jurisdictional Annexes detail the hazards, risk assessments, and mitigation strategies specific to each
jurisdiction.
Each hazard profile addresses the following:
• Description (Nature) ofthe Hazard: Describes the hazard and its characteristics.
• History/Past Occurrences: Provides a history of the hazard and identifies previous occurrences.
Where an occurrence is specific to a MA, this information is provided.
• Location/Geographic Extent: Describes the location (geographic) area affected by the hazard. If
the hazard affects the entire planning area, it is noted. For geographically specific hazards, the
specific MAs affected by the hazard are identified and discussed further in the Jurisdictional
Annexes.
• Magnitude/Severity: Describes the extent (magnitude or severity) of each hazard. If a hazard has
a uniform extent for all the MAs, it is noted. For geographically specific hazards, mapping is
provided that illustrates the extent of the hazard for the entire planning area. Mapping for
applicable hazards specific to a MA are provided in the Jurisdictional Annexes.
• Probability of Future Occurrences: Provides a discussion of the probability of future
occurrences of the hazard based on the history of past occurrence, location, and severity. If the
likelihood of occurrence is the same for all jurisdictions or varies amongst the jurisdictions, it is
noted.
Final I August 2019 3-6
SECTION THREE Risk Assessment
3.2.1 Climate Change
3.2.1.1 Description (Nature) of the Hazard
According to NASA's Global Climate Change website, the mean global temperature has increased 1.8
degrees Fahrenheit since 1880, and 17 of the 18 warmest years on record have occurred since 2001. 1 The
scientific consensus is that these changes are the result of human activity increasing the levels of carbon
dioxide and other greenhouse gases in the atmosphere, and that they will intensify. The
Intergovernmental Panel on Climate Change forecasts temperatures to rise an additional 2.5 to 10 degrees
over the next century. Such drastic changes to the earth's climate will have significant consequences
around the globe. Long-term effects include rising sea levels due to melting ice, changes in precipitation
patterns, heat waves, and more frequent and intense storms.
Based on local data from the National Oceanic and Atmospheric Administration (NOAA)2 , Orange
County can expect to see its daily maximum temperature increase from a current annual average of 73
degrees to 78 degrees by 2100 under a low-emission scenario and 82 degrees under a high-emission
scenario. The County currently experiences an average of 4.5 days a year where temperatures reach 95
degrees; that is projected to increase to as many as 31 days a year. Under both emission scenarios, the
County is likely to see a 43 to 44 percent increase in the amount of rain that falls during the winter by the
latter half of the century.
Climate Change presents a number of challenges for Orange County. According to the 2014 National
Climate Assessment Report, as is common in coastal areas, many roads and bridges, high-priced homes,
and wastewater systems are located in low-lying areas near the ocean. Increases in storm water runoff
have the potential to overwhelm the capacity of wastewater and drainage systems, flood control channels,
and pump stations. Climate change may endanger vulnerable coastal ecosystems and wildlife habitats or
degrade water quality at beaches. In addition, because the region relies extensively on imported water,
climate effects beyond Orange County, particularly in Northern California and the Colorado River
watershed, will have consequences for the County's water supply.
Climate change may influence many of the other hazards addressed in this plan. As the oceans rise, more
areas may be subject to coastal flooding and tsunami risk, coastal erosion may increase, and aquifers may
be contaminated by additional salt water intrusion. Seasonal changes in rainfall may result in greater risk
of flooding, dam failure, drought, wildfire, land subsidence, expansive soils, and landslides and
mudflows. Extreme heat can reduce soil moisture, further exacerbating such hazards as drought, wildfire,
and expansive soils.
This profile focuses on the hazard of coastal flooding as a result of sea-level rise, while any interactions
between climate change and other hazards will be primarily addressed in those hazard profiles. In
contrast to the Atlantic and Gulf coasts, where coastal flooding is mainly associated with major storms,
flooding along the Pacific Coast is the result of a number of more subtle factors, including tidal cycles;
the El Nino climate pattern; distant, wind-generated ocean swells; local storms; and the time of year. Sea-
level rise means that more areas will be more susceptible to the complex interactions between these
processes and more frequent flooding.
1 NASA (2018, March 19). Global Climate Change Vital Signs of the Planet. https://climate.nasa.gov/. Accessed
March 2018.
2 U.S. Climate Resilience Toolkit, The Climate Explorer. https://toolkit.climate.gov/climate-explorer2/. Accessed
March 2018.
Final I August 2019 3-7
SECTION THREE Risk Assessment
3.2.1.2 History/Past Occurrences
NOAA offers an online Climate Explorer toolkit3 that shows climate projections and observed historical
trends by county. The data shows that, from 1949 to 2009, the daily maximum temperature in Orange
County has been gradually rising at a rate of about 0.02 degrees Fahrenheit per year. This is expected to
accelerate through the end of the century, although the degree depends on the success of efforts to limit
global carbon emissions.
NASA reports that the global average sea level has risen almost 7 inches in the last 100 years. Rising sea
levels have been observed in Orange County, as well. Measurements taken at Newport Beach since 1955
show that the sea level there has risen an average of 2.22 millimeters, or 0.09 inches, per year.4 This is
also expected to accelerate as more ice melts due to rising global temperatures.
King tides have flooded Orange County coastal communities, including Seal Beach, Huntington Beach,
Balboa Peninsula and Balboa Island in Newport Beach, and Sunset Beach in the past.5 In the last 10
years, the National Centers for Environmental Information (NCEI) Storm Events Database reports four
coastal flooding incidents affecting Orange County: in October and November 2015, and May and
October 2017. It is difficult to say how higher sea levels may have affected the severity of these events.
The independent organization Climate Central estimates that La Jolla, California, located 46 miles from
Huntington Beach, experienced 60 days of coastal flooding between 2005 and 2014, based on observed
impacts such as flooded roads. Of those events, only four would have occurred without climate-linked
sea-level rise.6
3.2.1.3 Location/Geographic Extent
Sea-level rise presents a risk for all coastal communities with low-lying areas. In Orange County,
Huntington Beach is particularly vulnerable.
A 2017 report by the Union of Concerned Scientists, "When Rising Seas Hit Home," includes a mapping
tool that shows what coastal areas will experience flooding at least 26 times a year under various sea-level
rise scenarios. Under a moderate scenario of a 4-foot rise, the area of north Orange County roughly
bounded by the Santa Ana River and State Route 22 will see 14 percent of its land chronically inundated
by 2100, even with existing levees. With a rise of 6 feet, 24 percent of the land will be chronically
inundated. Affected areas include neighborhoods in Seal Beach, Huntington Beach, and Newport Beach.
NOAA offers another mapping tool to visualize areas vulnerable to flooding due to climate change. Its
Sea Level Rise Viewer projects that, with a 1-foot rise in sea levels, there will be flooding through many
parts of southeastern Huntington Beach, including neighborhoods between the Talbert Chanel and
Huntington Beach Channel. A 2-foot rise will also start to affect parts of Sunset Beach and Balboa Island
in Newport Beach, as well as less developed areas of Upper Newport Bay, Bolsa Chica Ecological
Reserve.
3 Available at https://toolkit.climate.gov/climate-explorer2/
4 NOAA. Tides and Currents. https://tidesandcurrents.noaa.gov/sltrends/sltrends _station.shtml?stnid=9410580.
Accessed March 2018.
5 The OCR. January 10, 2017. Orange County Beach Cities Bracing for 7-foot King Tides; Flooding Possible.
https://www.ocregister.com/2017/01/1 Of orange-county-beach-cities-bracing-for-7-foot-king-tides-flooding-possible/. Accessed
March 2018.
6 Climate Central, Surging Seas Risk Finder. https://riskfinder.climatecentral.org/place/huntington-beach.ca.us?
comparisonType=place&forecastName=Single-year&forecastType=NOAA2017 _int_p50&level=3&unit=ft. Accessed March
2018.
Final I August 2019 3-8
SECTION THREE Risk Assessment
3.2.1.4 Magnitude/Severity
Sea level is measured by local tide gauges and satellite. Sea-level rise describes projected changes in
those measurements based on different climate models. NOAA's Sea Level Rise Viewer projects that the
sea level at Newport Bay will rise by at least 0.75 feet and as much as 2.72 feet by 2050, based on
different global scenarios. By 2100, the level may rise by as much as 10.14 feet under the most extreme
scenario.
3.2.1.5 Probability of Future Occurrences
FEMA' s Flood Insurance Rate Map (FIRM) panels, which show areas that are subject to a 1 percent
annual chance of flooding, reflect only current risk; they do not attempt to make projections based on
anticipated changes due to climate change and sea-level rise.
Climate Central's Surging Sea Risk Finder attempts to estimate the probability that coastal floods will
reach elevations above the local high tide line. The tool does not have estimates for every tide gauge, and
estimates for Orange County are based on data from the gauge at Los Angeles' Outer Harbor. It shows
that, while there is currently less than a 1 percent chance of coastal flooding reaching areas three feet
above the tide line in any given year, those chances increased to 6 percent annually by 2040 under a
medium sea-level rise scenario. By 2070, these areas will be flooding every year. Under an extreme
scenario, annual flooding will happen as soon as 2040.
3.2.2 Coastal Storms/Erosion
3.2.2.1 Nature of Hazard
Erosion is a naturally occurring phenomenon all along California's coastline. Erosion can be severe
during winter storms, which are often accompanied by high surf, particularly during El Nino events.
Rising sea levels caused by climate change will increase coastal erosion by exacerbating the impact of
high tides and waves. Climate change is also expected to increase the frequency and severity of storms.
As a result, even areas that have not experienced significant erosion in the past may be at risk in the
future. (Effects of climate change are discussed in detail in Section 3 .1.1 ).
Erosion can also be affected by manmade structures that impede the deposit of new sediment at beaches;
these include inland dams, channelized rivers, harbors, jetties, and seawalls/revetments. 7 This has been
the case in Orange County, where the channelization of the Santa Ana River has reduced the amount of
sediment reaching the coast, while the construction of jetties at Anaheim Bay and breakwaters at Long
Beach have changed deposit patterns. 8 This led to the formation of several chronic erosion hotspots along
the County's coastline. In some cases, long-term beach replenishment efforts and management plans
have been able to counteract or reverse these trends.
In addition to the gradual narrowing of sandy beaches, storms and erosion can damage steep coastal bluffs
and cliffs. Landforms that appear to have been stable for years may retreat several feet in just a few
hours. In either case, erosion can cause considerable damage to coastal infrastructure and property. As
7 Coastal Erosion -Needs for Beach Nourishment. http://www.dbw.ca.gov/csmw/PDF/Results_From_CSMW _
Taskl.pdf
8 California Beach Restoration Study. January 2002. https://www.parks.ca.gov/pages/28702/files/cbrs_ch6_
effectiveness. pdf
Final I August 2019 3-9
SECTION THREE Risk Assessment
Orange County's beaches are centers for recreation and tourism, loss of land has economic consequences,
as well.
3.2.2.2 History/Past Occurrences
Problems with chronic erosion in Orange County have been recognized since at least 1945, when beach
nourishment operations were undertaken to shore up the eroding Surfside-Sunset shoreline.9 A 2006 U.S.
Geological Survey (USGS) assessment of the entire California coast found that, between Los Angeles
Harbor and Dana Point, the shoreline had receded since the early 1970s for 35 percent of the 29-miles
coastline. Beach nourishment projects prevented further observable erosion during this period.
California typically experiences the most erosion during significant El Nino events. The three strongest
El Nino events on record were during the winters of 1982-1983, 1997-1998, and 2015-2016. Historic
erosion was reported all along the West Coast in 2015-2016, according to the USGS.10 While the winter
storms brought extreme wave action to California's shores, they featured surprisingly little rainfall. With
California in the midst of a major drought, less sediment was washed to the ocean to replenish beaches.
Portions of beaches in San Clemente and Laguna Beach were temporarily closed to the public due to
hazardous conditions. 11
3.2.2.3 Location/Geographic Extent
Orange County's coastline includes sand and cobble beaches, rocky cliffs and coastal bluffs, and intertidal
areas. In general, beach erosion is more of an issue along the County's northern coast, while bluff retreat
is a greater concern along the southern portion.
Beginning in 1964, the Orange County Erosion Control Project targeted Surfside-Sunset and West
Newport Beach as locations in need of restoration. The U.S. Army Corps of Engineers spearheaded
efforts to import sand and installing retention devices in these areas.
The 2006 USGS study found that West Newport Beach had the largest measurable erosion rate in Orange
County between the early 1970s and 1998.
As part of the Coastal Storm Modeling System (CoSMoS), data available from the USGS shows the
projected location of the California shoreline under various scenarios of sea-level rise. The Coastal Storm
Modeling System (CoSMoS-COAST) shows that with a 3.3-foot rise in sea levels, Huntington State
Beach will see the greatest erosion, followed by parts of Huntington City Beach, West Newport Beach,
Surfside, and Bolsa Chica State Beach.
3.2.2.4 Magnitude/Severity
Erosion is usually described in terms of how much the beach width deceases per year. The 2006 USGS
study, for example, found that erosion at West Newport Beach was at a rate of -2.2 meters per year.
9 California Beach Restoration Study. January 2002. https://www.parks.ca.gov/pages/28702/files/cbrs_ch6_
effectiveness. pdf.
10 USGS. February 14, 2017. Severe West Coast Erosion During 2015-16 El Nino. https://www.usgs.gov/news/
severe-west-coast-erosion-during-2015-16-el-ni-o.
11 The Orange County Register. February 9, 2016. Our Eroding Coastline: Recent storms are reshaping beaches, and
some are getting tougher to visit. https://www.ocregister.com/2016/02/09/our-eroding-coastline-recent-storms-are-reshaping-
beaches-and-some-are-getting-tougher-to-visit/. Accessed August 2017.
Final I August 2019 3-10
SECTION THREE Risk Assessment
Overall, the shoreline of Los Angeles Harbor and Dana Point grew by an average of 0.5 meters per year,
the highest rate in all of California, due largely to beach nourishment projects. Among those sections that
did experience erosion, it happened at an average rate of -0.5 meters per year.
The volume of sand used to fight erosion can also indicate the magnitude of the problem. For example,
from 1945 to 2009, more than 20 million cubic yards of sediment has been added to Surfside-Sunset
Beach.12
3.2.2.5 Probability of Future Occurrences
Climate change all but ensures that the entire Orange County coast will experience some degree of
erosion through the end of the century. The amount will depend on how much sea levels rise, which is
contingent on global efforts to curb greenhouse gas emissions. An online mapping tool produced by Our
Coast Our Future, a collaborative effort of 15 organizations including the USGS and California Coastal
Commission, using CoSMoS data projects that very few sections of the County's shoreline will maintain
their current position assuming a 3.3-foot rise in sea level, even with the continuation of current beach
nourishment efforts.
A new study released in 2017 using CoSMoS data found that, without human intervention, 31 to 67
percent of Southern California beaches may be completely eroded by 2100 if sea levels rise by 1 to 2
meters.13
3.2.3 Contamination/Salt Water Intrusion
3.2.3.1 Description (Nature) of the Hazard
GROUNDWATER CONTAMINATION
Groundwater contamination occurs when pollutants are released to the ground, navigate through the soil,
and ultimately end up in the groundwater. Human activity is almost always the underlying cause of
groundwater contamination. In areas where population density is high and human use of land is intensive,
groundwater is especially vulnerable. Virtually any activity whereby chemicals or wastes may be
released to the environment, either intentionally or accidentally, has the potential to pollute groundwater.
SALT WATER INTRUSION
When fresh water is withdrawn from aquifers at a faster rate than it is replenished, a drawdown of the
water table occurs with a resulting decrease in the overall hydrostatic pressure. When this happens near a
coastal ocean area, salt water from the ocean can intrude into the fresh water aquifer. The result is that
fresh water supplies become contaminated with salt water.
12 U.S. Army Corps of Engineers. 2012. Orange County Coastal Regional Sediment Management Plan Draft Report.
http://www.dbw.ca.gov/csmw/pdf/OCCRSMP _DraftReport.pdf.
13 USGS. March 27, 2017. Disappearing Beaches: Modeling Shoreline Chane in Southern California. https://www.
usgs.gov/news/disappearing-beaches-modeling-shoreline-change-southern-california.
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3.2.3.2 History/Past Occurrences
GROUNDWATER CONTAMINATION
Over the last several decades, Orange County's North Basin has experienced industrial solvent spills and
leaks from manufacturing, metals processing businesses, and dry-cleaning facilities. As a result, a
contamination plume several miles long and over a mile wide currently exists under the cities of
Fullerton, Anaheim, and Placentia. The Orange County groundwater basin is a source of drinking water
for the region, providing most of the water used in 22 cities. The contamination plume has already taken
five wells off line, including three of Fullerton's 12 total wells. Those wells draw water from shallower
sources closer to the surface and consequently are closer to the pollution. Under the supervision of the
United States Environmental Protection Agency (USEP A), a remedial investigation and feasibility study
will be conducted to address the extent of contamination and to develop an initial cleanup plan.
Salt Water Intrusion
In Orange County, by 1956, years of heavy pumping to sustain the region's agricultural economy had
lowered the water table by 15-feet below sea level and saltwater from the Pacific Ocean had encroached
as far as five miles inland. The area of intrusion is primarily across a four-mile front between the cities of
Newport Beach and Huntington Beach known as the Talbert Gap. The mouth of an alluvial fan formed
millions of years ago by the Santa Ana River; the Talbert Gap has since been buried along the coast by
several hundred feet of clay. In 1976 the Water Factory 21 Direct Injection Project, operated by OCWD,
began injecting highly treated recycled water into the aquifer to prevent salt water intrusion, while
augmenting the potable groundwater supply. This system was shutdown to make way for the
Groundwater Replenishment System (GWRS) Project which began operation in 2008. The GWRS
provides highly treated water for injection into the seawater barrier system to prevent seawater intrusion
into the groundwater basin managed by OCWD. As of March 21, 2018, approximately 248 billion
gallons of water have been successfully treated and injected into the seawater barrier system.
3.2.3.3 Location /Geographic Extent
Groundwater contamination may occur County wide by means of intentional or accidental spillage to
groundwater.
Conversely, the coastal area of the Basin is vulnerable to seawater intrusion due to geologic features and
increased pumping from inland municipal wells to meet consumer demands. The susceptible locations in
the Basin are the Talbert, Bolsa, Sunset, and Alamitos Gaps.
3.2.3.4 Magnitude/Severity
The 197 4 Safe Drinking Water Act require the USEP A set standards for contaminants in drinking water
that may pose health risks to humans. The USEP A standard for lifetime exposures in drinking water, the
maximum contaminant level (MCL), is the highest amount of a contaminant allowed in drinking water
supplied by municipal water systems.14 In Orange County over 700 monitoring wells assess water quality
conditions.15 Thus, it is unlikely that human consumption of contaminated groundwater will occur. A
14 USEP A. National Primary Drinking Water Regulations. https://www.epa.gov/ground-water-and-drinking-water/
national-primary-drinking-water-regulations.
15 Orange County Water District Groundwater Management Plan. 2015. https://www.ocwd.com/media/3622/
groundwatermanagementplan2015update _ 20150624.pdf.
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SECTION THREE Risk Assessment
large environmental spill could result in contamination of groundwater; however, the extent and the
severity cannot be predicted. Based on historical occurrences, a contamination in the groundwater basin
could extend several miles and result in water wells being unavailable.
Massive seawater intrusion has been prevented in Orange County by the OCWD basin management
programs. However, the threat of saltwater intrusion along the coast is still present. To prevent further
intrusion and to provide basin management flexibility, OCWD operates a hydraulic barrier system. A
series of 23 multi-point injection wells four miles inland delivers fresh water into the underground
aquifers to form a water mound, blocking further passage of seawater. Continued injection of recycled
water into the aquifer is essential to keep saltwater from intruding into the groundwater table and
contaminating a major source of the county's potable water. OCWD maintains the Coastal Aquifer
Mergence Zones and Chloride Concentration map, which indicates a 250 mg/L Chloride Concentration
Contour. This contour is used to indicate the approximate leading edge of seawater intrusion. OCWD
monitors the movement of the chloride contour to provide an indication of whether seawater intrusion is
worsening or improving in a given area.
3.2.3.5 Probability of Future Occurrences
Due to the amount and types of urban development that occur within the County, and the transportation
systems that allow for the movement of hazardous materials through the County and greater region, future
groundwater contamination is likely. However, as a result of groundwater monitoring and protection
systems, human consumption of contaminated groundwater is unlikely.
Due to the successful operation of the OCWD basin management programs, the probability of saltwater
intrusion to occur in the future is unlikely.
3.2.4 Dam/Reservoir Failure
3.2.4.1 Description (Nature) of the Hazard
Dam failures can result from several natural or human caused threats such as earthquakes, erosion of the
face or foundation, improper silting, rapidly rising flood waters, malicious events, and structural/design
flaws. Seismic activity can also compromise dam regulating structures, resulting in catastrophic flooding.
A dam failure can cause loss of life, damage to property, the displacement of persons, and other ensuing
hazards residing in the inundation path. Damage to electric generating facilities and transmission lines
could also impact life support systems in communities outside the immediate hazard areas.
In the event of a major dam failure, mutual aid from all levels of government would be required for an
extended period. Recovery efforts would include the removal of debris, clearing roadways, demolishing
unsafe structures, assistance in reestablishing public services, and providing continued care and welfare
for the affected population.
There are 33 dams in Orange County with ownership ranging from the Federal government to
homeowners' associations. These dams hold billions of gallons of water in reservoirs. The major
reservoirs are designed to protect Southern California from flood waters and to store domestic and
recycled water.
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SECTION THREE Risk Assessment
In addition to reservoirs with dams in Orange County, there are many water storage tanks that are
potentially susceptible to failure or damage by natural or manmade events. These water tanks contain
millions of gallons of water each and provide an important source of water storage. Their capacity is
large enough to cause substantial damage down slope from a tank should one fail. Correspondingly, the
history of failure of water storage tanks is considered.
Because dam failure can have severe consequences, FEMA and Cal OES require all dam owners to
develop Emergency Action Plans (EAP) for warning, evacuation, and post-flood actions. Although there
has been extensive coordination with County officials in the development of a County Response Plan, the
responsibility for developing potential flood inundation maps and facilitation of emergency response is
the responsibility of the dam owner.
3.2.4.2 History/Past Occurrences
Orange County has never experienced a major dam failure, but there have been two deadly incidents
involving dams built to supply water for the City of Los Angeles. In addition, the failure of a water tank
caused considerable damage within the City of Westminster in 1998. These three disasters are detailed
below.
ST. FRANCIS DAM, DISASTER OF 1928
In Los Angeles, the failure of the St. Francis Dam, and the resulting loss of over 500 lives was a scandal
that resulted in the almost complete destruction of the reputation of its builder, William Mulholland. It
was he who proposed, designed, and supervised the construction of the Los Angeles Aqueduct, which
brought water from the Owens Valley to the city. The St. Francis Dam, built in 1926, was 180 feet high
and 600 feet long. It was located near the City of Saugus in San Francisquito Canyon.
The dam failed on March 12, 1928 three minutes before midnight. Its waters swept through the Santa
Clara Valley toward the Pacific Ocean about 54 miles away. The valley was devastated before the water
finally made its way into the ocean between Oxnard and Ventura. At its peak the wall of water was said
to be 78 feet high. At the time the water flowed through Santa Paula, 42 miles south of the dam, the
water was estimated to be 25 feet deep. Almost everything in its path was destroyed: livestock,
structures, railways, bridges, and orchards. In the end Ventura County lay below 70 feet of mud and
damage estimates topped $20 million.
BALDWIN HILLS DAM, DISASTER OF 1963
The Baldwin Hills Dam collapse sent a 50-foot wall of water down Los Angeles' Cloverdale Avenue on
December 14, 1963. Five people were killed. Sixty-five hillside houses were ripped apart, and 210
homes and apartments were damaged. The flood swept northward in a V-shaped path roughly bounded
by La Brea Avenue, Jefferson Boulevard, and La Cienega Boulevard.
The earthen dam that created a 19-acre reservoir to supply drinking water to West Los Angeles residents
ruptured at 3:38 p.m. A pencil thin crack widened to a 75-foot gash allowing 292 million gallons to surge
out in 77 minutes. The cascade caused an unexpected ripple effect that is still being felt in Los Angeles
and beyond. It prompted the end of urban-area earthen dams as a major element of water storage systems,
and a tightening of the Division of Safety of Dams control over reservoirs throughout the state.
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SECTION THREE Risk Assessment
WESTMINSTER WATER TANK FAILURE, DISASTER OF 1998
In September of 1998, a 5-million-gallon municipal water storage tank in the City of Westminster
ruptured because of corrosion and construction defects. There was no loss of life, but damage was
extensive. The flow of water from the 32-year-old tank destroyed most of the storage facility as well as
several private residences. Additionally, there were approximately 30 more homes inundated with water
and silt. Through the Public Works Mutual Aid Agreement, the Orange County Public Works
Department assisted the City of Westminster in the cleanup and temporary repair of the streets.
City employees, the Orange County Fire Authority, neighboring fire services, and the Red Cross were on-
site for days assessing the damage and assisting residents. Water storage for the City was non-existent
following this event while the other 5-million-gallon tank of similar age and construction was removed
from service as a precautionary measure.
A new reservoir facility came on-line in March 2003, consisting of two 8-million-gallon water storage
tanks, a 17-million-gallon-per-day booster station, and a new groundwater well with a capacity of 3,000
gallons per minute. All new construction has passed rigorous inspections and has obtained the required
permits from the California Department of Public Health.
3.2.4.3 Location/Geographic Extent
The following is a list of the larger reservoirs and dams in Orange County and their owners/operators:
Name of Facility
Santiago Dam/Reservoir (Irvine Lake)
Villa Park Dam
Sulphur Creek Dam
Peters Canyon Dam
Walnut Canyon Dam/Reservoir
San Joaquin Dam/Reservoir
Sand Canyon Dam/Reservoir
Rattlesnake Canyon Dam/Reservoir
Big Canyon Dam/Reservoir
Lake Mission Viejo
El Toro R-6 Dam/Reservoir
El Toro Reservoir/Rossmoor #1 Dam
Diemer Filtration Plant
Palisades Bradt Dam/Reservoir
Portola Dam/Reservoir
Syphon Canyon Dam/Reservoir
Trabuco Dam & Reservoir
Dove Canyon Dam
Upper Oso Dam/Reservoir
Upper Chiquita Dam/Reservoir
BreaDam
Fullerton Dam
Carbon Canyon Dam
Prado Dam
Final I August 2019
Owner/Operator
Serrano Water District/Irvine Ranch Water District
County of Orange
County of Orange
County of Orange
City of Anaheim
Irvine Ranch Water District
Irvine Ranch Water District
Irvine Ranch Water District
City of Newport Beach
Lake Mission Viejo Association
El Toro Water District
El Toro Water District
Metropolitan Water District
South Coast Water District
Santa Margarita Water District
The Irvine Company
Trabuco Canyon Water District
Dove Canyon Master Association/
Trabuco Canyon Water District
Santa Margarita Water District
Santa Margarita Water District
U.S. Army Corps of Engineers
U.S. Army Corps of Engineers
U.S. Army Corps of Engineers
U.S. Army Corps of Engineers
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SECTION THREE Risk Assessment
As mentioned above, the responsibility for developing maps showing areas that would be inundated in the
event of a failure is the responsibility of the dam's owner. Dams and reservoirs impacting the planning
area are summarized below:
Big Canyon Reservoir is a 600-acre foot potable water storage facility constructed in 1959 and owned by
the City of Newport Beach. It is in the San Joaquin Hills overlooking Newport Bay. Big Canyon
Reservoir is retained on three sides by a homogenous earth filled embankment dam, while the east side
was formed by a slope cut. At its maximum section the dam embankment is 65 feet high. The spillway is
an ungated concrete lined overflow structure located on the west side of the reservoir. The bottom of the
reservoir and the cut slopes are lined with minimum 5-foot-thick clay blanket, and the entire inside
surface, including the embankments and cut slopes, is overlain with a three-inch-thick porous asphalt
pavement. The reservoir is covered with a reinforced polypropylene weight-tensioned floating cover that
was installed in 2004.
Dove Canyon Dam is an earth-filled dam completed in 1990. The dam is in the Dove Canyon residential
community within the City of Rancho Santa Margarita, Orange County. The dam is owned by the Dove
Canyon Master Association (DCMA). DCMA owns and operates recreational facilities situated
immediately downstream of the dam crest on compacted backfill. The recreational facilities were
included in the construction documents for the Dam and approved by the State Division of Safety of
Dams. The impounded reservoir is located on land owned by Trabuco Canyon Water District (TCWD)
and is used to store up to about 415 acre-feet of runoff. TCWD and DCMA have an agreement to operate
and maintain the dam and reservoir. TCWD utilizes storage in the reservoir to supplement its recycled
water demands for landscape irrigation. The impounded water can be stored to an elevation of 1090 feet,
approximately 11 feet below the top of the dam crest's elevation of 1101 feet, MSL.
El Toro Reservoir/Rossmoor #1 Dam is an embankment type dam owned and operated by ETWD. The
reservoir is located in the City of Mission Viejo. The impounded reservoir has a storage capacity of 275
million gallons (850 acre-feet) with a surface area of approximately 20.6 acres. The bottom and internal
slopes of the reservoir are lined, and the reservoir surface has a floating cover. There is no surface water
influent to the reservoir. The reservoir includes an emergency spillway and drainage facilities. Storage
capacity in the El Toro Reservoir is owned through a regional partnership between ETWD, Santa
Margarita Water District and Moulton Niguel Water District.
Rossmoor #1 dam is an embankment type dam, with a height of 36 feet and a length of approximately
305 feet. The dam is located in the City of Laguna Woods. The impounded Holding Pond is used to
provide emergency storage of secondary effluent from the ETWD Water Recycling Plant and has a
storage capacity of 14 million gallons (43 acre-feet). The reservoir includes an emergency spillway and
drainage facilities.
Palisades Bradt Reservoir provides up to 48 million gallons of potable water storage with a 146-foot-
high, zoned, earthen embankment dam constructed in 1963. The bottom and internal slopes of the
reservoir are lined and the reservoir surface has a floating cover. The dam has a low-level outlet, an
emergency outlet, and an emergency spillway. The upstream watershed that contributes inflow to the
reservoir has an area of 19 acres.
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SECTION THREE Risk Assessment
Peters Canyon Dam is an earth-filled structure owned by the County of Orange and has a capacity of
626 acre-feet at the spillway pipe elevation of 537 feet MSL. Water storage varies from 200 acre-feet to
600 acre-feet depending on seasonal rain amounts. Alerting would come primarily from the Park Ranger
at Peters Canyon Regional Park who would notify the Sheriff Department, Control One of dam failure or
possible dam failure.
Prado Dam is owned and operated by the Army Corps of Engineers and provides flood control and water
conservation storage for Orange, Riverside and San Bernardino counties. Prado Dam is a major
component of the Santa Ana Mainstem Project, which extends from the upper canyon in the San
Bernardino Mountains downstream to the Pacific Ocean at Newport Beach -some 75 miles along the
Santa Ana River. The entire system is designed to provide various levels of flood protection ranging from
100 to 190 years for areas most susceptible to damage from flooding.
Prado Dam collects upstream water releases from storage facilities and runoff from uncontrolled drainage
areas. It primarily benefits Orange County by reducing the potential for flood-induced damage and by
providing water conservation storage. Prado Dam has been undergoing major improvements including
raising the embankment and spillway; increasing the maximum discharge capacity, constructing new
levees and dikes, relocating and protecting utility lines, increasing reservoir area and increasing
impoundment.
Portola Dam is located near the northern end of Canada Gobernadora in southern Orange County; within
the Coto de Caza gated community. Canada Gobernadora flows north to south and confluences with San
Juan Creek approximately 7.5 miles upstream of the Pacific Ocean. Portola Dam is an earth-filled
structure situated about 8 miles north of San Juan Creek with a maximum recycled water (or domestic
water blend) storage capacity of 586 acre-feet and a high-water elevation of 936 feet.
The Canada Gobernadora valley channel area between the dam and San Juan Creek has been developed
with a golf course and lined on each side by thousands of homes positioned just at or above the 100-year
flood plain. If a dam break occurred, the flow would likely destroy streets crossing the flood plain,
damage the water, sewer and recycled water pipeline infrastructure in them and may also affect some or
many home locations near the stream channel. Streets in Coto de Caza certain to be affected are: Trigo
Trail, Via Pajaro, Via Conejo, Vista Del Verde, San Miguel, Cantamar and South Bend Road. Along
with the golf course and the equestrian center, additional District facilities that are anticipated to be
damaged or destroyed by a dam break in Coto de Caza and farther downstream are:
• Coto Lift Station and force main
• South Ranch lift station and force main
• South County pipeline
• Ortega Lift Station (Talega) force mains
• Talega recycled water transmission main
• Chiquita Land Outfall pipeline
Per the compliance report, after entering San Juan Creek, the dam break inundation flood area would be
about the same as the 100-year flood plain all the way down to the Pacific Ocean.
Santiago Dam is an earth fill dam with a 25,000 acre-feet capacity reservoir (Irvine Lake). The dam is
jointly owned by the Irvine Ranch Water District and the Serrano Water District. Villa Park Dam is a
flood control dam located downstream from Santiago Dam. It is an earth-fill structure with a capacity of
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SECTION THREE Risk Assessment
15,600 acre-feet and is owned by the Orange County Flood Control District. Initial alerting is expected
from Dam keepers who are on duty at both Santiago Dam and Villa Park Dam.
Trabuco Dam is an earth-filled dam completed in 1984. The dam is located adjacent to the Robinson
Ranch residential community within the City of Rancho Santa Margarita, Orange County. The dam and
impounded reservoir is owned and operated by the Trabuco Canyon Water District (TCWD). TCWD
utilizes the reservoir to store up to approximately 135 acre-feet of reclaimed water produced from the
Robinson Ranch Wastewater Treatment Plant located adjacent to the reservoir. The reclaimed water can
be stored to an elevation of 127 4 feet, approximately 6 feet below the top of the dam crest's elevation of
1280 feet, MSL.
Upper Oso Reservoir (UOR) and Dam are located within the Cities of Mission Viejo and Rancho Santa
Margarita near the northern end of the Oso Creek watershed in southern Orange County. Upper Oso Dam
is an earth-filled structure situated between El Toro Road and Los Alisos Boulevard nearly 10 miles north
of the Trabuco Creek confluence point. UOR has a high-water elevation of 953 feet and stores up to 4000
acre-feet of recycled water for landscape irrigation that is mainly used within Santa Margarita and
Moulton Niguel Water Districts.
Immediately downstream of the UOR dam, a long bridge for State Route 241 crosses the flood channel
and may not experience problems during a major flood event. Just upstream of Los Alisos Boulevard,
some commercial property lies adjacent to the Oso Creek channel and may be affected. About three miles
downstream on Oso Creek and upstream of Olympiad Road, a large basin area was created (now a sports
park) to capture and attenuate major discharges from UOR before they enter Lake Mission Viejo (LMV).
LMV is created by a dam lying under Alicia Parkway. A UOR dam breach may also overflow LMV and
damage the dam to point where it could release stored water and create a catastrophic flood hazard all the
way to the Pacific Ocean.
Downstream of LMV, two golf courses have been developed within the Oso Creek channel area and
numerous commercial properties are on adjacent sides. Housing tracts have been built above the 100-year
flood plain but if a dam break occurred, the flow from UOR and LMV would likely destroy streets
crossing the flood plain and damage the water, sewer and recycled water pipeline infrastructure in them.
In addition to the many pipelines crossing the flood plain, District facilities that are anticipated to be
damaged or destroyed by a UOR dam break are:
• Eastbrook R W Pump Station
• Lakeside Pump Station
• South County Pipeline
• Oso Creek Water Reclamation Plant
• Oso Creek Trunk Sewer
• Oso Barrier R W Pump Station and Pipelines
Due to proximity and elevation, a considerable number of the residential and commercial properties in
many areas close to the banks of Oso Creek and farther downstream would likely be flooded for short
period of time and damaged. Streets in Mission Viejo and farther south likely to be affected by a dam
failure are: Los Alisos Boulevard, Santa Margarita Parkway, Olympiad Road, Alicia Parkway, Jeronimo
Road, Marguerite Parkway, Casta del Sol, La Paz Road, Oso Parkway, Interstate 5, Camino Capistrano,
Del Obispo Street, Stonehill Drive and Pacific Coast Highway.
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SECTION THREE Risk Assessment
Upper Chiquita Reservoir (UCR) -SMWD constructed the Upper Chiquita Reservoir to provide the
South Orange County region with substantial new water reserves to meet customer demand during
disruptions of water deliveries. These interruptions can be unanticipated, like the break of the Allen
McColloch Pipeline in 1999, or planned, like the shutdowns of the Diemer Filtration plant in Yorba Linda
to complete improvements or maintenance and repairs.
The Upper Chiquita Reservoir Emergency Storage Reservoir consists of an earthfill dam structure and a
covered, domestic water reservoir with a storage volume of 750 acre-feet. The reservoir footprint is
approximately 19.7 acres with a surface area of approximately 15.4 acres and has a High-Water Level
(HWL) of 860 feet.
In addition to the dam and reservoir, the site contains the following facilities:
• Floating Cover
• Access Roads
• Spillway and Drainage Facilities
• Inlet/Outlet Facilities and Pipelines
• Pump Station
• Disinfection Equipment
• Pipeline connection to the South Orange County Pipeline
The Upper Chiquita reservoir site is located on the western side of Chiquita Canyon north of Oso
Parkway and west of the current terminus of State Route 241 (SR-241) within the City of Rancho Santa
Margarita, east of the community of Las Flores in southern Orange County.
A portion of the site is encumbered within the Transportation Corridor Agency's (TCA) Chiquita Canyon
Perimeter Conservation Easement. The closest developed areas are the Tesoro High School campus
(located across Oso Parkway and south of the reservoir site) and the residential community of Las Flores
(approximately 0.8-mile west of the site). Additional land uses in the proximity to the reservoir site
include a neighborhood park, Crestview Park, located just over 300 feet west of the site, and the SMWD
Las Flores Reservoir, located approximately 250 feet west of the site.
Under an extreme catastrophic dam failure scenario, the flood zone would exceed the FEMA 100-year
floodplain in the Canada Chiquita Channel. Under this extreme scenario, land use categories that would
be affected include the Oso Parkway, SR-241 and the Tesoro High School. Once the flood waters reach
the San Juan Creek the flood flows would be less than the FEMA 100-year flood.
The Upper Chiquita Reservoir is located on the western slope of Chiquita Canyon, just north of Oso
Parkway in the City of Rancho Santa Margarita. Completed in October 2011, the 244 million-gallon
Upper Chiquita Reservoir is the largest domestic water reservoir built in south Orange County in nearly
45 years. Information regarding UCR:
• Storage capacity of approximately 244 million gallons of domestic water (750 acre-feet) is
contained in a lined and covered reservoir.
• Surface area of approximately 17.8 acres.
• A regional partnership between SMWD (lead agency), Moulton Niguel Water District, City of
San Juan Capistrano, City of San Clemente and South Coast Water District (storage owners).
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SECTION THREE Risk Assessment
• Capable of providing upwards of 168,000 families with approximately 200 gallons of fresh water
a day for one week.
• Included in the South Orange County Natural Community Conservation Plan, which designates
habitat conservation and species protection measures to ensure an environmentally sensitive
design.
• Reservoir is not visible from homes in local neighborhoods, including Las Flores and Wagon
Wheel.
• Earthen embankment significantly reduces any visual impacts while traveling west along Oso
Parkway near Highway 241.
• Reservoir design conforms to the rigorous standards set forth by the State of California.
• Safety features, including piezometers (moisture sensors), to continually monitor water levels and
test for irregularities.
3.2.4.4 Magnitude/Severity
Orange County's reservoirs range in capacity from 18 to 196,235 acre-feet of water storage. Inundation
maps and studies, when available, indicate the area that would be flooded and can be used to gauge the
severity of a dam failure.
A compliance analysis and inundation study report was prepared for Upper Oso Dam in 1979 to allow for
construction permitting by the State of California. This study indicated that if the dam was breached, a
potential maximum flow rate exceeding 250,000 cubic feet per second may be expected when the water
surface elevation drops to about 935 feet. Should such an event occur, the Upper Oso Reservoir could
potentially empty in about a half hour.
A similar report for Portola Dam was done in 1980. This study indicated that if the dam was breached, a
potential maximum flow rate of 22,645 cubic feet per second may be expected after about three hours
once the water surface elevation is at elevation 920 feet. Should such an event occur, Portola Dam would
potentially empty in just over six hours.
Failure of a reservoir or a dam could extend throughout most of the planning area, depending upon the
size of the facility and associated failure.
3.2.4.5 Probability of Future Occurrences
There has been just one incident involving a water storage structure in the 110 years since construction of
the first contemporary dam in Orange County. It is expected that future events will remain highly
unlikely, with a less than 1 percent chance of happening in any given year. However, such occurrences
have the potential to be highly destructive.
In the more than 50 years since the collapse of the Baldwin Hills Dam, there have been very few incidents
in California due to stringent standards, regulations, and regular inspections. The near-catastrophic
failure of the main spillway of the Oroville Dam in Northern California in 2017 is a reminder of the
ongoing risk presented by dams.
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SECTION THREE Risk Assessment
3.2.5 Drought
3.2.5.1 Description (Nature) of the Hazard
Many governmental utilities, the National Oceanic and Atmospheric Administration (NOAA) and the
California Department of Water Resources, as well as academic institutions, such as the University of
Nebraska-Lincoln's National Drought Mitigation Center, generally agree that there is no clear definition
of drought. Drought is highly variable depending on one's location within a state, the country or globe.
Drought in its simplest definition is an extremely dry climatic period where the available water falls
below a statistical average for a region. Drought is also defined by factors other than rainfall, including
vegetation conditions, agricultural productivity, soil moisture, water levels in reservoirs, and stream flow.
In effect, there are essentially three forms of drought: meteorological or hydrological drought, agricultural
drought, and regulatory drought:
• A meteorological or hydrological drought is typically defined when there is a prolonged period of
less than average precipitation resulting in the water level in aquifers, lakes, or above ground
storage reservoirs falling below sustainable levels.
• An agricultural drought occurs when there is insufficient moisture for an average crop yield.
Agricultural drought can be caused by the overuse of groundwater, poor management of
cultivated fields, as well as lack of precipitation.
• A regulatory drought can occur when the availability of water is reduced due to imposition of
regulatory restrictions on the diversion and export of water out of a watershed to another area. A
significant percentage of water in Southern California is imported from other regions (Colorado
River and Northern California) via aqueducts. Correspondingly, drought in California can be
made worse by water availability conditions in the regions at which the water originates.
An example of regulatory drought occurred between 1999 and 2004; a six-year drought on the
Colorado River basin, a major water supply for Southern California, resulted in a draw-down of
Colorado River water storage by more than 50%. More recently, beginning in 2008, regulatory
restriction in exporting water via the State Water Project combined with unusually dry weather
patterns resulted in two years of water rationing in Southern California. Additionally, a
meteorological drought can lead to regulatory restrictions; for example, California experienced
prolonged drought from 2013 to 2017, resulting in mandatory water restrictions for residents
through November 25, 2017.
Even distant droughts may have consequences for the plan area and participating jurisdictions.
The great drought of the 1930s, coined the "Dust Bowl," was geographically centered in the
Great Plains yet ultimately affected water shortages in California. The drought conditions in the
plains resulted in a large influx of people to the west coast. Approximately 350,000 people from
Arkansas and Oklahoma immigrated mainly to the Great Valley of California. As more people
moved into California, including Orange County, increases in intensive agriculture led to overuse
of the Santa Ana River watershed and groundwater resulting in regional water shortages.
Droughts cause public health and safety impacts, as well as economic and environmental impacts. Public
health and safety impacts are primarily associated with catastrophic wildfire risks and drinking water
shortage risks for small water systems in rural areas and private residential wells. Examples of other
impacts include costs to homeowners due to loss of residential landscaping, degradation of urban
Final I August 2019 3-21
SECTION THREE Risk Ass1ssm111
environments due to loss of landscaping, agricultural land fallowing and associated job loss, degradation
of fishery habitat, and tree mortality with damage to forest ecosystems. Drought conditions can also result
in damage to older infrastructure that is located within dry soils with potential to leak or break. Dead or
dying vegetation poses a risk to falling and damaging water and wastewater infrastructure systems.
In Orange County, drought conditions typically result in implementation of large-scale conservation
efforts, reducing water supplies to customers and altering the pricing system by implementing higher rates
for water usage that exceeds certain levels (e.g., wasteful). Higher rates that may be imposed during a
drought could have disproportionate impacts on lower-income households. Reduction in groundwater
supplies during drought conditions can also result in the need for water agencies that have high reliance
on local groundwater supplies to purchase larger amounts of imported water. Drought conditions have
also resulted in drier brush and an increase in the size and severity of wildfires. Water and wastewater
infrastructure systems located within areas susceptible to wildfires are at a greater risk of being impacted.
Damage or failure to water and wastewater infrastructure systems can significantly reduce or even
interrupt service to customers. For more on wildfire hazards, see Section 3.2.12. In addition, climate
change (see Section 3.2.1) may lead to more frequent and persistent droughts in the future.
Several bills have been introduced into Congress to mitigate the effects of drought. In 1998, President
Clinton signed into law the National Drought Policy Act, which called for the development of a national
drought policy or framework that integrates actions and responsibilities among all levels of government.
In addition, it established the National Drought Policy Commission to provide advice and
recommendations on the creation of an integrated federal policy. The most recent bill introduced into
Congress was the National Drought Preparedness Act of 2003, which established a comprehensive
national drought policy and statutorily authorized a lead federal utility for drought assistance. Currently
there exists only an ad-hoc response approach to drought unlike other disasters (e.g., hurricanes, floods,
and tornadoes) which are under the purview of FEMA.
3.2.5.2 History/Past Occurrences
Based on years of recorded water trends in Southern California, it is quite apparent that droughts and
water shortages can occur. Paleo records indicate that much more extreme events can occur than those
since historical record-keeping began. A significant drought, reported by many of the ranchers in
Southern California, occurred in 1860.
The National Drought Mitigation Center maintains a Drought Risk Atlas with historic data on drought
classifications throughout the United States. Based on the Palmer Drought Severity Index (PDSI), there
have been six occasions since records began in 1920 when the monitoring station in the City of Santa Ana
recorded "severe" or "extreme" drought conditions for a period of at least 12 months. These periods,
based on a "self-calibrating" PDSI, which uses data adjusted to be more sensitive to the local climate, are
listed in Table 3-4, Severe and Extreme SC-PDSI Drought Periods 1920-2012 Lasting 12 Months or
Longer (Santa Ana, CA) .16
16 NDMC. U.S. Drought Risk Atlas. http://droughtatlas.unl.edu/Data.aspx. Accessed March 2018.
Final I August 2019 3-22
SECTION THREE
Table 3-4
Severe and Extreme SC-PDSI Drought Periods 1920-2012
Lasting 12 Months or Longer (Santa Ana, CA)
Risk Assessment
Drougld. Start Dnnrpt&d Duration (Months)
February 1961 September 1963 31
March 1971 January 1978 82
May 1984 December 1992 103
January 1994 January 1995 12
December 1999 October 2004 58
January 2006 October 2010 57
The certified Drought Risk Atlas data does not yet include the historic, statewide drought that California
experienced within the last five years. Governor Jerry Brown proclaimed a State of Emergency in
January 2014; the declaration was not lifted until April 2017. In Orange County, precipitation totals were
well below average for five 12-month periods in arow. From July 2013 to June 2014, the weather station
in Santa Ana recorded just 4.4 inches or rain, about one-third of the normal annual amount.17
3.2.5.3 Location/Geographic Extent
Droughts occur over large regions and thus can affect the entire planning area.
3.2.5.4 Magnitude/Severity
Of the many varied indexes used to measure drought, the Palmer Drought Severity Index (PDSI) is the
most commonly used in the United States. Developed by meteorologist Wayne Palmer, the PDSI is used
to measure dryness based on recent temperature compared to the amount of precipitation. It utilizes a
number range, where 0 indicates normal conditions, negative numbers indicate drought, and positive
numbers indicate wet spells; refer to Table 3-5, Palmer Drought Severity Index.
Table 3-5
Palmer Drought Severity Index
DrOfllht WetSpells
-4.0 or less (Extreme Drought) +2.0 or +2.9 (Unusual Moist Spell)
-3.0 or -3.9 (Severe Drought) +3.0 or +3.9 (Very Moist Spell)
-2.0 or -2.9 (Moderate Drought) +4.0 or above (Extremely Moist)
-1.9 to +1.9 (Near Normal)
The PDSI is very effective at evaluation trends in the severity and frequency of prolonged periods of
drought, and conversely wet weather. NOAA publish weekly PDSI maps, which are also used by other
scientists to analyze the long-term trends associated with global warming and how this has affected
17 Orange County Public Works. Historic Rainfall Data. http://www.ocwatersheds.com/rainrecords/rainfalldata/
historic_ data.
Final I August 2019 3-23
SECTION THREE Risk Assessment
drought conditions. Figure 3-1 shows the current NOAA PDSI map for the week ending on March 17,
2018.
I /.
l I ,
f. r-
\'
~ \'
Figure 3-1
March 17, 2018 PDSI
Drought Severity Index by Division
Weekly Value for Period Ending Mar 17, 2018
Long Term Palmer
~ -,.,
DROUGHT SEVERITY INDEX (PALMER) \ ~ ~· , / ~ -, ,
DEPICTS PROLONGED (MONTHS, YEARS) ABNORMAL DRYNESS OR V \ _ ,
WETNESS: REPONDS SLOWLY; CHANGES LITTLE FROM WEEK lU WEEK;
AND REFLECTS LONG-TERM MOISTURE RUNOFF, RECHARGE, AND DEEP \ ' Based on preliminary data
PERCOLATION AS WELL AS EVAPOTRANSPIRATION. \
USES ... APPLICABLE IN MEASURING DISRUPTIVE EFFECTS OF PROLONGED DRYNESS \ .. · _(l
OR WETNESS ON WATER SENSffiVE ECONOMIES, DESIGNING DISASTER AREAS OF DROUGHT ~
OR WETNESS; AND REFLECTING THE GENERAL LONG-TERM STATUS OF WATER SUPPLIES
IN AQUIFERS, RESERVOIRS AND STREAMS. }!! -4.0 or less (Extreme Drought) +2.0 to +2.9 (Unusual Moist Spell)
LIMITATIONS ... JS NOT GENERALLY INDICATIVE OFFSHORT-TERM (FEW WEEKS) STATUS
OF DROUGHT OR WETNESS SUCH AS FREQUENTLY AFFECTS CROPS AND FIELD OPERATIONS
(THIS IS INDICATED BY THE CROP MOISTURE INDEX).
-3.0 to -3.9 (Severe Drought) +3.0 to +3.9 (Very Moist Spell)
-2.0 to -2.9 (Moderate Drought) • +4.0 and above (Extremely Moist)
--1.9 to +1.9 (Near Normal) •Missing/Incomplete
In 2014, at the peak of the statewide drought, the index assigned the extreme drought category to the
southern coastal California climate division for 40 consecutive weeks. Figure 3-2 shows the NOAA
PDSI for the week ending on July 26, 2014.
Final I August 2019 3-24
SECTION THREE
n-1.9 to +1 .9 (Near Normal l
Figure 3-2
July 26, 2014 PDSI
Risk Assessment
[Jj +4.0 and above !Extremely Moist)
The average duration of the droughts listed in Table 3-4, which includes drought periods classified as
severe or extreme, is 57 months.
3.2.5.5 Probability of Future Occurrences
The University of Nebraska-Lincoln has published PDSI maps analyzing trends over the past 100 years
(National Drought Mitigation Center 2005; Figure 1). In coastal southern California, from 1895 to 1995,
severe droughts occurred 10 to 15 percent of the time. From 1990 to 1995, severe droughts occurred 10
to 20 percent of the time.
Based on the droughts listed in Table 3-4, Orange County has been in severe or extreme drought for a
total of 343 months, or 31 percent of the time since 1920 and 54 percent of the time since 1960 (Note:
these calculations do not include the historic drought that officially ended in 2017).
Final I August 2019 3-25
SECTION THREE Risk Assessment
3.2.6 Earthquake Fault Rupture & Seismic Hazards (Ground Shaking & Liquefaction)
3.2.6.1 Description (Nature) of the Hazard
Earthquakes are considered a major threat to the County, especially when focusing on water and
wastewater facilities and pipelines that run throughout the County. A significant earthquake along one of
the major faults could cause substantial casualties, extensive damage to infrastructure, fires, and other
threats to life and property. Significant damages and outages of water and wastewater facilities could also
occur. The effects could be aggravated by aftershocks and by secondary effects such as fire, landslides
and dam failure. A major earthquake could be catastrophic in its effects on the population and could
exceed the response capability of the local communities and even the State.
Following major earthquakes, extensive search and rescue operations may be required to assist trapped or
injured persons. Emergency medical care, food/water and temporary shelter would be required for
injured or displaced persons. In the event of a truly catastrophic earthquake, identification and burial of
the dead would pose difficult problems. Mass evacuation may be essential to save lives. Emergency
operations could be seriously hampered by the loss of communications, damage to transportation routes
within, to, and out of the disaster area, and by the disruption of public utilities and services. With damage
to critical water and wastewater infrastructure there will be significant public health concerns, such as
dehydration or exposure to contaminated water, and the potential for reduced fire protection due to
limited sources of water. Facilities at greatest risk from severe earthquakes are dams and pipelines.
Additionally, damage to water and sewer lines that service commercial and industrial areas could have a
significant impact on the economy of the region. Extensive mutual aid for an extended period may be
required to bring water and wastewater services back online.
Earthquakes strike with little to no warning and they can have multiple impacts on an area. After effects
from an earthquake may include impacted roadways, downed power and communication lines, fires, and
damages to structures (especially poorly built, or those already in disrepair). Should a major event occur,
major damages and losses should be expected to pumping systems and wastewater treatment
infrastructure. Earthquakes are not a seasonal hazard, and thus can be experienced year-round. This fact
presents its own set of planning and preparedness concerns.
Seismic-specific building codes can provide MAs with reasonable guidance for structural mitigation. As
maintenance and potentially new building occurs within the planning area, seismic retrofitting is highly
recommended to prevent extensive damage to essential infrastructure.
For decades, partnerships have flourished between the United State Geological Survey (USGS), Cal Tech,
the California Geological Survey (CGS) and California universities to share research and educational
efforts with Californians. Tremendous earthquake mapping and mitigation efforts have been made in
California in the past two decades, and public awareness has risen remarkably during this time. Major
federal, state, and local government utilities and private organizations support earthquake risk reduction.
These partners have made significant contributions in reducing the adverse impacts of earthquakes.
Final I August 2019 3-26
SECTION THREE Risk Assessment
LIQUEFACTION
Liquefaction is the phenomenon that occurs when ground shaking causes groundwater to mix with the
soil. The mixture temporarily becomes a fluid and loses its strength. Liquefaction causes two types of
ground failure: lateral spread and loss of bearing strength. Lateral spreads develop on gentle slopes and
entails the sidelong movement of large masses of soil as an underlying layer liquefies. Loss of bearing
strength results when the soil supporting structures liquefies and causes structures to settle and/or collapse
from weakened foundations. Liquefaction can also occur independently of an earthquake, if any sudden
and significant stress causes the mixing of groundwater and soil. The risk of liquefaction depends on
several factors, including the height of the groundwater table and the types of soil in the area.
3.2.6.2 History/Past Occurrences
Southern California and Orange County have experienced several powerful earthquakes. The earliest
recorded earthquake in California occurred in Orange County in 1769. To better understand the potential
for damaging earthquakes in southern California, the scientific community has reviewed historical records
and conducted extensive research on faults that are the sources of the earthquakes occurring in southern
California. Historical earthquake records can generally be divided into records of the pre-instrumental
period and the instrumental period. In the absence of instrumentation, historic records of past earthquakes
are based on observations and the level of information is often dependent upon population density in the
area of the earthquake. Since California was sparsely populated in the 1800s, detailed information on pre-
instrumental earthquakes is relatively sparse. However, two very large earthquakes, the Fort Tejon in
1857 (M 7.9) and the Owens Valley in 1872 (M 7.6) are evidence of the tremendously damaging potential
of earthquakes in southern California. Other notable earthquakes that have impacted southern California
include the 1910 Glen Ivy Hot Springs earthquake (Elsinore Fault Zone, M 6.0), the 1933 Long Beach
earthquake (Newport-Inglewood Fault Zone, M 6.4), the 1952 Kem County and Lander earthquakes (M
7.3), the 1971 San Fernando earthquake (San Fernando Fault Zone, M 6.6), the 1987 Whittier earthquake
(Whittier Fault Zone, M 5.9), and the 1994 Northridge earthquake (Pico Thrust, M 6.7). The 1987
Whittier Quake caused damage to the Puente Hills Reservoir in La Habra and after inspection the
reservoir was found to have cracks in the concrete lining.
Damage from some of these earthquakes was limited because they occurred in areas which were sparsely
populated at the time they occurred. However, developed areas were much more severely affected.
Damage from the 1933 Long Beach earthquake was estimated at more than $40 million ($889 million in
2018 dollars), and 115 lives were lost. The seismic risk is much more severe today than in the past
because the population at risk is in the millions, rather than a few hundred or a few thousand persons.
Earthquakes of great magnitudes have caused lasting effects in developed regions.
The most recent significant earthquake event affecting southern California was the 1994 Northridge
Earthquake. At 4:31 A.M. on Monday, January 17, a moderate, but very damaging earthquake with a
magnitude of 6.7 struck the San Fernando Valley. In the following days and weeks, thousands of
aftershocks occurred, causing additional damage to affected structures. In this earthquake, 57 people
were killed and more than 1,500 people seriously injured. For days afterward, thousands of homes and
businesses were without electricity, tens of thousands had no gas, and nearly 50,000 had little or no water.
Out of the approximately 66,000 structures inspected, approximately 15,000 structures were moderately
to severely damaged, which left thousands of people temporarily homeless. Several collapsed bridges and
overpasses created commuter havoc on the freeway system. Extensive damage was caused by ground
shaking, but earthquake triggered liquefaction, and dozens of fires also caused additional severe damage.
The extremely strong ground motion felt in sizable portions of Los Angeles County resulted in record
Final J August 2019 3-27
SECTION THREE Risk Assessment
economic losses. The fact that the earthquake occurred early in the morning on a holiday considerably
reduced the potential effects. Many collapsed buildings were unoccupied, and most businesses were not
yet open. The direct and indirect economic losses ran into the tens of billions of dollars.
Clearly, no community in southern California is beyond the reach of a damaging earthquake. The
historical earthquake events that have affected southern California are listed below in Table 3-6,
Magnitude 5. 0 or Greater Earthquakes in the Southern California Region.
Table 3-6
Magnitude 5.0 or Greater Earthquakes in the Southern California Region
Date' l.oc:ati:ml11a9'11ade
1769 Los Angeles Basin (M 6.0) 1941 Carpentaria (M 5.9)
1800 San Diego Region (M 6.5) 1952 Kern County (M 7. 7)
1812 Wrightwood (M 7.0) 1954 West of Wheeler Ridge (M 5.9)
1812 Santa Barbara Channel (M 7.0) 1971 San Fernando (M 6.5)
1827 Los Angeles Region (M 5.5) 1973 Point Mugu (M 5.2)
1855 Los Angeles Region (M 6.0) 1979 Imperial Valley (6.5)
1857 Great Fort Tejon Earthquake (M 8.3) 1986 North Palm Springs (M 6.0)
1858 San Bernardino Region (M 6.0) 1987 Whittier Narrows (M 5.8)
1862 San Diego Region (M 6.0) 1990 Upland (M 5.7)
1892 San Jacinto or Elsinore Fault (M 6.5) 1991 Sierra Madre (M 5.6)
1893 Pico Canyon (M 5.8) 1992 Landers (M 7.3)
1894 Lytle Creek Region (M 6.0) 1992 Big Bear (M 6.2)
1894 E. of San Diego (M 5.8) 1994 North ridge (M 6. 7)
1899 Lytle Creek Region (M 5.8) 1999 Hector Mine (M 7 .1)
1899 San Jacinto and Hemet (M 6.4) 2004 San Luis Obispo (M unknown)
1907 San Bernardino Region (M 5.3) 2008 Greater Los Angeles Area (M 5.5)
1910 Glen Ivy Hot Springs (M 5.5) 2008 Borrego Springs (M 5.4)
1916 Tejon Pass Region (M 5.3) 2009 El Centro/Baja, Ca (M 5.9)
1918 San Jacinto (M 6.9) 2010 El Centro/Baja, Ca (M 7.2)
1923 San Bernardino Region (M 6.0) 2010 El Centro/Baja, Ca (M 5.7)
1925 Santa Barbara (M 6.3) 2014 La Habra (5.1)
1933 Long Beach (M 6.3)
Final I August 2019 3-28
SECTION THREE Risk Assessment
LIQUEFACTION
Comprehensive, historic accounts of damage to structures from liquefaction are not readily available.
Some damage caused by the Northridge earthquake of 1994, such as damage to the King Harbor area of
Redondo Beach in Los Angeles County, was due to liquefaction, as opposed to ground shaking.
3.2.6.3 Location/Geographic Extent
Nearly all of Orange County is at risk of moderate to extreme ground shaking. Figure 3-3 shows ground
shaking severity zones for Orange County. The areas most susceptible to damage from earthquakes based
on the shaking intensity hazard map include Yorba Linda Water District and the Cities of La Habra and
Buena Park. These communities can be severely impacted by landslides, liquefaction, extensive
infrastructure damage, fire, dam failure, and other secondary earthquake affects. A major earthquake
could be catastrophic in its effect on the population and could exceed the response capability of the local
communities and even the State. Although the above noted water/wastewater utilities are most likely to
experience "extreme" shaking, all of the County's water/wastewater utilities fall within a moderate to
extreme shaking intensity zone and therefore should expect the potential of damage from an earthquake.
The area at risk of fault rupture is limited to areas in the immediate vicinity of a fault. California began
extensive mapping of earthquake faults with the Alquist-Priolo Earthquake Fault Zoning Act of 1972.
Figure 3-4 shows both the fault zones in Orange County that have been mapped through the act. The
Whittier Fault Zone near the county's northern border passes through part of the Yorba Linda Water
District. The Newport-Inglewood Fault Zone parallels the coast in western Orange County.
There are many additional large faults that could affect Orange County in addition to the Whittier and
Newport-Inglewood-Rose Canyon faults. These include the Elsinore Fault, Peralta Fault, Puente Hills
Fault, San Andreas Fault, and San Jacinto Fault. Smaller faults include the Norwalk Fault and the El
Modena Faults. In addition, newly studied thrust faults, such as the San Joaquin Hills Fault could also
have a significant impact on the County. Each of the major fault systems are described briefly below and
are presented in alphabetical order. This order does not place more danger on one fault over another; it is
simply for organizational purposes.
• Elsinore Fault Zone I Whittier Fault I Chino Fault: Located in the northeast part of the county,
the Elsinore Fault Zone follows a general line easterly of the Santa Ana Mountains into Mexico.
The main trace of the fault zone is about 112 miles long. The last major earthquake on this fault
occurred in 1910 (M 6.0), and the interval between major ruptures is estimated to be about 250
years. Southern California Earthquake Center (SCEC) reports probable earthquake magnitudes
for the main trace of the Elsinore fault to be in the range of 6.5 to 7.5. At the northern end of the
Elsinore Fault zone, the fault splits into two segments: the 25-mile-long Whittier Fault (probable
magnitudes between 6.0 and 7.2), and the 25-mile-long Chino Fault (probable magnitudes
between 6.0 and 7.0). The location of the Whittier Fault makes it especially critical to the Diemer
Filtration Plant in Yorba Linda and pipelines bringing water into Orange County and/or from the
Diemer Plant which is located very near this fault.
Final I August 2019 3-29
SECTION THREE
Los Angeles
County
Figure 3-3
Ground Shaking Hazard
San Bernardino
County
Risk Assessment
Riverside County
Water Districts Infrastructure
• Reservoirs
• MET Diemer Filtration Plant
• Water Treatment Plant
Iii Wastewater Treatment Plant
Potable Local
MET/Joint Agency Pipe Lines Ground Shaking
--Local Sewer Lines Susceptability
--Regional Sewer Lines
Outfall Lines
Force Mains
Water Agency Boundary
Moderate
.. High
.. Extreme
N W+E
s
2.5 10
.~~~~~M~il-es~~~__j__J
ORANGE COUNTY
POTABLE AND WASTEWATER INFRASTRUCTURE
Final I August 2019
San Diego County
3-30
SECTION THREE
Los Angeles
. County
Water Districts Infrastructure
• Reservoirs
• MET Diemer Filtration Plant
• Water Treatment Plant
li1 wastewater Treatment Plant
Potable Local
MET/Joint Agency Pipe Lines
--Local Sewer Lines
--Regional Sewer Lines
Outfall Lines
Force Mains
Water Agency Boundary
Figure 3-4
Alquist-Priolo Rupture Zones
San Bernardino
County
Risk Assessment
Riverside County
Earthquake
Hazard
Alquist-Priolo Rupture
Zone ~5 10
~~--'---1._MTies-~· ~·--•-!
ORANGE COUNTY
San Diego County
POTABLE AND WASTEWATER INFRASTRUCTURE
Final I August 2019 3-31
SECTION THREE Risk Assessment
• Newport-Inglewood-Rose Canyon Fault Zone: This fault zone extends from the Santa Monica
Mountains in a southeast direction through the western part of Orange County, then continues
offshore (not more than four miles from the coast) down to San Diego Bay. Originally, this was
thought to have been two separate systems; the Newport-Inglewood Fault and the Rose Canyon
Fault Line. However, a study prepared in March 2017 found that they are in fact one continuous
fault line with three main stepovers. This fault line was the source of the destructive 1933 Long
Beach earthquake (magnitude 6.4), which caused 120 deaths and considerable property damage.
SCEC reports probable earthquake magnitudes for the Newport-Inglewood fault to be in the
range of 6.0 to 7.4.
• Peralta Hills Fault: Limited information is available to paleoseismically characterize the fault
and no studies have been undertaken to determine the timing of earthquakes. There is a strong
geomorphic expression along Lincoln Boulevard west of Tustin A venue in the City of Orange.
Some believe the fault is not active while others believe it is active. On-going research has linked
the fault as a back thrust with the Elsinore Fault, with a potential magnitude of 6.8.
• Puente Hills Thrust Fault: This is another recently discovered blind thrust fault that runs from
northern Orange County to downtown Los Angeles. It is now known to be the source of the 1987
Whittier Narrows earthquake. Recent studies indicate that this fault has experienced four major
earthquakes ranging in magnitude from 7.2 to 7.5 in the past 11,000 years, but that the recurrence
interval for these large events is on the order of several thousand years.
• San Andreas Fault Zone: As the dominant active fault in California, it is the main element of the
boundary between the Pacific and North American tectonic plates. The longest and most
publicized fault in California, it extends approximately 650 miles from Cape Mendocino in
northern California to east of San Bernardino in southern California and is approximately 35
miles northeast of Orange County. This fault was the source of the 1906 San Francisco
earthquake, which resulted in some 700 deaths and millions of dollars in damage. It is the
southern section of this fault that is currently of greatest concern to the scientific community.
Geologists can demonstrate that at least eight major earthquakes (Richter Magnitude 7.0 and
larger) have occurred along the southern San Andreas Fault in the past 1,200 years with an
average spacing in time of 140 years, plus or minus 30 years. The last such event occurred in
1857 (Fort Tejon earthquake). Based on that evidence and other geophysical observations, the
Working Group on California Earthquake Probabilities (SCEC, 1995) has estimated the
probability of a similar rupture (M 7.8) in the next 30 years (1994 through 2024) to be about 50
percent. The range of probable magnitudes on the San Andreas Fault Zone is reported to be 6.8
to 8.0.
• San Jacinto Fault Zone: The San Jacinto fault zone is located approximately 30 miles north and
east of the county. The interval between ruptures on this 130-mile-long fault zone has been
estimated by SCEC to be between 100 and 300 years, per segment. The most recent event ( 1968
M6.5) occurred on the southern half of the Coyote Creek segment. SCEC reports probable
earthquake magnitudes for the San Jacinto fault zone to be in the range of 6.5 to 7.5.
• San Joaquin Hills Fault: This fault is a recently discovered southwest-dipping blind thrust fault
originating near the southern end of the Newport-Inglewood Fault close to Huntington Beach, at
the western margins of the San Joaquin Hills. Rupture of the entire area of this blind thrust fault
could generate an earthquake as large as magnitude 7.3. In addition, a minimum average
Final I August 2019 3-32
SECTION THREE Risk Assessment
recurrence interval of between about 1650 and 3100 years has been estimated for moderate-sized
earthquakes on this fault (Grant and others, 1999).
In addition to the major faults described above, the rupture of several smaller faults could potentially
impact Orange County, including the Norwalk Fault (located in the north of the county in the Fullerton
area) and the El Modeno Fault (located in the City of Orange area).
In 2005, MWDOC hired Earth Consultants International to prepare specific ground acceleration and
shaking maps for five fault earthquake scenarios in Orange County. Table 3-7, Characteristics of
Important Geologic Faults in Orange County, summarizes the characteristics of these five major geologic
faults. Earthquake maps for the individual jurisdictions are included in the Jurisdictional Annexes.
Table 3-7
Characteristics of Important Geologic Faults in Orange County
Blind thrust Blind thrust
1 +/-0.5 Unknown, Prob. <1 0.7 +/-0.4 0.5 +/-0.2 2.5 +/-1.0
6.9 6.8 7.5 6.6 6.8
Recurrence Interval 2,200-3,900 Unknown 2,750 1,600-3, 100 1, 100
Last Activi M6.3 in 1933 Unknown <3,000 200-300 1,600-2,000
Figure 3-5, prepared for the California Domestic Water Corp., a private wholesaler, shows the location of
earthquake epicenters from 1941 to 2013 in and around Orange County, which is outlined in the center of
the map.
Earthquakes that occur outside of southern California and Orange County could also have a significant
impact on drinking water supplies. Such scenarios include disruptions of the Colorado River Aqueduct,
the State Water Project (especially at an area such as the Edmonston Pumping Station and Porter Tunnel
bringing water over and through the Tehachapi), and in the Bay-Delta Region, where failure of levees and
flooding of islands with salt water from San Francisco Bay could disrupt water supplies for months or
years. Orange County is 50 percent dependent on supplies from beyond its borders to meet the drinking
water needs. This leaves it exposed to these occurrences from outside the region.
Final I August 2019 3-33
SECTION THREE Risk Assessment
Figure 3-5
Location of Earthquake Faults Bounding the CDWC Service Area and Orange County
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Final I August 2019
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3-34
SECTION THREE Risk Assessment
LIQUEFACTION
The potential for liquefaction exists in areas susceptible to ground shaking with loose soils and/or shallow
groundwater. Given the active faults in the region and the presence of geologically young,
unconsolidated sediments and hydraulic fills, liquefaction is possible throughout much of Orange County.
The California Geological Survey's Seismic Hazards Zonation Program identifies and maps areas prone
to liquefaction. These zones for Orange County are shown in Figure 3-6. The most extensive
liquefaction zones occur in coastal areas, including parts of Huntington Beach and Newport Beach, and
along Upper Newport Bay. In addition, a 2016 Seismic Hazard Assessment conducted by GeoPentech,
Inc. found that the highest liquefaction hazard areas are the flat, coastal portions of the planning area, and
the risk decreases moving inland. The areas identified as being highly susceptible to liquefaction are the
San Juan Creek/San Clemente Beach areas.
3.2.6.4 Magnitude/Severity
Ground shaking is measured using either the moment magnitude scale (MMS, denoted as Mw or simply
M) or the Modified Mercalli Intensity Scale. The MMS is a replacement for the Richter scale, which is
still often referred to but is no longer actively used, as the Richter scale is not reliable when measuring
large earthquakes.18 The weakest earthquakes measured by the MMS start at 1.0, with the numbers
increasing with the strength of the earthquake. The strongest recorded earthquake, which struck Chile in
1960, measured 9.5 on the MMS.19 Like the Richter scale, the MMS is a logarithmic scale, meaning the
difference in strength between two earthquakes is much larger than the difference in their measurements.
For example, a 6.0 Mw earthquake is 1,000 times stronger than a 4.0 Mw earthquake and about 1.4 times
as strong as a 5.9 Mw event.
The Modified Mercalli Intensity Scale is based on the damage caused by the earthquake and how it is
perceived, rather than an actual measurement. When comparing multiple earthquakes, one event may
have a higher Mercalli rating than another even if it released less energy, and thus was measured lower on
the MMS. The Mercalli scale ranges from I (instrumental, rarely felt by people) to XII (catastrophic, total
damage and lines of sight are distorted). Table 3-8, Comparison ofMMS and Modified Mercalli Intensity
Scale, shows a general comparison between the MMS and the Modified Mercalli Intensity Scale. Note
that there is some overlap toward the higher end of the Mercalli ratings, with certain intensities produced
by multiple ranges of magnitude measurements.
18 2014. "Moment Magnitude, Richter Scale." https://www.usgs.gov/faqs/moment-magnitude-richter-scale-what-are-
different-magnitude-scales-and-why-are-there-so-many.
19 2015. "Earthquake Lists, Maps, and Statistics." https://earthquake.usgs.gov/earthquakes/browse/.
Final I August 2019 3-35
SECTION THREE
Los Angeles
County
Water Districts Infrastructure
e Reservoirs
• MET Diemer Filtration Plant
• Water Treatment Plant
~ Wastewater Treatment Plant
Potable Local
MET/Joint Agency Pipe Lines
--Local Sewer Lines
--Regional Sewer Lines
Outfall Lines
-----Force Mains
Water Agency Boundary
Figure 3-6
Liquefaction Susceptibility Zones
Liquefaction
Susceptability
.. Very High
High
Moderate
.. Unknown
San Bernardino
County
2.5
ORANGE COUNTY
N W+E
s
Miles
Risk Assessment
Riverside County
San Diego County
POTABLE AND WASTEWATER INFRASTRUCTURE
Final I August 2019 3-36
SECTION THREE Risk Assessment
Table 3-8
Comparison of MMS and Modified Mercalli Intensity Scale
llapitude .CRS).
llodiiecl •rcali fmensiy Scale
.lldensiy Descripfon.
1.0 to 3.0 I Not felt except by very few persons under especially favorable conditions.
II Weak: Felt only by a few persons at rest, especially on upper floors of buildings.
3.0 to 3.9 Weak: Felt quite noticeably by persons indoors, especially on upper floors of buildings.
Ill Many people do not recognize it as an earthquake. Standing motor cars may rock slightly.
Vibrations similar to the passing of a truck. Duration estimated.
Light: Felt indoors by many, outdoors by few during the day. At night, some awakened.
IV Dishes, windows, doors disturbed; walls make cracking sound. Sensation like heavy truck
4.0 to 4.9 striking building. Standing motor cars rocked noticeably.
v Moderate: Felt by nearly everyone; many awakened. Some dishes, windows broken.
Unstable objects overturned. Pendulum clocks may stop.
VI Strong: Felt by all, many frightened. Some heavy furniture moved; a few instances of
5.0 to fallen plaster. Damage slight.
5.9 Very Strong: Damage negligible in buildings of good design and construction; slight to
VII moderate in well-built ordinary structures; considerable damage in poorly built or badly
designed structures; some chimneys broken.
Severe: Damage slight in specially designed structures; considerable damage in ordinary
6.0 to 6.9 VIII substantial buildings with partial collapse. Damage great in poorly built structures. Fall of
chimneys, factory stacks, columns, monuments, walls. Heavy furniture overturned.
Violent: Damage considerable in specially designed structures; well-designed frame
IX structures thrown out of plumb. Damage great in substantial buildings, with partial
7.0 and collapse. Buildings shifted off foundations.
greater Extreme: Some well-built wooden structures destroyed; most masonry and frame x structures destroyed with foundations. Rails bent.
XI Extreme: Few, if any (masonry) structures remain standing. Bridges destroyed. Rails
bent greatly.
XII Extreme: Damage total. Lines of sight and level are distorted. Objects thrown into the air.
Source: USGS 2017.
Final I August 2019 3-37
SECTION THREE Risk Assessment
Several faults in Orange County can produce severe to extreme earthquakes. The SCEC and the Working
Group on California Earthquake Probabilities have determined the probable magnitude for an earthquake
along these major faults:
• Elsinore Fault Zone: SCEC reports probable earthquake magnitudes for the main trace of the
Elsinore fault to be in the range of 6.5 to 7.5. The two northern segments, the Whittier Fault and
the Chino Fault, have probable magnitudes of 6.0 to 7.2 and 6.0 to 7.0, respectively. The Whittier
Fault location is extremely critical because it crosses the two main sources of untreated water
being brought into the County (Yorba Linda Feeder and the Lower Feeder) and it passes very
close to the Diemer Filtration Plant which serves as the treatment facility for the bulk of Orange
County. Metropolitan does not have a backup system to supply treated water to many parts of
central and southern Orange County in the event of an outage of the Diemer Plant.
• Newport-Inglewood Fault Zone: SCEC reports probable earthquake magnitudes for the Newport-
Inglewood fault to be in the range of 6.0 to 7.4.
• Puente Hills Thrust Fault: Recent studies indicate that this fault has experienced four major
earthquakes ranging in magnitude from 7.2 to 7.5 in the past 11,000 years, but that the recurrence
interval for these large events is on the order of several thousand years.
• Peralta Hills Fault: The Earth Consultants International study for MWDOC indicates that this
may be a back thrust fault to the Elsinore fault and may be capable of a magnitude 6.8.
• San Andreas Fault Zone: Based on that evidence and other geophysical observations, the fault
has estimated the probability of a rupture with a magnitude 7.8 in the next 30 years ( 1994 through
2024) to be about 50 percent (SCEC, 1995). The range of probable magnitudes on the San
Andreas Fault Zone during this period is reported to be 6.8 to 8.0.
• San Joaquin Hills Fault: Recent reports have determined that the blind thrust fault can generate
an earthquake as large as 7 .3. In addition, a minimum average recurrence interval of 1650 to
3 100 years has been estimated for moderate-sized earthquakes on this fault.
• San Jacinto Fault Zone: SCEC reports probable earthquake magnitudes for the San Jacinto fault
zone to be in the range of 6.5 to 7.5.
Although the San Andreas Fault Zone can produce an earthquake with a magnitude greater than 8.0 M,
some of the smaller faults have the potential to inflict greater damage on the urban core of the Los
Angeles Basin. Seismologists believe that a 6.0 earthquake on the Newport-Inglewood Fault Zone would
result in far more death and destruction than a larger earthquake on the San Andreas Fault Zone, due to
the San Andreas' relatively remote location from the urban centers of southern California.
3.2.6.5 Probability of Future Occurrences
Based on the amount of seismic activity that occurs within the region, there is no doubt that communities
within the jurisdictional boundaries of MWDOC will continue to experience future earthquake events. It
is reasonable to expect that a major event (5.0 M or higher) and possibly even more severe will occur
within a 30-year timeframe.
Final I August 2019 3-38
SECTION THREE Risk Assessment
The Third Uniform California Earthquake Rupture Forecast (UCERF3), developed in 2014 by the
Working Group on California Earthquake Probabilities and led by the USGS, provides estimates of the
magnitude, location, and likelihood of fault rupture for more than 350 fault segments throughout the state.
For Southern California, the study estimated the likelihood of a 6.0 M earthquake at 100 percent, a 7.0
earthquake at 75 percent, and an 8.0 earthquake at 7 percent.20
Predicted ground shaking patterns throughout southern California for hypothetical scenario earthquakes
are available from the USGS as part of their on-going "ShakeMap" program. These maps are provided in
terms of Instrumental Intensity, which is essentially Modified Mercalli Intensity estimated from
instrumental ground motion recordings. ShakeMaps in graphical and GIS formats are available on the
USGS website at: https://earthquake.usgs.gov/data/shakemap/.
In 2014, USGS released a simplified Peak Ground Acceleration (PGA) map to demonstrate the 2 percent
probability of exceedance within a 50-year time period; refer to Figure 3-7. This analysis was done at the
nationwide level and can be seen in the figure below. California, and many parts of southern California,
have a risk of high PGA at this probability level.
Figure 3-7
Peak Ground Acceleration with 2 Percent Probability in 50 Years for the United States
110
.:{I
Two-percent probability of cxcccdancc in 50 years map of peak ground acceleration
20 https://pubs.usgs.gov/fs/2015/3009/pdf/fs2015-3009. pdf.
Final I August 2019 3-39
SECTION THREE Risk Assessment
3.2.7 Flood
3.2.7.1 Description (Nature) of the Hazard
Flooding may result from heavy rains raising water levels in rivers and streams; storms, tides, and
weather patterns pushing ocean water into coastal areas; and when debris blocks normal storm water
drainage systems. Other causes are discussed in more detail elsewhere in the plan, including sea-level
rise in Section 3.2.1 and dam/reservoir failure in Section 3.2.4. Flooding can happen fast and with little
warning, or water levels may rise slowly over the course of several days.
Orange County's terrain makes it naturally susceptible to flooding. Many of the rivers, creeks, and
streams flow through natural floodplains on their way to the ocean. The County's rapid growth and
transformation from an agricultural community to an urban community has changed flood-control
practices in the region. Drainage is managed through reservoirs, dams, diversion structures and
developed plains. In addition, seven pump stations (Huntington Beach, Cypress, Seal Beach, Los
Alamitos, Rossmoor, Harbor-Edinger, and South Park) regulate storm water discharge to flood control
channels. Although there is a countywide system of flood-control facilities, many of these are not
designed for or capable of conveying runoff from major storms.
Orange County also has a warning system in place to detect potential flooding. The County began
installing its ALERT (Automated Local Evaluation in Real Time) system in 1983. Operated by the
County's Environmental Resources Section of the Resource Development and Management Department
(RDMD) in cooperation with the National Weather Service, ALERT uses remote sensors located in
rivers, channels and creeks to transmit environmental data to a central computer in real time. Sensors are
installed along the Santa Ana River, San Juan Creek, Arroyo Trabuco Creek, Oso Creek, Aliso Creek, as
well as flood control channels and basins. The field sensors transmit hydro logic and other data (e.g.,
precipitation data, water levels, temperature, wind speed, etc.) to base station computers for display and
analysis.
3.2.7.2 History/Past Occurrences
Residents reported damaging floods caused by the Santa Ana River as early as 1770 (as recorded by
explorer and missionary Father Juan Crespi). Major floods in Orange County along the Santa Ana River
occurred in 1810, 1815, 1825, 1862, 1884, 1891, 1916, 1927, 1938, 1969, 1983, 1993, 1995, 1998, 2005,
2010, and 2017. Often these events involved additional hazards, such as landslides, mud flows, and high
winds. Table 3-9, Presidential Disaster Declarations for Flooding in Orange County Since 1969, lists
Presidential Disaster Declarations since 1969 that involved flooding and affected Orange County.
Final I August 2019 3-40
SECTION THREE Risk Assessment
Table 3-9
Presidential Disaster Declarations for Flooding in Orange County Since 1969
Disaster Incident Type Tile Incident lllcident
Number BeginDate EndDate
'
4305 Flood Severe winter storms, flooding, and mudslides. 1/18/2017 1/23/2017
1952 Flood Severe winter storms, flooding, and debris and mud flows. 12/17 /2010 1/4/2011
1585 Severe Storm(s) Severe storms, flooding, landslides, and mud/debris flows. 2/16/2005 212312005
1577 Severe Storm( s) Severe storms, flooding, debris flows, and mudslides. 12/27/2004 1/11/2005
1203 Severe Storm(s) Severe winter storms and flooding. 2/2/1998 4/30/1998
1046 Severe Storm(s) Severe winter storms, flooding landslides, mud flow. 2/13/1995 4/19/1995
1044 Severe Storm( s) Severe winter storms, flooding, landslides, mud flows. 1/3/1995 2/10/1995
979 Flood Severe winter storm, mud & landslides, and flooding. 1/5/1993 3/20/1993
935 Flood Rain/snow/wind storms, flooding, mudslides. 2/10/1992 2/18/1992
812 Flood Severe storms, high tides and flooding. 1/17/1988 1/22/1988
677 Coastal Storm Coastal storms, floods, slides and tornadoes. 1/21/1983 3/30/1983
615 Flood Severe storms, mudslides and flooding. 1/8/1980 1/8/1980
547 Flood Coastal storms, mudslides and flooding. 2/15/1978 2/15/1978
253 Flood Severe storms and flooding. 1/26/1969 1/26/1969
The most significant flood events to affect the county are summarized below:
• Great Flood ofl 862. The flood of January 1862, called the Noachian deluge of California, was
unusual in two ways: 1) the storm causing the flood occurred during a very severe drought
spanning 1856 to 1864; and 2) the flood lasted 20 days, which is considered an extremely long
duration. Under normal circumstances, major floods last only a few days. The only structure left
standing along this portion of the Santa Ana River was the Aqua Mansa chapel and residents
gathered on the small point of high-land to take refuge from the storm. Miraculously, there were
no recorded deaths.
• Great Flood of1916. On January 27, 1916, flood waters inundated a large area along the Santa
Ana River, including Main Street in downtown Santa Ana, where the water was 3 feet deep.
Adjacent farm lands, which later became the City of Westminster, also flooded. Three vehicular
bridges and three railroad bridges were washed away by the flood and four people drowned.
• Great Flood of 1938. The flood of 1938 is considered the most devastating flood to occur in
Orange County during the 20th Century and affected all Southern California. The storm began on
February 27 and lasted until March 3. In the Santa Ana Basin, 34 people died, and 182,300 acres
were flooded. All buildings in Anaheim were damaged or destroyed. Two major railroad
bridges, seven vehicular bridges, and the town of Atwood were destroyed. The Santa Ana River
inundated the northwestern portion of Orange County and train service to and from Santa Ana
was cancelled. The maximum discharge on March 3, 1938 was 46,300 cfs, with a gage height at
10.20 feet. Damage exceeded $50 million.
• Great Flood of 1969. The floods of January and February 1969 were the most destructive on
record in Orange County. Previous floods had greater potential for destruction, but the County
Final I August 2019 3-41
SECTION THREE Risk Assessment
was relatively undeveloped when they occurred. During the flood of 1969, rain fell almost
continuously from January 18 to January 25, resulting in widespread flooding. Orange County
was declared a national disaster area on February 5. A second storm hit on February 21 and
lasted until February 25 bringing rain to the already saturated ground. This second storm
culminated in a disastrous flood on February 25. The storm resulted in the largest peak outflow
from Santiago Reservoir since its inception in 1933. The reservoir at Villa Park Dam reached its
capacity for the first time since its construction in 1963; the dam had a maximum inflow of
11,000 cfs. The outlet conduit was releasing up to 4,000 cfs yet the spillway overflowed at 1 :30
p.m. and continued for 36 hours. The maximum peak outflow from the dam reached 6,000 cfs.
Although the safety of the dam was never threatened the outflow caused serious erosion
downstream in the cities of Orange and Santa Ana and in some parks and golf courses. A
Southern Pacific Railroad bridge, water and sewer lines, a pedestrian over crossing, and three
roads washed out. Approximately 2,000 Orange and Santa Ana residents were evacuated from
houses bordering Santiago Creek.
• Great Flood of 1983. An intense downpour and high tides associated with El Nifio (due to the
presence of a low-pressure system) caused intense shoreline flooding. Meanwhile the Santa Ana
River crested its sides near the mouth of the ocean; creating a disaster for the low-lying areas of
Huntington Beach; floodwaters were 3 to 5 feet deep.
• 1992 Coastal Storms. In 1992, several coastal storms affected many coastal utilities storm drain
and sewage treatment processes. SOCW A reported significant cracks and damage to its Aliso
Creek Ocean outfall.
• Great Floods of1993. El Nifio caused more flooding. An intense storm was concentrated in the
Laguna Canyon Channel area extending from Lake Forest to downtown Laguna Beach. In spite
of a valiant effort to save downtown merchants by sandbagging, the stores were flooded. Laguna
Canyon Road was damaged extensively, as well as homes and small businesses in the Laguna
Canyon Channel. There were no fatalities reported.
• Great Flood of 1995. A disaster was declared in Orange County after extremely heavy and
intense rains exceeded the storm runoff capacity of local drainage systems in many Orange
County cities and regional Flood Control District systems. As a result, widespread flooding of
homes and businesses occurred throughout these cities. There were approximately 1,000 people
evacuated and extensive damage sustained to both private and public property.
• Great Floods of1997/1998. El Nifio Storms that occurred during this period created extensive
storm damage to private property and public infrastructure, with damages reaching approximately
$50 million. Storm conditions caused numerous countywide mudslides, road closures, and
channel erosion. Hillside erosion and mudslides forced the continual clearing of roads of fallen
trees and debris. Protective measures, such as stabilizing hillside road slopes with rock or K-rail
at the toe of slopes, were taken to keep the normal flow of transportation. Harbors, beaches,
parks, and trails also sustained substantial storm damage.
• 201012011 Winter Storms. On January 26, California received Presidential Declaration for the
Severe Winter Storms, Flooding, and Debris and Mud Flows that occurred December 17, 2010
through January 4, 2011. At the time of the declaration the State of California incurred well over
$75 million in damages, while Orange County sustained over $36 million in damages. Orange
Final I August 2019 3-42
SECTION THREE Risk Assessment
County sustained extensive damage sustained to private and public property, as well as critical
infrastructure.
• 2017 Winter Storms.21 Southern California experienced three storms over six days starting on
January 18. The heavy rains, combined with already saturated soil, produced flash flooding
across much of Orange County. Streets flooded with 1 to 3 feet of water in Huntington Beach,
Santa Ana, and Newport Beach. Responders conducted rescue operations on the Santa Ana River
in the cities of Orange and Huntington Beach. The storms resulted in a Presidential Disaster
Declaration for 16 counties throughout the state.
3.2.7.3 Location/Geographic Extent
Orange County covers 789 square miles and its landscape varies from mountainous terrain (in the
northeast and southeast) to floodplains (in the central and western section). Figure 3-8 identifies the 100-
and 500-year FEMA floodplains within the County. A sizable portion of north Orange County, including
some of the County's most densely populated areas, is within a 500-year floodplain, which denotes areas
with a one-in-500, or 0.2 percent, chance of flooding in any given year. These floodplains are further
explained in Sections 3.2.7.4 and 3.2.7.5.
The Santa Ana River, flowing through the heart of Orange County to the Pacific Ocean, is the County's
greatest flood threat. Other areas subject to flooding during severe storms include areas adjacent to
Atwood Channel, Brea Creek Channel, Fullerton Creek Channel, Carbon Creek Channel, San Juan Creek
Channel, and East Garden Grove-Wintersburg Channel. Areas adjacent to Santiago Creek and Collins
Channel in the central portion of the County and large portions of the San Diego Creek watershed in the
City of Irvine and unincorporated areas of the County are also subject to inundation. In the southern
portion of the county, canyon areas are subject to flooding. The continued development in these areas has
made the flood hazard even greater.
3.2.7.4 Magnitude/Severity
Flood severity is often described in terms of a 100-year flood, describing an event that is likely to occur
once in a 100-year period. In other words, there is a 1 percent probability of an event this severe
occurring in any given year. Flood Insurance Rate Map (FIRM) panels produced by FEMA identify areas
subject to this level of risk as being within the 100-year floodplain. Figure 3-8 shows these locations
throughout Orange County, as well as a 500-year floodplain, which indicates a 0.2 percent annual chance
of flooding.
Floods can also be measured in terms of data collected by U.S. Geological Survey through a nationwide
system of stream gages. The primary gage on the Santa Ana River is in the City of Santa Ana. During
the Great Flood of 1938, this gage measured a water level of 10.2 feet, compared to a normal height of
about 1.44 feet. During both two most recent flood events in 2010/2011 and 2017, the river reached 7.6
feet.
21 NCEI. Storm Events Database. https://www.ncdc.noaa.gov/stormevents/eventdetails.jsp?id=676168; and The
Orange County Register. January 23, 2017. Flooding, mudslides, power outages follow torrential rainstorm. https://www.
ocregister.com/2017/01 /23/flooding-mudslides-power-outages-follow-torrential-rainstorm/.
Final I August 2019 3-43
SECTION THREE
Los Angeles
County
Water Districts Infrastructure
• Reservoirs
• MET Diemer Filtration Plant
• Water Treatment Plant
Iii Wastewater Treatment Plant
Potable Local
MET/Joint Agency Pipe Lines
--Local Sewer Lines
--Regional Sewer Lines
Outfall Lines
Force Mains
Water Agency Boundary
Flood Zones
Figure 3-8
Flood Zones
San Bernardino
County
2.5
Risk Assessment
Riverside County
San Diego County
5 10
.. FEMA 100 Year
.. FEMA 500 Year
~~-~--'---MJles-1--~· -~' ___ J
ORANGE COUNTY
POTABLE AND WASTEWATER INFRASTRUCTURE
Final I August 2019 3-44
SECTION THREE Risk Assessment
The greatest flood in terms of water flow occurred in 1862, when the Santa Ana River saw an estimated
flow rate of317,000 cubic feet per second (cfs). This flood was three times greater than the Great Flood
of 1938 which had an estimated flow of 110,000 cfs. Peak discharges measured on the Santa Ana River
during declared flood disasters since 1993 have ranged from 8,220 to 31, 700 cfs.
On December 22, 2010, during the peak of that winter's floods, a weather station in Silverado Canyon
recorded more than 7 inches of rain in a single day, according to NOAA climate data. During other flood
events in the last 25 years, the maximum daily rainfall recorded within Orange County has ranged from 2
to 4 inches.
3.2.7.5 Probability of Future Occurrences
As mentioned in Section 3.2.7.4, FIRM panels depict areas that have a 1 percent chance of flooding in
any given year, identified as a 100-year floodplain, as well as a 0.2 percent chance, or a 500-year
floodplain. Such areas within Orange County are depicted in Figure 3-8.
3.2.8 Geologic Hazards (Expansive Soils & Land Subsidence)
3.2.8.1 Description (Nature) of the Hazard
EXPANSIVE SOILS
According to a scientific paper published in the Journal of Geotechnical Engineering (Day 1994 ),
"expansive soil is a worldwide problem that causes extensive damage to civil engineering structures."
Expansive soils are particularly problematic in the southwestern United States and especially in southern
California, where there are large clay deposits compounded by "alternating periods of rainfall and
drought." The problem with constructing on expansive soils is that the clay, often referred to as adobe,
expands rapidly during the rainy season and contracts gradually during the dry season causing "shrink-
swell." Shrink-swell is particularly problematic for "slab-on-grade" foundations which can be placed
directly on expansive soil which are constantly in a state of movement as the soil expands and contracts
causing the foundation to fatigue and crack. Buildings with balloon frame construction are also
susceptible to bowing and cracking when built on expansive soils. Shrink and swell can affect
water/wastewater facilities particularly buildings or structures built using slab on grade or balloon frame
construction techniques.
Expansive soil is also known to "creep" on unstable slopes eventually leading to landslides. Typically,
this is found when expansive soil underlies compact topsoil. As the expansive soil expands-contracts, the
compact topsoil slides or creeps downhill. Facilities built on unstable slopes with underlying expansive
soils are prone to movement and can be damaged or destroyed in extreme circumstances.
LAND SUBSIDENCE
The United States Geological Survey (USGS) defines land subsidence as a gradual settling or sudden
sinking of the ground surface because of subsurface movement of underlying geologic units. Scientists at
the USGS have determined that nearly 17,000 square miles in 45 states have been directly affected by
land subsidence, caused by aquifer-system compaction, drainage of organic soils, underground mining,
hydro-compaction, natural compaction, sinkholes, and thawing permafrost. More than 80 percent of land
subsidence is caused by over-use of groundwater and the increasing development of land and water
resources threatens to worsen existing land-subsidence problems (while initiating) new ones.
Final I August 2019 3-45
SECTION THREE Risk Assessment
Land subsidence in California is mainly caused by groundwater pumping in areas where aquifer recharge
is exceeded. Known as "over-drafting," the dewatering of aquifers has led to lower water tables and
subsidence, resulting in damage to infrastructure, water quality and in coastal areas has resulted in the
intrusion of seawater. USGS notes "the compaction of unconsolidated aquifer systems that can
accompany excessive groundwater pumping is by far the single largest cause of subsidence" and "the
overdraft of such aquifer systems has resulted in permanent subsidence and related ground failures," thus
"the extraction of this resource for economic gain constitutes 'groundwater mining' in the truest sense of
the term." Over-drafting is further exacerbated in hot geographic regions with a large population; this
includes much of the southern California.
3.2.8.2 History/Past Occurrences
EXPANSIVE SOILS
In 1980, Krohn and Slosson ( 1980) made an assessment and cost estimate of the damage caused by
expansive soils throughout the United States. They estimated that approximately $7 billion in property
damage was reportedly attributed to construction on expansive soils. While no recent figures have been
identified, the increase in construction activity in areas of expansive soil, especially in southern
California, will undoubtedly cause this number to increase. J. David Rogers of the University of Missouri
found that "expansive soils are the second leading cause of property damage in the United States."
There are no reported occurrences of expansive soils causing considerable damage within the County;
although expansive soils are known to exist. Typically, expansive soils would be identified at a local
level on a site-by-site or area basis and are addressed as part of the development review process.
LAND SUBSIDENCE
The relationship between subsidence and groundwater pumping was not fully recognized until 1928 when
O.E. Meinzer, scientist with the United States Forest Service (USFS), realized that aquifers were
compressible. By the 1950s, the USGS made a concerted effort to measure the amount of ground
subsidence. In 1952, Joseph Poland studied large discrepancies between the U.S. Coast and Geodetic
Survey for the Santa Clara and San Joaquin valleys. Poland noted that the increased use of groundwater
correlated with the amount of ground subsidence. Poland's work led to the verification of "consolidation
theory" or compressible aquifers, as well as leading to the development of "definitions, methods of
quantification, and confirmation of the interrelationship among hydraulic-head declines, aquitard (clay)
compaction, and land subsidence."
Subsidence has historically occurred in Orange County associated with groundwater pumping and from
peat decomposition. The areas of historic subsidence associated with groundwater pumping are
illustrated in Figure 3-9, below. Localized subsidence possibly due to peat decomposition has also been
reported in scattered areas inland from the coast between Sunset and Newport Beaches.
3.2.8.3 Location/Geographic Extent
EXPANSIVE SOILS
According to the County of Orange General Plan Safety Element, much of Orange County is covered by
soil that may cause cracking in concrete foundations. The most prevalent problems occur from clay or
"expansive" soils that contract and expand. Problems attributed to expansive soils are usually related to
Final I August 2019 3-46
SECTION THREE Risk Assessment
improperly designed or constructed foundations. Due to the diversity of soil conditions, structures are not
completely safe from cracking, slipping, or sinking to some degree. Expansive soils are typically
mitigated through structural and design regulations as well as through soil treatment techniques. The
California Building Code specifically addresses expansive soils in Sections 1804.4, 1806.5 and 1815.
The California Health and Safety Code Section 17954 states that "If the preliminary soil report indicates
the presence of critically expansive soils or other soil problems which, if not corrected, would lead to
structural defects, such ordinance shall require a soil investigation of each lot in the subdivision" and
"The soil investigation shall be prepared by a civil engineer who is registered in this state." Expansive
soils can impact the entire planning area.
LAND SUBSIDENCE
Currently, land subsidence affects much of the west coast. The major land-subsidence affected area of
Orange County exists between Newport Beach and Huntington Beach and five miles inland from this
point. This area is referred to as the Talbert Gap, which formed millennia ago from alluvial deposition
from the Santa Ana River.
According to the USGS online map viewer, areas starting from Newport Beach up to Seal Beach, and out
east to Placentia, experience subsidence impacts due to groundwater pumping. Figure 3-9, shows the
areas impacted by subsidence.
Final I August 2019
Figure 3-9
Subsidence
t:•lt::=d
L~ttJUfl.:i
J-l!IJ'.
3-47
SECTION THREE Risk Assessment
3.2.8.4 Magnitude/Severity
EXPANSIVE SOILS
Damages to property due to erosion and deposition are usually classified as cosmetic, functional, or
structural. Cosmetic damages refer to slight problems where only the physical appearance of a structure
is affected (e.g., cracking in plaster or drywall). Functional damages refer to situations where the use of a
structure has been impacted due to subsidence. Structural damages include situations where entire
foundations require replacement due to subsidence-caused cracking of supporting walls and footings.
Buildings and infrastructure across Orange County are vulnerable to the impacts of soil expansion,
instability, and erosion-related hazards. Cities in southern California have established guidelines for
construction in areas of expansive soils. The MAs generally conduct soil surveys prior to construction of
water and wastewater facilities and take the specific circumstances into consideration during design and
construction. The magnitude and severity of expansive soils are similar throughout the planning area.
LAND SUBSIDENCE
The Talbert Gap, as described above, has sustained nearly a century of underground water aquifer
pumping which was used to sustain intensive grazing and agriculture practices. By 1956 the water table
had lowered to below sea level allowing saltwater from the Pacific Ocean to intrude through the Talbert
Gap. Because of studies identifying subsidence and saltwater intrusion in Orange County, OCWD began
a massive management program to minimize the loss of aquifer-stored water and reduce saltwater
intrusion. Although subsidence is a concern within Orange County, programs have been implemented to
address subsidence issues. The MAs within the portion of the planning area identified as having historic
subsidence could continue to be impacted if it is not monitored and addressed.
3.2.8.5 Probability of Future Occurrences
EXPANSIVE SOILS
Expansive soils will continue to occur throughout the planning area. Potential impacts associated with
these hazards will need to be addressed through site design and development review, including
preparation and adherence to geotechnical constraints recommendations.
LAND SUBSIDENCE
In areas that have experienced decreased precipitation in the summer months and reduced surface-water
supplies, communities are often forced to pump more ground water to meet their needs. Orange County
has historically experienced long term-droughts, especially in recent years. Although specific areas of
excessive pumping, such as Talbert Gap, have been addressed, there is still a high probability that
communities within the planning area will continue to experience impacts of these events.
It is important that these communities consider future mitigation actions that will address this hazard,
particularly in newly developing areas near water. In areas where groundwater pumping has caused
subsidence, switching to surface water supplies can be instrumental. Changing climate norms are
expected to affect soil resources and especially during hot, dry years annual grasses that stabilize and
protect topsoil often fail to germinate or do not grow well. This leaves soil surfaces highly vulnerable to
Final I August 2019 3-48
SECTION THREE Risk Assessment
erosion from wind and precipitation and can further exacerbate the consequences of soil expansion and
subsidence.
3.2.9 High Winds/Santa Ana Winds
3.2.9.1 Description (Nature) of the Hazard
High winds are defined as those that last longer than one hour at greater than 39 miles per hour (mph) or
for any length of time at greater than 57 mph. High winds that affect Orange County, notably Santa Ana
winds, are generally defined as warm, dry winds that blow from the east or northeast (offshore). Santa
Ana winds often blow with exceptional speed in the Santa Ana Canyon and forecasters at the National
Weather Service in Oxnard and San Diego usually place speed minimums on these winds and reserve the
use of "Santa Ana" for winds greater than 25 knots. The complex topography of southern California
combined with various atmospheric conditions creates numerous scenarios that may cause widespread or
isolated Santa Ana events. Commonly, Santa Ana winds develop when a region of high pressure builds
over the Great Basin (the high plateau east of the Sierra Mountains and west of the Rocky Mountains
including most of Nevada and Utah). Clockwise circulation around the center of this high-pressure area
forces air down slope from the high plateau. The air warms as it descends toward the California coast at
the rate of 5 degrees Fahrenheit per 1,000 feet due to compression of the air mass. The air is dry since it
originated in the desert, and it dries out even more as it is compressed.
3.2.9.2 History/Past Occurrences
Most high wind incidents in the planning area are the result of Santa Ana wind conditions. While high
impact wind incidents are not frequent in the area, significant Santa Ana wind events have impacted the
County. The National Oceanic and Atmospheric Administration (NOAA) Storm Events Database
identifies 145 events reported within Orange County between December 1, 1950 and December 31, 2017.
Table 3-10, Major High Wind Events, identifies and describes some of the major events occurring within
Orange County.
3.2.9.3 Location/Geographic Extent
Santa Ana winds blow westward through the canyons toward the coastal areas of southern California.
Orange County commonly experiences Santa Ana winds between October and March. The winds are not
location specific, but rather impact the entire planning area.
3.2.9.4 Magnitude/Severity
Wind speeds are typically 35 knots through and below passes and canyons with gusts to 50 knots.
Stronger Santa Ana winds can have gusts greater than 60 knots over widespread areas with gusts greater
than 100 knots in some areas. Frequently, the strongest winds in the basin occur during the night and
morning hours due to the absence of a sea breeze. The sea breeze which typically blows onshore daily,
can moderate the Santa Ana winds during the late morning and afternoon hours. Santa Ana winds are an
important forecast challenge because of the high fire danger associated with them. Santa Ana winds can
adversely affect power utilities that have transformers and power lines, in tum affecting the ability of
some water and wastewater utilities to operate when back-up generation is unavailable. The magnitude
and severity of Santa Ana winds are similar throughout the planning area.
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Table 3-10
Major High Wind Events ....... Property
Date Localon Cfds) Damage Desaiption
(dOllars)
Severely disrupted transportation, power, and daily
North East Orange activities. Broken trees and power poles were common
12/9/1998 81 50,000 throughout the area and power was knocked out to County 180,000 customers. Downed power lines also started
several wild fires, damaging one house.
Most of the major highways in the Inland Empire and
Santa Ana Mountains through the Santa Ana Mountains were closed, partially
12/3/1999 and Foothills 104 20,000 due to two semi-tractor trailers that overturned, partially
from blowing dust reducing visibility, and partially from
road signs and other debris being blown onto the roads.
3120-Santa Ana Mountains Damage ranged from downed power poles, trees falling
3/21/2000 and Foothills 51 25,000 on cars and houses, fruit being knocked off of trees,
and blowing sand and dust lowering visibility to zero.
Numerous trees and power poles were blown down. At
least 60 communities were affected. A commuter train
was delayed for several hours in Orange County when
Santa Ana Mountains power poles were blown down onto the track. A brush
1/5 -1/7/2003 and Foothills fire whipped by the winds, damaged 5 houses and
burned 150 acres. Sparks from downed power lines
started numerous small brush fires, but these were
quickly contained. Many houses and at least 300
parked automobiles were damaged by falling trees.
11/23/03 Santa Ana Mountains 50 50,000 Trees, power lines, and signs were knocked down.
and Foothills
12/16/04 Northeast Orange 68 20,000
213105 Santa Ana Mountains 53 5,000 and Foothills
3/31/05 Northeast Orange 54 5,000 Strong Santa Ana winds caused power outages, blew
over big riqs, and knocked down trees.
Surface high pressure over the Great Basin resulted in
gusty Santa Ana winds from the San Bernardino
Santa Ana Mountains mountains, through the Inland Empire, and into Orange
1/22/06 and Foothills 62 15,000 County. Wind gusts over 60 mph toppled trees and
power poles. Downed power lines caused sporadic
power outages. Most of the property damage that
occurred came as a direct result of falling trees.
Santa Ana Mountains Santa Ana winds toppled trees, brought down power
and Foothills/Orange lines, and knocked out power to thousands in many
10/21-22/2007 74 100,000 parts of Orange County. The strongest winds were felt County Coastal along the foothills of the Santa Ana mountains and near Areas the Chino Hills area.
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12/16/11
1/14/14
2/12/16
2/17/17
12/4/17
Santa Ana Mountains
and Foothills
Santa Ana Mountains
and Foothills
Orange County
Inland
Orange County
Coastal
Orange County
Inland
Risk Assessment
Table 3-10 [continued]
Major High Wind Events
56
67
52
52
52
15,000
2,000
20,000
75,000
15,000
This system set off intense showers and isolated
thunderstorms with pea-sized hail (accumulations in
Rancho Cucamonga and Mission Viejo), as well as
several funnel clouds spotted east of John Wayne
Airport. Most of the rain with this system was confined
to Orange County, the Inland Empire and the northern
mountains. Heavy rain was observed in Orange County
and the Inland Empire on the 15th and 16th with
locations there recording between one-quarter and one-
half inch. Strong winds were also observed with this
storm, especially on the 16th, which was a more
widespread wind event than early December, impacting
all counties, including San Diego County, with warning-
level winds. Several wind gusts of 45-65 mph were
reported in the Santa Ana Mountains, the Inland Empire
and San Diego County Mountains. Several trees and
power poles were downed, leaving many without power.
Power poles were reported down in Yorba Linda and
around 240 customers were reported without power in
Tustin.
The highest wind gusts occurred in the San Diego
County foothills and inland Orange County, including
the Santa Ana Mountains. Winds downed fiber optic
lines near Santiaqo Canyon in Oranqe County.
Strong northeasterly winds downed numerous trees
near Irvine, Santa Ana and Orange. Approximately 85
customers lost power in the city of Santa Ana.
A strong trough and associated Pacific cold front swept
into southern California from the west, bringing strong
winds, heavy snow and rain. The storm was
noteworthy for the strong prefrontal southerly winds that
produced significant tree damage over the coast and
valleys. In the mountains the ski resorts received 1-2 ft
of snow, while elevations as low as 5,000 ft saw a few
inches of accumulation. Rainfall ranged from 2-6
inches along the coastal slopes to 1-2 inches at the
coast. At the beaches surf heights reached 8 to 12 ft.
An isolated peak gust of 60 mph occurred at San
Clemente Pier. Numerous trees were downed over the
coastal areas.
Report of a large tree downed by strong winds in
Orange. Tree damage, minor roof damage, and an
exploding transformer were also reported in Santa Ana.
Notes: kts = knots. One (1) knot is equal to 1.151 miles per hour (mph).
National Oceanic and Atmospheric Administration, National Centers for Environmental Information, Storm Events Database, Event Types:
High Winds, https://www.ncdc.noaa.gov/stormevents/choosedates.jsp?statefips=6,CALIFORNIA, accessed March 21, 2018.
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3.2.9.5 Probability of Future Occurrences
High winds, including Santa Ana winds, will continue to occur annually in the County. The probability
of future occurrence throughout the planning area is high.
3.2.10 Landslide/Mudflow
3.2.10.1 Description (Nature) of the Hazard
Landslide is a general term for a falling mass of soil or rocks. Mudflow consists of material that is wet
enough to flow rapidly and contains at least 50 percent sand, silt, and clay-sized particles. The primary
effects of landslides/ mudflows can include:
• Abrupt depression and lateral displacement of hillside surfaces over distances of up to several
hundreds of feet.
• Disruption of surface drainage.
• Blockage of flood control channels and roadways.
• Displacement or destruction of improvements such as roadways, buildings, and water wells.
Landslides are a type of 'mass wasting' which denotes any down slope movement of soil and rock under
the direct influence of gravity. The term 'landslide' encompasses events such as rock falls, topples,
slides, spreads, and flows. Landslides can be initiated by rainfall, earthquakes, volcanic activity, changes
in groundwater, disturbance and change of a slope by man-made construction activities, or any
combination of these factors. Landslides can occur underwater, causing tidal waves and damage to
coastal areas. These landslides are called submarine landslides (USGS Fact Sheet 0071-40, Version 1.0).
Failure of a slope occurs when the force that is pulling the slope downward (gravity) exceeds the strength
of the earth materials that compose the slope. They can move slowly, (millimeters per year) or can move
quickly and disastrously, as is the case with debris-flows. Debris-flows can travel down a hillside of
speeds up to 200 miles per hour (more commonly, 30 -50 miles per hour), depending on the slope angle,
water content, and type of earth and debris in the flow. These flows are initiated by heavy, usually
sustained, periods of rainfall, but sometimes can happen because of short bursts of concentrated rainfall in
susceptible areas. Burned areas charred by wildfires are particularly susceptible to debris flows, given
certain soil characteristics and slope conditions.
A debris or mud flow is a river of rock, earth and other materials, including vegetation that is saturated
with water. This high percentage of water gives the debris flow a very rapid rate of movement down a
slope. This high rate of speed makes debris flows extremely dangerous to people and property in its path.
Earthquakes often trigger flows. Debris flows normally occur when a landslide moves down-slope as a
semi-fluid mass scouring, or partially scouring soils from the slope along its path. Flows are typically
rapid moving and also tend to increase in volume as they scour out the channel. Flows often occur during
heavy rainfall, can occur on gentle slopes, and can move rapidly for large distances.
Wildland fires on hills covered with chaparral are often a precursor to debris flows in burned out canyons.
The extreme heat of a wildfire can create a soil condition in which the earth becomes impervious to water
by creating a waxy-like layer just below the ground surface. Since the water cannot be absorbed into the
soil, it rapidly accumulates on slopes, often gathering loose particles of soil into a sheet of mud and
debris. Debris flows can often originate miles away from unsuspecting persons, and approach them at a
high rate of speed with little warning.
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Natural processes can cause landslides or re-activate historical landslide sites. The removal or
undercutting of shoreline-supporting material along bodies of water by currents and waves produces
countless small slides each year. Seismic tremors can trigger landslides on slopes historically known to
have landslide movement. Earthquakes can also cause additional failure (lateral spreading) that can occur
on gentle slopes above steep streams and riverbanks.
3.2.10.2 History/Past Occurrences
The following identifies some of the more major landslide occurrences within Orange County. There
have been no disaster declarations within Orange County associated with landslides/mudflows.
• 1978 Bluebird Canyon. Orange County. The cost of recovery was $52. 7 million (2000 dollars)
with 60 houses destroyed or damaged. Unusually heavy rains in March of 1978 may have
contributed to initiation of the landslide. Although the 1978 slide area was approximately 3.5
acres, it is suspected to be a portion of a larger, ancient landslide.
• 1980 Southern California Slides. The damage was estimated at $1.1 billion in 2000 dollars.
Heavy winter rainfall in 1979-80 caused damage in six southern California counties. In 1980, the
rainstorm started on February 8 with 5 days of continuous rain and 7 inches of precipitation.
Slope failures were beginning to develop by February 15 and then very high-intensity rainfall
occurred on February 16. As much as 8 inches ofrain fell in a six-hour period in many locations.
Records and personal observations in the field on February 16 and 17 showed that the mountains
and slopes literally fell apart on those two days.
• 1983 San Clemente, Orange County. The damage to California Highway 1 was estimated at $65
million in 2000 dollars. Litigation at that time involved approximately $43. 7 million (2000
dollars).
• 1994 Northridze. California Earthquake Landslides. As a result of the magnitude 6.7
Northridge, California, earthquake, more than 11,000 landslides occurred over an area of 10,000
km2. Most were in the Santa Susana Mountains and in mountains north of the Santa Clara River
Valley. They destroyed dozens of homes, blocked roads, and damaged oil-field infrastructure. It
caused deaths from Coccidioidomycosis (valley fever) the spore of which was released from the
soil by the landslide activity and blown toward the coastal populated areas.
• March 1995 Los Angeles and Ventura Counties, Southern California. Above normal rainfall
triggered damaging debris flows, deep-seated landslides, and flooding. Several deep-seated
landslides were triggered by the storms, the most notable was the La Conchita landslide, which in
combination with a local debris flow, destroyed or badly damaged 11 to 12 homes in the small
town of La Conchita, about 20 km west of Ventura. There also was widespread debris-flow and
flood damage to homes, commercial buildings, and roads and highways in areas along the Malibu
coast that had been devastated by wildfire 2 years before.
• 1998 Laguna Niguel, Orange County, Landslide. During the 1997 /1998 El Nino Season, heavy
rainfall increased movement on the site of an ancient landslide in Laguna Niguel. The storms in
December 1997 had accelerated its movement and in early 1998, a crumbling hillside forced the
evacuation of 10 hilltop homes and more than 10 condominium units resting below. Ultimately
four of the hilltop homes collapsed, falling down hillside into the void created by the slide area.
The condominium complex has since been demolished and the site remains open space.
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• 2005 Blue Bird Canyon, Laguna Beach. Orange County; Landslide. On June 1, 2005, Bluebird
Canyon in Laguna Beach experienced a landslide. Exceptionally heavy rainfall during the winter
period was the underlying cause of the instability in an ancient landslide. A 30-acre piece of
hillside between 50 to 60 feet deep broke free and fell on the homes below; 15 homes were
destroyed, and 32 others had varying levels of damage. The approximate cost of damage was
about $35 million.
• 2005 SCWD Landslide Impact to the Joint Regional Transmission Line. Following a year of
heavy rainfall, a slope failure occurred in Laguna Niguel in an area that included a section of the
Joint Regional Transmission Pipeline. The pipeline had to be shut down and a temporary pipeline
was routed around the slide area while evaluations of the stability of the area were made.
Ultimately, the pipeline will be rerouted around the unstable area or located back in the slope
after it has stabilized. Because the problem occurred in the winter/spring period and there are
other pipelines into South Orange County, no water shortages were experienced.
• 2018 Cannon Clift Dana Point. Orange County; Rockslide. Approximately 18 tons of rocks,
including a two-ton boulder dropped from the cliff area under Cannons Restaurant and struck a
public restroom across from Baby Beach at the north end of Dana Point Harbor. The rocks are
part of a four-to -five-million-year-old rock formation called the Capistrano Formation.
Rain induced landslides were reported in Santa Margarita in 1980, 1993, 1995 and 2005. In 1980 rains
washed out an access road in Coto De Caza uncovering an 8-inch water line. The same series of storms
also exposed a 21-inch trunk sewer line along the Oso Creek in Mission Viejo resulting in damages of
$300,000. In 1993 bank failures caused many pipelines to break which had to be replaced, relocated, or
re-protected at a cost of nearly 2.1 million dollars. A slope failure in 1995 caused pipeline failures
costing nearly $30,000 and in 2005 a reservoir slope failure in Talega Valley cost $350,000. Landslides,
resulting in erosion along Aliso Creek, affected the South Orange County Water Authority's Aliso Creek
Effluent Transmission Main (a 36-inch pipeline carrying treated wastewater).
3.2.10.3 Location/Geographic Extent
Figure 3-10 illustrates the portions of the planning area susceptible to landslides based upon topography,
surface and subsurface geology, borehole data, historical ground-water levels, existing landslide features,
slope gradient, rock-strength measurements, geologic structure, and probabilistic earthquake shaking
estimates. These areas are primarily comprised of the southern coastal communities and the communities
containing steeper topography or located adjacent to mountain areas.
The extent of landslides/mudflows varies throughout the County depending upon the location and
contributing conditions, such as an earthquake, heavy rain or recent fires. Earthquake-induced landslides
are relatively shallow falls and slides, in which highly disrupted masses of rock and soil travel down
slopes at high speed. The Northridge earthquake, in Los Angeles County, triggered more than 11,000
landslides in an area of 6,200 square miles. Most slides were shallow, brittle failures of surficial rock and
soil.
Deep-seated landslides are triggered by cumulative rainfall during long periods (weeks to years).
Resulting landslides are relatively deep earth flows and translational or rotational earth slides and rock
slides. Translational landslides are typically a few meters to tens of meters deep, and rotational slides
range in depth from several meters to tens of meters. Deep-seated translational and rotational landslides,
including rock slides, tend to fail a little at a time and move more slowly than debris flows, but a few do
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accelerate to rapid movement. A previous landslide within the County due to over saturated soils resulted
in a 40-foot landslide below a five-million-gallon water tank. Other landslides in the county have
measured approximately 3 .5 acres and 25 acres.
Similarly, short-duration, intense rainfall, generally greater than 0.5-inch per hour has the potential to
trigger post-fire debris flows. These flows can extend several miles. Documented debris flows from
burned areas in southern California and the western United States have ranged in volume from as small as
600 cubic meters to as much as about 300,000 cubic meters. This larger volume is enough material to
cover a football field with mud, rocks, and debris to about 65 meters deep.
3.2.10.4 Magnitude/Severity
Factors included in assessing landslide magnitude/severity include population and property distribution in
the hazard area, the frequency of landslide or debris flow occurrences, slope steepness, soil
characteristics, and precipitation intensity. The California Geological Survey landslide maps prepared as
part of the Seismic Hazard Program (refer to Figure 3-10) indicate the extent of landslide susceptibility
within the County, which includes the southernmost coastal areas and eastern areas of the County. These
areas would also be more likely to experience mudflows due to the topography of the areas.
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Los Angeles
. County
Water Districts Infrastructure
• Reservoirs
• MET Diemer Filtration Plant
• Water Treatment Plant
fiim wastewater Treatment Plant
Potable Local
MET/Joint Agency Pipe Lines
--Local Sewer Lines
--Regional Sewer Lines
Outfall Lines
Force Mains
Water Agency Boundary
Figure 3-10
Landslide Susceptibility
San Bernardino
County
Risk Assessment
Riverside County
Landslide
Hazard
.. Landslide Hazard 2.5 10
~-_L_~~-' Miles
ORANGE COUNTY
San Diego County
POTABLE AND WASTEWATER INFRASTRUCTURE
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3.2.10.1 Probability of Future Occurrences
A study conducted by Nature Geoscience in 2015 indicated that the projected upsurge of El Nino and La
Nina events will increase the likelihood that coastal communities will experience erosion and flooding.
This is separate from sea level rise, which has also been identified as a cause of future hazard
vulnerabilities. In addition to erosion and flooding, the onset of El Nino and La Nina events will also
increase the magnitude and severity of mudflow events. The more recent wildfires also contribute to the
probability of mudflows in the event of more intense rainfall over a short duration. Earthquakes of
magnitude 4.0 and greater have been known to trigger landslides. The potential for an earthquake to
induce a landslide is highly dependent upon the location of the earthquake and magnitude in relation to a
landslide area. Based on previous landslide and mudflow incidents, along with studies predicting future
occurrences, it is reasonable to state that these hazards will continue to impact the jurisdictions identified
within the landslide susceptibility areas of the County. According to the Planning Team ranking,
landslides and mudflows are somewhat likely -having between a 1 % and 10% probability in next year or
a recurrence interval of 11 to 100 years.
3.2.11 Tsunami
3.2.11.1 Description (Nature) of the Hazard
The phenomenon we call "tsunami" is a series of traveling ocean waves of extremely long length
generated primarily by earthquakes occurring below or near the ocean floor. In the deep ocean, the
tsunami waves move across the deep ocean with a speed exceeding 500 miles per hour, and a wave height
of only a few inches. Tsunami waves are distinguished from ordinary ocean waves by their great length
between wave crests, often exceeding 60 miles or more in the deep ocean, and by the time between these
crests, ranging from 10 minutes to an hour.
As they reach the shallow waters of the coast, the waves slow down, and the water can pile up into a wall
of destruction up to 30 feet or more in height. The effect can be amplified where a bay, underwater
features, or harbor or lagoon funnels the wave as it moves inland. Large tsunamis have been known to
rise over 100 feet. Even tsunamis one to three feet high can be very destructive and cause many deaths
and injuries.
There are many causes of tsunamis, but the most prevalent is earthquakes. In addition, landslides,
volcanic eruptions, explosions, and even the impact of meteorites can generate tsunamis. Not all
earthquakes generate tsunamis. To generate a tsunami, the fault where the earthquake occurs must be
underneath or near the ocean and cause vertical movement of the sea floor over a large area, hundreds or
thousands of square miles. By far the most destructive tsunamis are generated from large, shallow
earthquakes with an epicenter or fault line near or on the ocean floor. The amount of vertical and
horizontal motion of the sea floor, the area over which it occurs, the simultaneous occurrence of slumping
of underwater sediments due to the shaking, and the efficiency with which energy is transferred from the
earth's crust to the ocean water are all part of the tsunami generation mechanism. The sudden vertical
displacements over such large areas disturb the ocean's surface, displace water, and generate destructive
tsunami waves. Although all oceanic regions of the world can experience tsunamis, the most destructive
and repeated occurrences of tsunamis are in the Pacific Rim region.
Tsunami waves can travel at the speed of a commercial jet plane, over 500 miles per hour, moving from
one side of the Pacific Ocean to the other in less than a day. This great speed makes it important to be
aware of the tsunami as soon as it is generated. Scientists can predict when a tsunami will arrive at
Final I August 2019 3-57
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various locations by knowing the source characteristics of the earthquake that generated the tsunami and
the characteristics of the sea floor along the path to the shore from the point of origin.
Offshore and coastal features can determine the size and impact of tsunami waves. Reefs, bays, entrances
to rivers, undersea features and the slope of the beach all modify the tsunami as it converges on the
coastline. People living near areas where large earthquakes occur may find that the tsunami waves can
reach their shores within minutes of the earthquake. For these reasons, the tsunami threat to many areas
such as Alaska, the Philippines, Japan and the United States West Coast can be immediate (for tsunamis
from nearby earthquakes which take only a few minutes to reach coastal areas) or less urgent (for
tsunamis from distant earthquakes which take from three to 22 hours to reach coastal areas). When a
tsunami reaches the coastline and moves inland, the water level can rise several feet, flooding homes,
businesses and infrastructure from several thousand feet to miles inland, depending on the topography.
Scientists cannot accurately predict when earthquakes will occur, and as a result they cannot determine
exactly when a tsunami will be generated or how destructive it will be. However, past tsunami height
measurements are useful in predicting future tsunami impact and flooding limits at specific coastal
locations and communities.
3.2.11.2 History/Past Occurrences
Tsunamis can be categorized as Pacific-wide or "local." Typically, a Pacific-wide tsunami is generated
by a major vertical shift in the ocean floor creating a wave that includes the entire column of water that
has the potential to travel long distances. A "local" tsunami can be a component of a Pacific-wide
tsunami in the immediate area of the earthquake, or a wave that is confined to the area of generation; such
as a landslide within a bay or harbor. Worldwide, tsunamis have resulted in loss of thousands of lives,
billions of dollars in damages, and the closure of many local economies.
All of the coastal areas in Orange County are susceptible to tsunamis, although most tsunamis have
occurred in Northern California. The Channel Islands were impacted by a tsunami in the early 1800s. In
the 1930s, four tsunamis struck the Los Angeles, Orange County, and San Diego coastal areas. In Orange
County the tsunami wave reached heights of approximately 20 feet above sea level. In 1964, following
the Alaska 8.2 earthquake, tidal surges of approximately 4 feet to 5 feet battered Huntington Harbor
causing moderate damages.
According to the OCSD Emergency Management Division, two events generated response by their
office:22
• April 1. 2014. An 8.2 earthquake off the coast of Chile had the potential to generate a tsunami
that could impact the Orange County coastline. The event was monitored, but no watch,
advisory, or warning was issued for the County.
• September 16. 2015. An 8.3 earthquake off the coast of Chile triggered a Tsunami Advisory for
the Orange County coastline. The Orange County EOC was activated and beaches were closed as
a precaution; no evacuation orders were issued, and no damages occurred.
The National Oceanic and Atmospheric Administration reports one tsunami event in Orange County:23
22 Ethan Miller Brown, OCSD Emergency Management Division, email correspondence, September 5, 2017.
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• September 16-17. 2015. As described above, an 8.3 magnitude earthquake off the coast of Chile
led the National Tsunami Warning Center to issue a tsunami advisory for a portion of California,
including Orange County. All beaches, harbors, piers, and marinas in the Cities of Seal Beach,
Huntington Beach, Newport Beach, Laguna Beach, Dana Point and San Clemente, including
County and State beaches were closed. Tsunami wave heights were observed to be just under one
foot along the Orange County coast. The Orange County EOC reported no significant coastal
flooding, but to be aware of the high likelihood of strong currents and waves dangerous to
persons in or near the water.
3.2.11.3 Location/Geographic Extent
Figure 3-11 illustrates the portions of the planning area within a tsunami hazard zone. Tsunami
inundation maps are provided by the California Geological Survey and represent a combination of the
maximum considered tsunamis for each area.
As illustrated on Figure 3-11, tsunami inundation areas are contained to the coastal areas of the planning
area, extending into areas of Seal Beach, Huntington Beach, Newport Beach, Laguna Beach, Dana Point,
and San Clemente.
3.2.11.4 Magnitude/Severity
The magnitude/severity of a tsunami would be dependent upon the severity and location of the event
causing the tsunami. The California Geological Survey tsunami inundation maps (refer to Figure 3-11)
identify the maximum extent of the tsunami inundation area within the County, which is primarily
contained to the coastline. However, the inundation areas extend into several coastal communities with
the largest potential inundation areas occurring within the cities of Seal Beach, Huntington Beach,
Newport Beach, and Dana Point.
3.2.11.5 Probability of Future Occurrences
The historic record indicates that there is a low probability of occurrence of a major tsunami in Orange
County. However, there is the potential for future tsunami events to impact water and wastewater
infrastructure located within a tsunami inundation area. This probability is similar for each of the
jurisdictions located within these areas.
23 National Oceanic and Atmospheric Administration, National Centers for Environmental Information, Storm Events
Database, Event Types: Tsunami, https://www.ncdc.noaa.gov/stormevents/choosedates.jsp?statefips=6,CALIFORNIA, accessed
March 21, 2018.
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Los Angeles
County
Water Districts Infrastructure
e Reservoirs
• MET Diemer Filtration Plant
• Water Treatment Plant
~ Wastewater Treatment Plant
Potable Local
-MET/Joint Agency Pipe Lines
--Local Sewer Lines
--Regional Sewer Lines
Outfall Lines
------Force Mains
Water Agency Boundary
Figure 3-11
Tsunami Hazard Zones
Tsunami Hazard
Zones
Tsunami Hazard
San Bernardino
County
2.5
ORANGE COUNTY
Risk Assessment
Riverside County
10
~~_L._____.__J
Miles
San Diego County
POTABLE AND WASTEWATER INFRASTRUCTURE
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3.2.12 Wildland/Urban Fire
3.2.12.1 Description (Nature) of the Hazard
A variety of fire protection challenges exist within Orange County, including structure fires, urban fires,
wildland fires, and fires at the wildland/urban interface. This hazard analysis focuses on wildland fires,
but also addresses issues specifically related to the wildland/urban interface. There are three categories of
interface fires: the classic wildland/urban interface exists where well-defined urban and suburban
development presses up against open expanses of wildland areas, the mixed wildland/urban interface is
characterized by isolated homes, subdivisions and small communities situated predominantly in wildland
settings, and the occluded wildland/urban interface existing where islands of wildland vegetation occur
inside a largely urbanized area. Certain conditions must be present for significant interface fires to occur.
The most common conditions include: hot, dry and windy weather, the inability of fire protection forces
to contain or suppress the fire, the occurrence of multiple fires that overwhelm committed resources, and
a large fuel load (dense vegetation). The three primary factors that lead to severe wildfires in Orange
County are drought, insect infestation causing tree decimation (bark beetles), and wildfire suppression.
Once a fire has started, several conditions influence its behavior, including fuel topography, weather,
drought, and development.
A key challenge Orange County faces regarding the wildfire hazard is the increasing number of houses
being built in the wildland/urban interface. Every year the growing population has expanded further and
further into the hills and mountains, including forest lands. The increased "interface" between
urban/suburban areas and open space areas has produced a significant increase in threats to life and
property from fires and has pushed existing fire protection systems beyond original or current design and
capability.
3.2.12.2 History/Past Occurrences
Although no federally-declared wildfire disasters have occurred in Orange County, significant wildfires
have impacted the County and surrounding areas. Since 1950, the National Oceanic and Atmospheric
Administration reports 28 wildfire events occurring with Orange County. Table 3-11, Major Wildfires,
identifies significant fires that have occurred since 1950.
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Date location
8/22/2000 San Clemente
9/11/2000 San Clemente
8/7/2001 Laguna Beach
9/9/2001 El Toro
1/23/2002 Trabuco
5/13/2002 Mission Viejo
2/6-12/2006
Santa Ana Mountains 3/11-14/2007 and Foothills
Santa Ana Mountains 10/21/2007 and Foothills
Final I August 2019
Risk Assessment
Table 3-11
Major Wildfires
Descriptiolll '
Hot temperatures and dry conditions allowed a brush fire to quickly race up hill and
ignite the underside of two roofs. Fifteen families were evacuated as more than 40
firefighters worked for several hours to control the blaze.
A wild fire was fanned by east winds and burned 500 acres before being contained.
A wild fire in a steep canyon near the main toll plaza on the San Joaquin Hills Toll
Road (Highway 73).
A brush fire burned 30 acres before it was brought under control.
Santa Ana winds gusted between 60 to 70 mph for several days across Southwest
California.
Extremely dry conditions, above normal temperatures, and gusty winds, helped a
brush fire, started by an arsonist, to quickly consume 1100 acres before being
controlled. Two trucks and one structure were destroyed. Many residential homes
suffered smoke damage and residents were evacuated. Traffic was halted on
Highway 241. No injuries occurred.
Santa Ana Winds and Red Flag conditions resulted in the rapid spread of a wildfire
in the Santa Ana mountains. Named the Sierra Fire, this fire burned 10,854 acres
from Sierra Peak to the 241 Toll Road. While evacuations were ordered, no
structures were burned. Eight minor injuries were reported.
The Windy Ridge Fire was intentionally set during the early stages of a red flag
event at the mouth of Fremont Canyon. Humidity values less than 10% and wind
gusts in excess of 40 mph caused the fire to spread quite rapidly across the rain
starved hillsides. At the time of the fire, the Santa Ana Fire Station had only
measured 1.81 inches of rain on the season, nearly 9 inches below the average
rainfall for that date. Mandatory evacuations were posted for 1200 homes in
Anaheim Hills and Orange as the wind-driven fire spread westward. The fire
burned 2036 acres, damaged one home, and destroyed two out-structures before it
was extinguished.
The Santiago Fire was intentionally set and burned 28,400 acres in Modjeska and
Santiago Canyons. The fire destroyed 15 homes and 9 outbuildings. An additional
20 structures were damaqed. Sixteen firefiqhters were injured durinq the blaze.
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SECTION THREE
9/23/2010
8/5/2013
Santa Ana Mountains
and Foothills
Santa Ana Mountains
and Foothills
9112 _ 1312014 Santa Ana Mountains
and Foothills
9/25/2017
10/9/2017
Santa Ana Mountains
and Foothills
Orange County Inland
Table 3-11 [continued]
Major Wildfires
Descdption
Risk Assessment
The Long Canyon fire started in the Cleveland National Forest in eastern Orange
County, west of the Ortega Highway near the Riverside County line. Some
structures were threatened, but the fire generally burned away from the populated
areas, 40 acres total. Three firefighters and one police officer suffered non-life-
threatening heat-related and smoke inhalation injuries. One of the Cleveland
National Forest's fire enQines was destroyed by fire, cause unknown, no injuries.
The Falls Fire started off Ortega Highway near Decker Canyon, in Riverside. Due
to the fire burning on the Trabuco Ranger District, the San Mateo Wilderness, El
Carisa Campground, Blue Jay Campground, the Firefighter Memorial Picnic Area
and Wildomar OHV area were closed. Road closures included Ortega Hwy 7 4 from
Lake Elsinore west to San Antonio Parkway. Evacuations were ordered for
Lakeland Village, Rancho Capistrano and Decker Canyon residents. Evacuation
perimeter was between Grand/Ortega and Grand/Corydon. No structures were
threatened and no injuries. Minor guardrail damage occurred because of a rock fall
along Ortega Highway. The fire burned 1416 acres before being fully contained.
The Silverado Fire began along Silverado Canyon Road in the Cleveland National
Forest of the Santa Ana Mountains. The fire burned at a critical rate of spread,
threatening power lines and forcing evacuations and road closures. Mandatory
Evacuations were ordered from 30331 Silverado Canyon east to the end of the road
(fire gate) and included 50 residences affecting approximately 220 people. The
American Red Cross opened an evacuation center at 1530 at El Modena High
School at 3920 East Spring Street. The 12kV line servicing Silverado residents was
down. One pole and the downed lines required replacement. There were 71
customers without power in Silverado Canyon. After burning a total of 1600 acres,
the Silverado Fire was completely contained.
The Canyon fire began near Highway 91 in Orange County. The fire spread rapidly
due to dry fuel conditions and very low humidity, and firefighting efforts were
hindered by a transition from light Santa Ana Winds to onshore flow. This initially
pushed the fire into the foothills before sending it back eastward toward Corona.
The fire was estimated at 1700+ acres and was threatening residences. Winds
calmed over the ensuing days and the fire was quickly contained at 2662 acres.
The cause of the wildfire was determined to be a roadside flare.
The Canyon 2 fire began near the 91 Freeway and Gypsum Canyon Road in
Anaheim Hills. The fire spread rapidly threatening numerous structures. In the first
24 hours the fire consumed more than 7,000 acres. In total, 25 structures were
destroyed, 55 were damaged and 9,217 acres burned. Four injuries were also
reported. The cause of the fire was reported to be embers from the Canyon Fire
which began September 25 and was contained October 4, 2017.
National Oceanic and Atmospheric Administration, National Centers for Environmental Information, Storm Events Database, Event Types:
Wildfire, https://www. ncdc. noaa.Qov/stormevents/choosedates.jsp?statefips=6, CALIFORNIA, accessed March 21, 2018.
Final I August 2019 3-63
SECTION THREE Risk Assessment
At 9:01 am on November 15, 2008 the Corona Fire Department responded to calls reporting a brush-fire
in Riverside County. Upon arrival it became apparent to first responders the fire would be significant and
of a highly destructive nature. At the time of the alarm a Red-Flag Warning had been in effect due to
low-humidity levels, high temperatures, and strong Santa Ana winds. These conditions along with the
terrain of the areas burned facilitated the rapid growth and spread of the fire and significantly affected
first responder's efforts of containment and in the protection of property and lives. Initial calls reported
the fires location as west of the Green River exit off the 91 Freeway in Riverside County. From there the
fire quickly advanced in a Northwesterly direction towards Orange County where the fire split into two
separate branches shortly after crossing over the county line; the first branch of the fire followed the Santa
Ana river basin southwest into Anaheim hills, and the second continued northwest into Yorba Linda.
Both branches of the fire became of concern to the water utilities of Orange County as the fire threatened
infrastructure or moved into the service areas of Anaheim, Brea, the Yorba Linda Water District, and
MET's Diemer Filtration Plant facility. Eventually, the fire burned through approximately 30,305 acres
and damaged or destroyed over 300 structures in Riverside, San Bernardino, Los Angeles, and Orange
Counties.
A brush fire erupted along State Route 241 near Santiago Canyon Road in Irvine on the morning of July
13, 2015. Campgrounds near Irvine Lake were evacuated, and three abandoned structures caught fire.
The blaze encompassed a total of approximately 214 acres. Around one year later, a fire occurred in the
Laguna Coast Wilderness Park near Bommer Ridge Trail on June 26, 2017. The fire burned
approximately 47 acres and was reported as contained on June 27, 2017. On August 31, 2016, the Holy
Fire started in the early morning just east of Trabuco Canyon in the Cleveland National Forest. The blaze
did not threaten any homes; however, it was in an area around Holy Jim Canyon that was difficult for
firefighters to reach. The fire burned through approximately 150 acres.
3.2.12.3 Location/Geographic Extent
Cal Fire prepares fire hazard severity maps including mapping areas of significant fire hazards based on
fuels, terrain, weather, and other relevant factors. These zones, referred to as Fire Hazard Severity Zones
(FHSZ), define the application of various mitigation strategies and influence how people construct
buildings and protect property to reduce risk associated with wildland fires. According to Figure 3-12,
the southern and eastern portions of the County are located within High and Very High Fire Severity
Zones.
3.2.12.4 Magnitude/Severity
California experiences large, destructive wildland fires almost every year and Orange County is no
exception. Wildland fires have occurred within the County, particularly in the fall, ranging from small,
localized fires to disastrous fires covering thousands of acres. The most severe fire protection problem is
wildland fire during Santa Ana wind conditions. These conditions have been further exacerbated by more
recent drought conditions. Drought causes fuels (both live and dead vegetation) to dry out and become
more flammable increasing the probability of ignition along with the rate of fire spread. If drought
continues for an extended period, the number of days with elevated probability of ignition and fire spread
increases, raising the risk of widespread burning. The combination of drought conditions, need to
maintain water fire flow and the potential for power failure due to Santa Ana wind conditions can impact
the magnitude and severity of fires within the planning area.
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SECTION THREE
Los Angeles
County_
Water Districts Infrastructure
• Reservoirs
• MET Diemer Filtration Plant
• Water Treatment Plant
~ wastewater Treatment Plant
Potable Local
Figure 3-12
Fire Hazard Severity Zones
San Bernardino
County
MET/Joint Agency Pipe Lines Fire Hazard
--Local Sewer Lines Severity Zones
--Regional Sewer Lines
outfall Lines
------Force Mains
Water Agency Boundary
Moderate
High
.. Very High 2_5
ORANGE COUNTY
Risk Assessmenl
Riverside County
San Diego County
10
POTABLE AND WASTEWATER INFRASTRUCTURE
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SECTION THREE Risk Assessment
The magnitude/severity of a wildfire would be dependent upon the location and conditions (e.g., Santa
Ana winds) in place at the time. The Fire Hazard Severity Zone maps prepared by Cal Fire (refer to
Figure 3-12) identify the extent and severity of the fire hazard zones within the County. Although a fire
could start and/or extend beyond these areas, they identify the areas of severity so that measures can be
identified to mitigate the rate of spread and reduce the potential intensity of uncontrolled fires that
threaten to destroy resources, life, or property.
3.2.12.5 Probability of Future Occurrences
Wildfires are a regular feature of many of California's ecosystems, and will continue to be in the future.
Since the northern, eastern, and southern portion of the County are considered wildland/urban interface
areas, the County has a higher probability of wildfire risks in those communities and surrounding areas.
The specific chance of wildfire in the County's wildland/urban interface is not known, but the general
vulnerability of the area to fires means that there is a reasonable possibility such an event will occur.
According to the Planning Team and based on conditions experienced within the last several years, the
probability of the County experiencing wildfires is highly likely -near 100% probability in the next year
or happens every year.
3.2.13 Human-Caused Hazards
3.2.13.1 Description (Nature) of the Hazard
Human-caused hazards are distinct from natural hazards in that they result directly from the actions of
people. Two types of human-caused hazards include: non-malicious and malicious. Non-malicious
hazards refer to incidents that can arise from human activities such as the manufacturing, storage,
transport, and use of hazardous materials, which include toxic chemicals, radioactive materials, and
infectious substances. Non-malicious hazards are assumed to be accidental and their consequences
unintended. Malicious, on the other hand, encompasses intentional and criminal acts involving weapons
of mass destruction (WMD) or conventional weapons. WMD can involve the deployment of biological,
chemical, nuclear, and radiological weapons with the result of affecting a significant percentage of the
population either directly or indirectly. Conventional weapons and techniques include the use of arson,
incendiary explosives, armed attacks, intentional hazardous materials release, and cyber-terrorism (attack
via computer). Typically, conventional weapons have a very specific target and are limited in scope and
affect.
Hazardous materials can include toxic chemicals, radioactive materials, infectious substances, and
hazardous wastes. The State of California defines a hazardous material as a substance that is toxic,
ignitable or flammable, or reactive and/or corrosive. An extremely hazardous material is defined as a
substance that shows high acute or chronic toxicity, carcinogenicity, bio-accumulative properties,
persistence in the environment, or is water reactive (California Code of Regulations, Title 22).
"Hazardous waste," a subset of hazardous materials, is material that is to be abandoned, discarded, or
recycled, and includes chemical, radioactive, and bio-hazardous waste (including medical waste). An
accidental hazardous material release can occur wherever hazardous materials are manufactured, stored,
transported, or used. Such releases can affect nearby populations and contaminate critical or sensitive
environmental areas. With respect to water or wastewater systems, concerns arise regarding exposure to
these materials via contact or ingestion of drinking water and or discharge of contaminated water into the
ocean where exposure to the marine environment and public would be of concern.
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NON-MALICIOUS HAZARDS
Non-malicious hazards can occur because of human carelessness, technological failure, and natural
hazards. When caused by natural hazards, these incidents are known as secondary hazards, whereas
intentional acts are terrorism. Hazardous materials releases, depending on the substance involved and
type of release, can directly cause injuries and death and contaminate air, water, and soils. While the
probability of a major release at any facility or at any point along a known transportation corridor is
relatively low, the consequences ofreleases of these materials can be very serious.
The most common sources of contamination to water supply systems are naturally occurring chemicals
and minerals (i.e., arsenic, radon, and uranium), local land use practices (i.e., fertilizers and pesticides),
manufacturing processes, sewer overflows, and malfunctioning wastewater treatment systems (i.e., nearby
septic systems). Although these contaminants present an environmental and human health risk concern,
the EPA holds regulations in place to ensure water supply systems do not contain elevated levels of
contaminants.
Some hazardous materials also present a radiation risk. Radiation is any form of energy propagated as
rays, waves or energetic particles that travel through the air or a material medium. Radioactive materials
(e.g., uranium, plutonium, radium, and thorium) are composed of unstable atoms. An unstable atom gives
off its excess energy until it becomes stable. The energy emitted is radiation. The process by which an
atom changes from an unstable state to a more stable state by emitting radiation is called radioactive
decay or radioactivity.
Radiological materials have many uses including:
• Use by doctors to detect and treat serious diseases,
• Use by educational institutions and companies for research,
• Use by the military to power large ships and submarines, and
• Use as a critical base material to help produce the commercial electrical power that is generated
by a nuclear power plant.
Radioactive materials, if handled improperly, or radiation accidentally released into the environment, can
be dangerous because of the harmful effects of certain types of radiation on the human body and the
human environment. The longer a person is exposed to radiation and the closer the person is to the
radiation source, the greater the risk. Although radiation cannot be detected by the senses, scientists can
easily detect it with sophisticated instruments that can detect even the smallest levels of radiation. Under
extreme circumstances, an accident or intentional explosion involving radiological materials can cause
very serious problems. Consequences may include death, severe health risks to the public, damage to the
environment, and extraordinary loss of, or damage to, property.
TERRORISM
Following several serious international and domestic terrorist incidents since the early 2000s, citizens
across the United States have paid increased attention to the potential for deliberate, harmful terrorist
actions by individuals or groups with political, social, cultural, and religious motives. There is no single,
universally accepted definition of terrorism, and it can be interpreted in a variety of ways. However,
terrorism is defined in the Code of Federal Regulations as " ... the unlawful use of force and violence
against persons or property to intimidate or coerce a government, the civilian population, or any segment
thereof, in furtherance of political or social objectives" (28 CFR, Section 0.85). The Federal Bureau of
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SECTION THREE Risk Assessment
Investigation further characterizes terrorism as either domestic or international, depending on the origin,
base, and objectives of the terrorist organization. However, the origin of the terrorist or person causing
the hazard is far less relevant to mitigation planning than the hazard itself and its consequences.
Terrorists can utilize a wide variety of agents and delivery systems.
Water supplies and infrastructure, such as dams, in Orange County are considered as potential terrorist
targets. The weapon most likely used could include explosives with the goal of collapsing the dam. Such
an event would result in a dam failure and an inundation event with little or no warning. The potential of
using other types of weapons such as chemical or biological are considered low due to the large amount
of material that would be required to contaminate the water system. This scenario would only apply to
those dams where the reservoirs are used for drinking water.
Another very significant concern is cyber terrorism. All of Orange County's water utilities utilize
Supervisory Control and Data Acquisition systems (SCADA), which operate over telecommunication
lines and/or radio systems. These systems are vulnerable to hacking and leave utilities open to malicious
acts.
3.2.13.2 History/Past Occurrences
HAZARDOUS MATERIAL RELEASES
Numerous facilities in Orange County generate hazardous wastes in addition to storing and using large
numbers of hazardous materials. Although the scale is usually small, emergencies involving the release
of these substances can occur daily at both fixed sites and on the County's streets and roadways.
Facilities that use, manufacture, or store hazardous materials in California must comply with several state
and federal regulations. The Superfund Amendments and Reauthorization Act (SARA Title III), which
was enacted in 1986 as a legislative response to airborne releases of methyl isocyanides at Union Carbide
plants in Bhopal, India and in Institute, West Virginia. SARA Title III, also known as the Emergency
Planning and Community-Right-To-Know Act (EPCRA), directs businesses that handle, store or
manufacture hazardous materials in specified amounts to develop emergency response plans and report
releases of toxic chemicals. Additionally, Section 312 of Title III requires businesses to submit an annual
inventory report of hazardous materials to a state-administering utility. The California legislature passed
Assembly Bill 2185 in 1987, incorporating the provisions of SARA Title III into a state program. The
community right-to-know requirements keep communities abreast of the presence and release of
hazardous wastes at individual facilities.
Additional information about the chemicals handled by manufacturing or processing facilities is contained
in the U.S. EPA's Toxic Release Inventory (TRI) database. The TRI is a publicly available EPA database
that contains information on toxic chemical emissions and waste management activities reported by
certain industry groups as well as federal facilities. This inventory was established under EPCRA and
expanded by the Pollution Prevention Act of 1990. Facilities that exceed threshold emissions levels must
report TRI information to the U.S. EPA, the federal enforcement agency for SARA Title III.
Over the past several decades industrial activities have contaminated Orange County's North Basin,
which provides much of the water used in 22 Orange County cities, including parts of Fullerton,
Anaheim, and Placentia. Over five square miles of contaminants, mostly volatile organic compounds
(VOCs), have migrated through the soils and are now leaching into the underlying groundwater. These
VOCs have impacted nearby water supply wells causing four of them to be taken out of service. The
Orange County Water District (OCWD), under EPA oversight, is currently conducting an interim
remedial investigation and feasibility study to determine the extent of groundwater contamination.
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Chemical air em1ss10ns, surface water discharges, underground injections, and releases to land are
considered chemical releases. The release of a biological agent capable of causing illness in people is
considered an infectious release. The only known release of radiological agents into the air in the County
was the result of an accident at San Onofre Nuclear Generating Station (SONGS). In 1981, an accidental
"ignition" of hydrogen gases in a holding tank of the SONGS caused an explosion which bent the bolts of
an inspection hatch on the tank, allowing radioactive gases in the tank to escape into a radioactive waste
room. From there, the radioactive material was released into the atmosphere. The plant was shut down
for several weeks following the event (W.l.S.E. Vol.3 No.4 p.18). This incident occurred during the
plant's operation of its Unit 1 generator, which has since been decommissioned. No serious injuries
occurred.
On February 3, 2001, another accident occurred at SONGS when a circuit breaker fault caused a fire that
resulted in a loss of offsite power. Published reports suggest that rolling blackouts during the same week
in California were partially due to the shutdown of the SONGS reactors in response to the 3-hour fire.
Although no radiation was released, and no nuclear safety issues were involved, the federal Nuclear
Regulatory Commission sent a Special Inspection Team to the plant site to investigate the accident.
In June 2013, SONGs permanently closed after faulty replacement steam generators were installed at the
nuclear facility. SONGS is currently undergoing the process to decontaminate and dismantle the nuclear
facility. As of August 2017, a court settlement requires the operators of SONGS, Southern California
Edison (SCE), to relocate the 3.55 million pounds of nuclear waste to another facility. Among the
possible sites is the Palo Verde Nuclear Generating Station in Arizona, located approximately 330 miles
away. Transportation of nuclear waste poses an environmental and human health risk concern if radiation
is released into the environment.
TERRORISM
While Orange County has not experienced any high-profile attacks by groups or individuals associated
with international terrorist organizations, Orange County has several groups for advisory notification,
investigation, and analysis of terrorist events and activities. These groups include:
• Orange County Joint Terrorism Task Force (OCJTTF): The OCJTFF was formed by the Orange
County Sheriffs Department teamed with the FBI and other local police agencies. The OCJTTF
is one of sixty-six JTTF's across the United States and the 3rd largest in the nation. Team
members are tasked with collecting, analyzing, and sharing critical information and intelligence
involving matters related to any terrorism investigation occurring in or affecting the Orange
County area.
• Orange County Private Sector Terrorism Response Group (PSTRG): The PSTRG was formed in
December 2001 to create a private sector partnership with the Terrorism Early Warning Group to
effectively address private sector safety, incident management, employee education and public
health consequences of potential attacks on the critical infrastructure within Orange County. Two
large groups involved with PSTRG are the Orange County Business Council, of which 80% of
the major businesses in Orange County are members, and TechNet, a consortium of 28 high-tech
firms. The objectives of the PSTRG include physical resource sharing, information exchange,
virtual reach-back capabilities, and subject/industry matter experts cross-utilization. The PSTRG
is an instrument which allows the Sheriffs Department to maximize all resources and prepare
community members for the potential of terrorism and recovery in its aftermath.
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SECTION THREE Risk Assessment
• Orange County Intelligence Assessment Center (OCIAC): The OCIAC was built on the
foundation established by the Orange County Sheriff Department's Terrorism Early Warning
Group (TEWG) from 2001 to 2007 and is an Operational Area asset governed by the Orange
County Chiefs and Sheriffs Association (OCCSA). The OCIAC is a proactive multi-agency,
multi-discipline collaborative which provides comprehensive analysis, intelligence, timely
information sharing, and infrastructure protection. Within the OCIAC, the Critical Infrastructure
Protection Unit uses a multi-disciplinary team comprised of law enforcement, fire, medical, and
private sector experts to conduct vulnerability assessments, provide relevant security updates, and
training resources to our public and private sector partners in a combined effort to protect our
county's assets against terrorist attack, criminal activity, and natural disasters.
• Law Enforcement Mutual Aid: Orange County law enforcement has long recognized the need for
standardization and uniformity of organization and response on the part of public safety providers
involved in major multi-discipline and multi-jurisdictional incidents. The collaborative efforts of
Orange County law enforcement leaders over the past 53 years have forged a collective voice in
mutual assistance and mutual aid. All major components tasked with public safety (law, fire,
health, emergency management) are actively involved in developing emergency plans and
insuring emergency preparedness.
3.2.13.3 Location/Geographic Extent
Human-caused hazards may affect a specific location or multiple locations, each of which may be a
disaster scene, a hazardous scene, and/or a crime scene simultaneously. An accidental hazardous
materials release can occur wherever hazardous materials are manufactured, stored, transported, or used.
In Orange County, a hazardous material event is most likely to occur within the County's industrial areas.
One of the special considerations in dealing with the terrorist threat is that it is difficult to predict. The
Department of Homeland Security's National Planning Scenario identifies the possible terrorist strike
locations it views as most plausible; places at risk include cities that have economic and symbolic value,
places with hazardous facilities, and areas where large groups of people congregate, such as an office
building, sports arena, or amusement park. As such, Anaheim (Disneyland, Angels Stadium, Honda
Center), Buena Park (Knott's Berry Farm), and San Clemente (SONGS) are viewed as potential targets.
3.2.13.4 Magnitude/Severity
Human-caused hazards have the potential to directly impact water and wastewater systems. A hazardous
material spill could be localized and depending upon when the spill is identified and addressed, may be
contained with limited to no impact on water supplies and systems. However, there is the potential for a
hazardous material spill to severely impact water supplies due to groundwater intrusion and direct
contamination of a water source. The magnitude and severity of the hazard would be highly dependent
upon the type of hazardous material spill, location, and the extent to which the hazardous material extends
into the water system. Similarly, an act of terrorism could cause a significant impact to water and
wastewater systems depending upon the type of event and whether it occurs at a primary source or is
focused to a specific area or system. Human-caused hazards can have a direct impact on water supplies
and the ability to provide water services to communities, potentially resulting in significant health and
safety issues.
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3.2.13.5 Probability of Future Occurrences
According to the Governor's Office of Emergency Services, hazardous materials have been released
approximately 250 times to the environment between the years of 2006 and 2017 in Orange County.
Thus, the probability of future contamination to the environment is likely. However, human consumption
of contaminated groundwater is unlikely due to the constant monitoring of over 700 wells across Orange
County.24
Because of the dynamic nature of the terrorist threat and the open nature of California society, all
jurisdictions within California are vulnerable to terrorist attack. One must know the minds and
capabilities of various terrorists and terrorist groups; these are characteristics terrorist organizations strive
to conceal. Because all terrorists are not the same, the calculation is even more difficult. From the
perspective of hazard mitigation, the most often used weapon of terrorists is bombs and the greatest
potential for loss is from WMDs.
3.2.14 Power Outage
3.2.14.1 Description (Nature) of the Hazard
A power outage typically occurs during a natural hazard such as extreme weather conditions, earthquakes,
flood, fire or severe winds. An outage can result in damaged power equipment or equipment failures and
can affect multiple counties for hours. This type of event can range from a moderate event to a
catastrophic regional event that may threaten human life, safety, and health, or interferences with vital
services. An outage may occur as a secondary effect of another hazard, or as the result of construction, an
accident, or terrorism. Severe winds and flood can bring down trees and tree limbs onto power lines.
And these types of events can cause serious safety hazards to the public and emergency responders.
3.2.14.2 History/Past Occurrences
Orange County has experienced many power outages in the past. There have been small to moderate
incidents, and several extreme incidents that have lasted hours in certain areas. Power outages are most
commonly seen in Southern California when Santa Ana wind conditions occur.
One of the most severe events, referred to as the 2011 Southwest Blackout, took place in September 2011.
This event affected southern Orange County, San Diego-Tijuana area, Imperial Valley, Mexicali Valley,
Coachella Valley, and parts of Arizona. The incident is known to have been an 11-minute system
disturbance which led to cascading outages and 2. 7 million customers left without power, some for up to
12 hours. The hardest hit areas of San Diego-Tijuana, experienced street gridlock due to loss of traffic
signals, school and businesses closing, flights and public transportation delays, and water and sewage
pumping station power loss.
In 2013, a blackout resulted in approximately 123,000 homes and businesses losing power for several
hours. Faulty circuits affected people in a number of Orange County communities including Mission
Viejo, Laguna Niguel, Ladera Ranch, Coto De Caza, Ortega, San Clemente, Talega, San Juan Capistrano,
Dana Point, and Capistrano Beach.
24 Orange County Water District Groundwater Management Plan, 2015 Update, June 17, 2015.
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3.2.14.3 Location/Geographic Extent
A power outage can cause impacts at the local level and potentially the regional level. As seen from
previous occurrences, a severe outage can easily impact several counties at a time. All jurisdictions
within the planning area have the potential to be impacted should an event occur; either directly or
indirectly. Highly developed communities may see more outage occurrences if a heat wave should occur,
due to the number of cooling systems running at once. Water and wastewater facilities with backup
generators or alternate power sources are less likely to experience severe losses or disruption.
3.2.14.4 Magnitude/Severity
A power outage has the potential to directly impact water and wastewater systems. Disruption of water
utilities and systems often requires notification of the public and businesses to curtail usage, boil available
water, use bottled water, etc. Firefighting capabilities may also be impacted if an outage causes
disruption to water supplies. In areas where telephone service is provided by above-ground lines that
share poles with electrical distribution lines, telecommunications providers may not be able to make
repairs to the telephone system until electrical utilities restore power lines to a safe condition. This could
impact response times to a water or wastewater incident. The impacts of electric utility disruptions are
felt most significantly by southern California communities during the summer months due to cooling
demands from higher heat. Any extended electric disruption can also lead to local economic losses when
computers, lighting, refrigeration, gas pumps, and other equipment are without power during business
hours. A severe power outage also can cause cascading impacts such as transportation incidents, civil
unrest, and disease. The magnitude/severity of a power outage would be the same for all jurisdictions
within the planning area.
3.2.14.5 Probability of Future Occurrences
Power outages are a normal part of life and are unpredictable; they happen for many reasons and can be
expected to continue in the future. Water and wastewater systems are most susceptible to failure during
extreme weather conditions, fires, and earthquake events. Regional power outages can threaten human
life, particularly when outages affect water supply, hospitals, and other healthcare facilities. As both
population and climate variability increase across southern California, and put more pressure on aging
distribution systems, it is likely that power outage events will continue to occur. Due to the nature and
extent of power outages, the probability for future occurrences would be the same for all jurisdictions in
the planning area.
3.3 VULNERABILITY ASSESSMENT
Vulnerability describes how exposed or susceptible to damage an asset is, and depends on an asset's
construction, condition, contents and the economic value of its functions. A vulnerability analysis
predicts the extent of injury and damage on the existing and future built environment that may result from
a hazard event of a given intensity in a given area. Due to the interrelatedness of water and wastewater
infrastructure and the role each have in public health and safety, vulnerabilities in one community are
often related to vulnerabilities in another. Indirect effects can be much more widespread and damaging
than direct effects. For example, damage to a major water utility line could result in significant
inconveniences and business disruption that would far exceed the cost of repairing the utility line.
Final I August 2019 3-72
SECTION THREE Risk Assessment
The vulnerability assessment quantifies, to the extent feasible using best available data, assets at risk to
hazards and estimates potential losses. This section focuses on the risks to the planning area; data for
each of the MAs was also evaluated and is included here and in the Jurisdictional Annexes.
3.3.1 Asset Inventory
Hazards that occur in Orange County can impact critical facilities located throughout the County. For this
Plan update, a critical facility is defined as public infrastructure used to provide potable water to the
public and maintain wastewater services, necessary to maintain public health and safety. Critical facilities
associated with potable water services located within the planning area include: wells, water storage
tanks, reservoirs with dams, water treatment plants, pump stations, pressure reducing stations, emergency
interties, service connections, pipelines, and administrative buildings and utility yards; refer to Table 3-
11., Summary Assets, at the end of this section. Critical facilities associated with wastewater services
located within the planning area include: wastewater treatment plants, lift stations, pipelines, and
administrative buildings and utility yards (Table 3-13 ).
3.3.2 Estimating Potential Exposure and Losses
Orange County covers 948 square miles with several different climate patterns and types of terrain, from
the coast to the mountains, which allows for several hazards to affect various parts of the County, as
described above. Due to the vast area, a hazard event could impact a single jurisdiction or multiple
jurisdictions.
Updated mapping of water and wastewater infrastructure was prepared in anticipation of the Plan update.
As part of the Plan update, the infrastructure mapping was overlaid with hazards having a physical
geographic location to estimate exposure to water and wastewater infrastructure. Hazard areas and
infrastructure overlays were conducted for wildfires, flooding, fault rupture, earthquakes, liquefaction,
landslides, and tsunamis; refer also to the Jurisdictional Annexes. Hazards and infrastructure overlays
were not conducted for the remaining hazards because data for these hazards was either not available or is
not geographically distinct. Many of these hazards, such as drought, power outage, and high winds/Santa
Ana winds affect the entire planning area; therefore, all water and wastewater infrastructure could be
potentially susceptible to damage from them. For these hazards, quantitative analyses were not
performed. Vulnerability assessments associated with these hazards is based on historic incidents and the
knowledge that water and wastewater experts have of their critical facilities and the susceptibility of those
facilities to these hazards.
For water and wastewater infrastructure pipelines, the length of exposure/impact is given in miles. Other
critical facilities are identified by facility/structure type. Exposure characterizes the value of
facilities/structures within the hazard zone and is shown as estimated exposure based on the overlay of the
hazard on the critical facilities which are assigned a cost of replacement for each type of facility/structure
exposed. These replacement costs for the critical facilities were identified by each MA. The loss or
exposure value is then determined with the assumption that the given facility/structure is destroyed (worst
case scenario), which is not always the case in hazard events. This assumption was valuable in the
planning process, so that the total potential damage value was identified when determining capabilities
and mitigation measures for each MA.
Table 3-12, Unit Replacement Costs o(Facilities, provides average replacement costs used for critical
facilities and infrastructure listed in all subsequent exposure/loss tables.
Final I August 2019 3-73
SECTION THREE Risk Assessment
Table 3-13 provides the total inventory for the critical facilities and infrastructure by jurisdiction.
Estimated exposure for critical infrastructure by MA is provided in the Jurisdiction Annexes. Table 3-14,
Planning Area Critical Facilities and Infrastructure Exposure Costs by Hazard, provides a summary of
exposure for the planning area by hazard. The costs identified reflect cost of replacement in a worst-case
scenario (defined as the highest cost submitted from among all the MAs in the study process, excluding
the regional facilities, as this would overstate the local costs). For example, Garden Grove may have
identified a cost of $3 million to replace a well and Buena Park may identify a cost of $3.5 million to
replace a well; however, $3.5 million would be used as the replacement cost for all wells within the
planning area. This methodology was used for consistency across the planning area and selection of the
highest cost helps assure that appropriate costs are considered when requesting grants. For any detailed
proposals submitted to FEMA, actual costs for mitigation and detailed estimates of the benefits of the
mitigation measure will be prepared and submitted. The costs included herein provide a relative measure
of the impacts of the various hazards.
Table 3-12
Unit Replacement Costs of Facilities $1,000' s(t)
..-:.e1w.tdCest ~')J"'8 i
... ,, ($t,llf$)
. . .
WST Water Storage Tank $20,000
RES Reservoir (with a dam) $50,000
WTP Water Treatment Plant (Diemer Filtration Plant) $350,000
WTP Water Treatment Plant by retail agency $10,000
PS Pump Station (South County Pump Station) $35,000
PS Retail Water Agency Pump Station $8,000
PRS Pressure Reducing Station (MET facility) $52,000
PRS Pressure Reducing Station for retail agency $2,000
EIT Emergency I nterties $2,000
SC Service Connector $3,000
ADM Administration (large administration building) $8,000
LS Wastewater Pump Station/Lift Station by OCSD/SOCWA $4,000
LS Wastewater Pump Station/Lift Station by retail agency $5,000
WWTP Wastewater Water Treatment Plant $30,000
WELL Well $5,000
pp Power Plant (MET Yorba Linda Power Plant) $12,000
(1l Based on the highest cost for typical facility from among the MAs' facility values submitted. These results are
conservatively hiqh replacement costs for some retail aqencies.
For additional detail on exposure of facilities by MA, refer to the Jurisdictional Annexes. The
Jurisdiction Annexes include a discussion of hazards and vulnerabilities specific to each MA, a discussion
of their capabilities to address these losses, and identifies the actions to help mitigate damage to their
infrastructure against hazards identified in the risk assessment.
3.3.3 Land Use and Development Trends/Changes in Development
The MAs provide water and wastewater services to majority of the County, which has a population of
almost 3.2 million people. Depending upon the hazard and its magnitude and duration, a considerable
Final I August 2019 3-74
SECTION THREE Risk Assessment
number of people and businesses could be impacted. Of primary concern would be a hazard that results
in the loss of water supply and wastewater services to the planning area. As discussed previously, a
hazard could result in direct physical damage to water/wastewater infrastructure, as well as indirect
damage resulting from business disruption.
Although Orange County is urbanized and predominately built out, the Southern California Association
of Governments (SCAG) projects continued population, employment, and housing growth into 2040. The
County of Orange and its incorporated cities maintain General Plans, which identify the planned growth
and development for their respective jurisdictions. The planning area includes a wide variety of
residential and non-residential land uses. Water and wastewater service providers will continue to work
with the communities they serve to identify service needs, including the construction, expansion, or
modification of water and wastewater infrastructure. The construction of new facilities or infrastructure
will be completed in coordination with these communities to ensure compliance with appropriate codes
and regulations, including consideration of potential hazards.
Population growth and development in the County has increased smce 2012. According to the
Department of Finance, the population for the County was 3,083,962 in 2012. As of January 1, 2018, the
population is 3,221,103, a growth of 4.4 percent since 2012. Along with population growth has come an
increase in development, increasing demands on water and wastewater infrastructure. Many Orange
County cities have seen shifts in development toward higher-density residential and mixed-use
development projects in response to the demand for housing.
Due to the highly developed nature of the County along with the presence of natural hazards throughout
the area such as earthquakes, liquefaction, flood risk, and wildfires, development and population growth
has continued to occur within areas of risk. Recent drought conditions have placed greater emphasis on
the ability for new development to be served by water supplies and planning for prolonged drought
conditions. Water and wastewater agencies continue to coordinate with the County, cities, and each other
to meet the demands of the respective communities they serve while also strengthening regional and local
infrastructure and overall reliability in the event of a hazard. Agencies and the District have modified
their infrastructure to include EOC's and water infrastructure, to mitigate potential threats.
3.3.4 Vulnerable Populations
Water supplies for safe drinking, sanitation, and hygiene are relied upon by the entire population.
However, there are populations within the MA service areas that would be considered more vulnerable in
the event of a hazard that affects water and wastewater infrastructure. These populations include those
that are reliant on others for their wellbeing, such as young children, individuals with disabilities,
individuals' dependent on medical equipment, and individuals with impaired mobility, as well as people
with low socioeconomic levels. Vulnerable populations are more significantly impacted in the event of a
hazard.
Final I August 2019 3-75
SECTION THREE Risk Assessment
3.4 SUMMARY OF VULNERABILITY
Due to the nature of water and wastewater infrastructure and its location throughout Orange County, there
is some form of infrastructure that intersects with a hazard area. Table 3-14 identifies the infrastructure
that intersects with hazards that have a specific geographic area (e.g., fire hazard, liquefaction, etc.);
however, the entire MA service area also intersects with hazards that are not geographically specific (e.g.,
drought, power outage). The variety of hazards and the varying magnitude and probability of occurrence
make it challenging to assess the hazards that pose the greatest risk to the MAs. The potential losses vary
greatly depending upon the hazard and resulting impact to infrastructure. The challenge is further
magnified by the potential health and economic impacts that could occur in the event water supplies are
disrupted.
Final I August 2019 3-76
SECTION FOUR Risk AllllSIABll
TableJ-13
Summary Assets
.; . : :
.•.. j •.• ,: ··-·, ~' i I ; ,I l',Jl:~·111 :1·' :' ·l!!···-·,·. J !_·· .• · __ ·,·.·.:.,.1 .....•..•. 1_:1 .. i:_:····.·.•.·r!_·,· .• ·.· '1!·'·-· .. •-•.·;_.·.· •. •.: .• · .··.··.·1·_1:.-_-.;_•.~!,t.i_•_.I .. ·.·.•.• ':t
·:• ::·. ., ', j(. It ,1 ,· ··~ ,l, .I .I :i II, f.· ... ···:• .. : .. •, ....... ·.·.· __ .. -.·.; .. ,·_·: .. , ·._I.·.·.· .. • •• ·.'.:_·.·!·:•,.'.-. ti·.•_,_:····:;··l!I•_'_._'' ·1 ::!.· .. ·. ·.i . ·1"5 ·-,···,,_·· ... ·.1'. ",...:91!·······:·•-.-ll!_e'·,.· ll : ;I! p; -'i ~ ,. , .. .. .. . ! . t .... . i ~ . i:ii. , , !. ~ · L :1· 1 I j ! . i• 11 y: ; 1 I ~>H ·
L..._ ___ ...... _ ....... ··'.,.·· ·mi .. --... ~···· ..... ~~ '"'-'-iii1i.o+""".i~~1 ..lil.l...., .. ~""4'·:11~,.....,. ... :1 .... ~1 .·.•-11i._.:'.•.-.·.•ijl..:,. · .. ·• _._·ii; .• 1.·.. ......_·~·,., :.""'l...l.ai...+ 11_: i.·...,t~-......_·+;liloo&11-· .. ·iio0ii·.''.<:i-=l'wi''ii1o'.,_! .... "~ • .:•··+1 ... ·: ... :..""l.1 .... r:.1; -..... ;""i (il;ol. • .... ~.&:~! .. ~.·"""""...,. . ,.... ·•~ _ -:J• '~ .. ·~ "!• , _.a; J "" ~:... . •z Y .., .,, . .,;l:.,."J sr "I
Metropolitan Water District of Orange County 0 0 0 0 3 0 0 0
Orange County Water District 901 27 15 12 40 2
Orange County Sanitation District 753 19
South Orange County Wastewater Authority ' 0 25
Buena Park 225 13 2,362 19,481 165 18,900
El Toro Water District 168 19 12 1,900 9,871 114 8,950 11
Garden Grove 13 440 2 3,959 33,725 330 33,725
La Habra 143 49 18 1,807 13,703 125 13,703
Laguna Beach County Water District 135 21 11 19 14 893 8,488 0
Mesa Water District 317 2 3 15 3,404 24,435 10
Moulton Niguel Water District 655 28 23 16 16 7,154 55,048 501 52,259 17 10
Newport Beach 297 42 13 2,634 26,800 323 5,525 21 0
Orange 15 450 16 16 14 16 4,411 34,000 1
Santa Margarita Water District 626 34 21 25 22 4,250 54,254 630 57,537 19 22 21 25 20
Serrano Water District 43 370 2,350 0 0 0
South Coast Water District 185 13 25 19 1,522 12,551 151 16,500 14
T rabuco Canyon Water District 65 8 12 600 4,000 47 3,600
Westminster 10 230 4 2,672 20,515
Yorba Linda Water District 11 352 14 12 42 10 3,981 24,998 313 23,421 10 10
Joint Water Systems' 94 0 0 10 0
Metropolitan 122
111 Regional water systems identified here are co-owned and managed by multiple utillties
F1na11August2019 3-77
SECTllN THREE
Fire Hazard
Zone
FEMAFlood
Moderate
High
Very High
100-Year
Zone 500-Year
Alquist-Priolo Fault Zone
Ground
Shaking
Liquefaction
Landslide Zone
Tsunami Zone
Moderate
High
Extreme
Moderate
High
Very High
Unknown
14
24
18
22
97
24
13
25
13
Risk Assessment
Table 3-14
Planning Area Critical Facilities and Infrastructure Exposure Costs by Hazard
13 13 0.5
13 1.0
47 10 71 1.6
7 15 0.5
11 35 2.1
0
31 50
60 19 55 57 5.2
25 10 42 26
11 3 14 33
17 40
0
7
18 28 2.8
0.6
111 Based on the highest cost for typical facility from among the MAs' facility values submitted. These results are conservatively high replacement costs for some retail agencies.
Firia11August2019 3-78
If~
Cillls
"llatllile •!'t:e.;:r (S•lllilllan)I
•lliplhe
~· -~
45.02 37.78 1,483.40
59.03 65.8 1,729.64
151.14 100.65 6,098.12
38.73 82.84 1,832.56
106.05 171.96 2,972.88
4.29 0.71 44.0
86.18 52.99 3,917.36
370.53 513.72 11,039.60
169.53 213.85 5,615.04
85.53 188.64 3,219.36
91.48 198.47 3,538.60
10.39 16.74 231.04
54.45 100.4 1,420.80
40.83 42.34 2,276.76
6.75 7.42 163.16
SECTION FOUR Mitigation Strategy
SECTION 4 MITIGATION STRATEGY
Planning is the cornerstone to successful hazard mitigation efforts. Citizens, local government, and
private interests with proactive policies can reduce damages and impacts associated with natural and
human-caused hazards. Benefits realized by implementing hazard mitigation measures include:
• Saving lives by removing people from hazard prone situations.
• Limiting property damage by regulating development in hazard areas.
• Reducing economic impacts by minimizing outages of essential services during and after these
events.
• Saving money for taxpayers by reducing the need for services during a disaster.
• Speeding disaster recovery and post-disaster relief funds.
• Demonstrating a strong commitment to the health and safety of the community.
Relocating people, institutions, and businesses from hazard prone areas saves property and lives.
Removal or protection of the structures means that there is less to pay for disaster recovery or for services
during an event. Having alternative service plans for essential services, such as water, protects structures
from fire and allows residents and businesses to continue functioning or to restore normal functions
quicker following a disaster. Post-event, recovery crews will have less to do because there will be less
damage. Implementation of these measures speeds the overall recovery process.
4.1 HAZARD MITIGATION OVERVIEW
The mitigation strategy and actions were developed by the Planning Team based upon in-depth review of
the vulnerabilities and capabilities described in the Plan. The mitigation actions described in the
Jurisdictional Annexes represent each MA's risk-based approach for reducing and/or eliminating the
potential losses as identified in Section 3 .0, Risk Assessment.
As part of the Plan update process, the hazard mitigation goals were reviewed and refined. It was
determined that the overarching mitigation goals were the same for all MAs. Therefore, one set of goals
were identified for the Plan, as discussed below. If additional, jurisdiction-specific goals were identified
by a MA, they are included in the Jurisdictional Annex.
MAs provided a comprehensive review of their mitigation actions to assess their ability to reduce risk and
vulnerability to the jurisdiction from identified hazards. Upon review of each mitigation action, an
assessment was made as to whether the mitigation action should be carried forward into the Plan update
and/or be revised/modified or removed to reflect changing conditions or priorities. Mitigation actions that
were deemed complete during the current plan period were identified and removed (refer to the
Jurisdictional Annexes). New mitigation measures were also identified.
4.1.1 FEMA's National Flood Insurance Program
In 1968, the U.S. Congress created the National Flood Insurance Program (NFIP) to provide affordable
insurance to property owners while also encouraging communities to adopt and enforce floodplain
management regulations. Community participation is voluntary; however, it is required to receive certain
grants and funding from FEMA. The Orange County Flood Division (OC Flood) is a participant in the
program and administers the floodplains within the unincorporated areas of the County. Within the
incorporated areas, Orange County cities administer their floodplains. Since the creation of NFIP, OC
Flood has worked cooperatively with cities in Orange County to reduce the floodplain area by
Final I August 2019 4-1
SECTION FOUR MiliUlliOI SlrlllUV
constructing flood control facilities that provide 100-year flood protection. Such facilities typically
traverse through the cities and ultimately outlet into the Pacific Ocean. All cities within Orange County
are participants in the program.
REPETITIVE LOSS PROPERTIES
According to the National Flood Insurance Program (NFIP), a repetitive loss structure is an insured
building that has had two or more losses of at least $1,000 each being paid under the NFIP within any 10-
year period since 1978. Each MA has had zero such losses within the water utility, the water department,
or wastewater department.
4.2 HAZARD MITIGATION GOALS
Mitigation goals are defined as general guidelines explaining what each jurisdiction wants to achieve in
terms of hazard and loss prevention. Goal statements are typically long-range, policy-oriented statements
representing jurisdiction-wide visions. The goals and objectives identified in the previous plan were
reviewed by the Planning Team. Through the Plan update process, it was determined that many of the
goals identified for each MA were the similar. As a result, the following hazard mitigation goals have
been identified for the Plan:
Goal 1: Minimize vulnerabilities of critical facilities and infrastructure to minimize damages and
loss of life and injury to human life caused by hazards.
Goal 2: Minimize security risks to water and wastewater infrastructure.
Goal 3: Minimize interruption to water and wastewater utilities.
Goal 4: Improve public outreach, awareness, education, and preparedness for hazards in order to
increase the community resilience.
Goal 5: Eliminate or minimize wastewater spills and overflows (Wastewater agencies).
Goal 6: Protect water quality and supply, critical aquatic resources and habitat to ensure a safe
water supply.
Goal 7: Strengthen Emergency Response Services to insure preparedness, response, and recovery
during any major or multi-hazard event.
The Plan goals guide the direction of future activities aimed at reducing risk and preventing loss from
natural and human-caused hazards. The goals also serve as checkpoints as the MAs begin implementing
mitigation action items. Mitigation goals do not account for implementation cost, schedule, funding
sources, etc. Goals represent what each MA wants to achieve, whereas the mitigation actions provide the
actions to needed to achieve the goals.
4.3 IDENTIFY AND PRIORITIZE MITIGATION ACTIONS
Mitigation actions were identified, evaluated, and prioritized by the MAs. They provide a list of activities
that the MAs will use to reduce their risk of potential hazards. Some of these actions may be eligible for
funding through federal and state grant programs and other funding sources as made available by the MAs
Final I August 2019 4-2
SECTION FOUR Mitigation Strateuv
or other agencies/organizations. The mitigation actions are intended to address the comprehensive range
of identified hazards for each MA; some actions may address risk reduction from multiple hazards.
A detailed list of mitigation actions for each MA is provided in the Jurisdictional Annexes. The process
used by the Planning Team to identify hazard mitigation actions for this Plan included the following:
• Review of the Risk Assessment presented in Section 3.0;
• Review of the Capabilities Assessment presented for each MA in the Jurisdictional Annexes; and
• Team discussion of new concerns/issues that need to be addressed to reduced hazards to critical
water/wastewater infrastructure.
The mitigation actions identify the hazard, proposed mitigation action, location/facility, local planning
mechanism, risk, cost, timeframe, possible funding sources, status, and status rationale, as applicable.
MAs conducted a capabilities assessment (provided in the Jurisdictional Annexes), to identify existing
local agencies, personnel, planning tools, public policy and programs, technology, and funds that have the
capability to support hazard mitigation activities and strategies outlined in this Plan. To identify the
capabilities, the Planning Team collaborated to identify current local capabilities and mechanisms
available for reducing damage from future hazard events. The capabilities and resources were reviewed
while developing the Plan update. After completion of the capabilities assessment, each jurisdiction
evaluated and prioritized their proposed mitigations.
FEMA's STAPLEE technique was used to identify, evaluate, and prioritize mitigation actions based on
existing local conditions. Using this method each MA considered the Social, Technical, Administrative,
Political, Legal, Economic, and Environmental (ST APLEE) opportunities and constraints of
implementing a mitigation action; refer to Table 4-1, STAPLEE Review and Selection Criteria. This
process was used to help ensure that the most equitable and feasible actions would be undertaken based
on each MA' s unique capabilities.
In some instances, MAs revised the priorities of mitigation actions or removed mitigation actions all
together. If the mitigation action was completed and no further action would be needed, the action was
removed. However, in some instances it was determined that a mitigation action was no longer relevant
due to technical changes or advances, a change in service conditions, or the cost associated with a
mitigation that would not result in the benefits needed. Some actions that may have been considered
lower in priority during the last plan update were elevated due to conditions that either allowed for the
action to be prioritized, such as the potential for funding or completion of other mitigation actions that
preceded them. Mitigation actions were also prioritized based on more recent experiences associated with
drought conditions and wildfires. These hazards and the impact they have had throughout Orange County
and the State have resulted in new requirements in how these hazards are addressed in water supply and
water and wastewater infrastructure systems.
4.3.1 Hazard Mitigation Benefit-Cost Review
FEMA requires local governments/agencies to analyze the benefits and costs of a range of mitigation
actions that can reduce the effects of each hazard within their communities. Benefit-cost analysis is used
in hazard mitigation to show if the benefits to life and property protected through mitigation efforts
exceed the cost of the mitigation activity. Conducting benefit-cost analysis for a mitigation activity can
assist communities in determining whether a project is worth undertaking now to avoid disaster-related
damages later. The analysis is based on calculating the frequency and severity of a hazard, avoided future
damages, and risk.
Final I August 2019 4-3
SECTION FOUR MiliUalion Slra1euv
A hazard mitigation plan must demonstrate that a process was employed which emphasized a review of
benefits and costs when prioritizing the mitigation actions. The benefit-cost review must be
comprehensive to the extent that it can evaluate the monetary as well as the nonmonetary benefits and
costs associated with each action. The benefit-cost review should at least consider the following
questions:
• How many people will benefit from the action?
• How large an area is impacted?
• How critical are the facilities that benefit from the action (e.g., which is more beneficial to
protect, the fire station or the administrative building)?
• Environmentally, does it make sense to do this project for the overall community?
Final I August 2019 4-4
SECTION FOUR Mitigation Strategy
Table 4-1
ST APLEE Review and Selection Criteria
STAPLBE Review Selection Criteria
• Is the proposed action socially acceptable to the jurisdiction and surrounding
community?
Social • Any equity issues involved that would mean that one segment of the jurisdiction
and/or community is treated unfairly?
• Will the action cause social disruption?
• Will the proposed action work?
Technical • Will it create more problems than it solves?
• Does it solve a problem or only a symptom?
• Is it the most useful action in light of other jurisdiction goals?
• Can the jurisdiction implement the action?
Administrative • Is there someone to coordinate and lead the effort?
• Is there sufficient funding, staff, and technical support available?
• Are there onqoinq administrative requirements that need to be met?
Political • Is the action politically acceptable?
• Is there public support both to implement and to maintain the project?
• Is the jurisdiction authorized to implement the proposed action?
Legal • Are there legal side effects? Could the activity be construed as a taking?
• Will the jurisdiction be liable for action or lack of action?
• Will the activity be challenqed?
• What are the costs and benefits of this action?
• Do the benefits exceed the costs?
• Are initial, maintenance, and administrative costs taken into account?
• Has funding been secured for the proposed action? If not, what are the potential
Economic funding sources (public, nonprofit, and private)?
• How will this action affect the fiscal capability of the jurisdiction?
• What burden will this action place on the tax base or local economy?
• What are the budget and revenue effects of this activity?
• Does the action contribute to other jurisdiction goals?
• What benefits will the action provide?
• How will the action affect the environment?
Environmental • Will the action need environmental regulatory approvals?
• Will it meet local and state regulatory requirements?
• Are endangered or threatened species likely to be affected?
Final I August 2019 4-5
SECTION FOUR Mitigation Strateuv
These questions were used to help determine the appropriateness of mitigation actions. Benefits and costs
are a primary motivation for implementing mitigation projects at water and wastewater utilities. Past
disasters have shown the benefit-cost of mitigating water utilities against identifiable hazards. For
example, a cold weather system that impacted most of the United States resulted in pipeline breaks across
the State of California. Those ruptures primarily occurred on a specific type of pipeline that has been
gradually phased out of use in California. The replacement of this type of pipeline prior to the cold front
could have not only prevented the cost of pipeline breaks, but also costs related to flooding, landslides,
loss of water supply, other secondary effects of the broken pipelines.
A study conducted in 2003 by the Orange County Business Council found that a 10-day 80% reduction in
water to South Orange County would result in a fiscal impact of $293 million dollars to both businesses
and residents alike. Longer outages during many disaster situations are probable and would be
proportionally more devastating. Each affected agency would share in the economic impacts based on its
mix of business and residential customers.
The final prioritization completed by each MA depended on the direct loss estimations for
water/wastewater critical infrastructure along with the secondary costs associated with business loss and
recovery. Much of this effort was completed with informal cost-benefit analysis based on the knowledge
and expertise of the participants (many of them certified operators, water quality experts, or engineers),
previous planning documents, and the concepts identified above. Those actions that did not have
adequate benefits were excluded from the list of mitigation actions.
4.4 REGIONAL CONSIDERATIONS
It is envisioned that the mitigation actions for the most part will be implemented on a jurisdiction-by-
jurisdiction basis. MWDOC will provide facilitation, as appropriate, of this process to help reduce
duplication of efforts between jurisdictions and to spearhead coordination of initiatives and action items
that could be accomplished more efficiently on a regional level. In its role as a regional planning agency,
MWDOC will act as lead on water related hazard mitigation projects that are regional in nature, such as
projects that cross several jurisdictional boundaries and work planned on behalf of Metropolitan. OCSD
and SOCW A will take the lead on wastewater related hazard mitigation projects that are regional in
nature and within their individual service areas.
The Risk Assessment (Section 3.0) and Jurisdictional Annexes indicate that each MA is susceptible to a
variety of potentially serious hazards in the region. The approach to emergency planning in California
has been comprehensive in its planning for and preparedness to respond to all hazards utilizing the
Standardized Emergency Management System (SEMS) and a coordinated Incident Command System. A
program managed by MWDOC, the Water Emergency Response Organization of Orange County
(WEROC), acts as coordination point (Area Command) to support an effective emergency response to
major disasters by the Orange County water and wastewater utilities. WEROC provides services that
promote planning and preparedness activities for both the utilities, as well as its own Emergency
Operations Center (EOC) staff. WEROC also helps maintain two tum-key EOCs. WEROC receives
guidance from a steering committee, which includes representatives from Orange County water utilities,
Metropolitan, the County of Orange and the California Department of Health Service's Office of
Drinking Water. WEROC and its steering committee help ensure water and wastewater utilities remain
current with state and national emergency response procedures and plans for potential disasters.
The Disaster Mitigation Act of 2000 requires that in addition to having emergency response and
emergency preparedness documents, regions should develop and maintain a document outlining measures
Final I August 2019 4-6
SECTION FOUR Miligalion s1ra1e1v
that can be implemented before a hazard event occurs that would help minimize the damage to life and
property. MWDOC has accepted the role of coordinating the development the Hazard Mitigation Plan as
a multi-jurisdictional plan.
All hazard mitigation planning efforts within the region are the responsibility of the jurisdictions. As
noted, the capabilities of the jurisdictions to perform hazard mitigation planning are detailed in the
Jurisdictional Annexes.
4.4.1 Regional Fiscal Resources
One of MWDOC's primary roles in coordinating the development of the Plan is to identify and obtain
grant funding for preparing and implementing certain aspects of the Plan. This is consistent with
WEROC's role, as a program managed by MWDOC, for hazard mitigation and preparedness. WEROC
has received grants to improve the Emergency Operations Centers and to secure water trailers for
distribution of drinking water during disasters and will continue to provide guidance to the MAs with
hazard mitigation project grant applications and their implementation. Additional fiscal capabilities of the
jurisdictions to implement a hazard mitigation project are detailed in their individual capabilities
assessments.
Final I August 2019 4-7
SECTION FOUR Mitigation Strategv
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Final I August 2019 4-8
SECTION FIVE Plan Maintenance
SECTION 5 PLAN MAINTENANCE
This section of the Plan describes the formal process that will ensure that the Plan remains an active and
relevant document. The Plan maintenance process includes a schedule for monitoring and evaluating the
Plan annually and producing a plan revision every five years. This section describes how the Member
Agencies (MAs) will integrate public participation throughout the plan maintenance process. It also
describes how the MAs intend to implement the Plan and incorporate the mitigation actions identified in
the Plan into existing planning mechanisms and programs. The Plan's format, organized with
Jurisdictional Annexes, allows the MA's to readily update sections when new data becomes available,
ensuring the Plan remains current and relevant.
5.1 MONITORING, EVALUATING AND UPDATING THE PLAN
5.1.1 Plan Maintenance
MWDOC will be responsible for initiating Plan reviews and coordinating with the MAs. The internal
planning teams for each jurisdiction will meet quarterly to review progress on Plan implementation.
MWDOC and the MA's will meet annually, or following a hazard event as described below, to monitor
the Plan's progress and implementation. This will also allow the opportunity for updates to hazards,
jurisdictional goals and mitigation action items, as necessary. If needed, the MAs will coordinate with
MWDOC to integrate updates into the Plan.
5.1.2 Plan Evaluation
The Plan will be evaluated by the MAs at least annually to determine the effectiveness of the Plan, and to
reflect changes in land development or programs that may affect mitigation priorities. MWDOC and the
Planning Team leads (or their jurisdictional representative) will also review the goals and action items to
determine their relevance to changing situations in the County, as well as changes in State or Federal
regulations and policy. MWDOC and MA representatives will also review the risk assessment portion of
the Plan to determine if this information should be updated or modified, given any new available data.
The MAs will report on the status of their projects, the success of various implementation processes,
difficulties encountered, success of coordination efforts, and which strategies should be revised. Any
updates or changes necessary will be forwarded to MWDOC for inclusion in further updates to the Plan.
MWDOC, with input from the Planning Team, will create a template to guide the Planning Team in
preparing a progress report. This will help to ensure consistent and accurate tracking of the Plan
implementation by each of the MAs. Each MA will coordinate with their responsible
departments/agencies identified for each mitigation action. These responsible departments/agencies will
help to monitor and evaluate the progress made on the implementation of mitigation actions and report to
the MA's Planning Team representative on a semi-annual basis. These responsible departments/agencies
will be asked to assess the effectiveness of the mitigation actions and modify the mitigations actions as
appropriate. The HMP Mitigation Action Progress Report worksheet will assist Planning Team
representatives in reporting the status and assessing the effectiveness of the mitigation actions. The
following questions will be considered in evaluating the Plan's effectiveness:
• Has the nature or magnitude of hazards affecting the planning area/jurisdiction changed?
• Are there new hazards that have the potential to impact the planning area/jurisdiction?
• Do the identified goals and actions address current and expected conditions?
Final I August 2019 5-1
SECTION FIVE Plan Maintenance
• Have mitigation actions been implemented or completed?
• Has the implementation of identified mitigation actions resulted in expected outcomes?
• Are current resources adequate to implement the HMP?
• Should additional local resources be committed to address identified hazards?
Future updates to the HMP will account for any new hazard vulnerabilities, unusual circumstances, or
additional information that becomes available. Issues that arise during monitoring and evaluating the
HMP, which require changes to the risk assessment, mitigation strategy and other components of the
Plan, will be incorporated into the next update of the HMP, described below.
5.1.3 Plan Updates
Title 44 Section 201.6( d)(3) of the Code of Federal Regulations requires that local hazard mitigation plans
be reviewed, revised if appropriate, and resubmitted for approval in order to remain eligible for mitigation
project grant funding. Monitoring the progress of the mitigation actions, as described above, will be on-
going throughout the five-year period between the adoption of the HMP and the next update effort. The
five-year cycle may be accelerated to less than five years based on the following triggers:
• A presidential disaster declaration that impacts one or more of the MAs;
• A hazard event that causes loss of life.
Should a significant hazard occur within the planning area, the HMP Planning Team will reconvene
within 60 days of the disaster to review and update the HMP, as required.
MWDOC, working in conjunction with the MAs, will serve as the primary responsible agency for updates
to the Plan. All MAs will be responsible to provide MWDOC with jurisdictional-level updates to the
Plan when/if necessary, as described above. Every five years the updated plan will be submitted to Cal
OES and FEMA for review.
The intent of the update process will be to add new planning process methods, MA profile data, hazard
data and events, vulnerability analyses, mitigation actions, and goals to the adopted Plan so that the HMP
will always be current and up to date. Based on the needs identified by the Planning Team, the update
will, at a minimum, include the elements below:
• The update process will be convened MWDOC and a Planning Team comprised of at least one
representative from each MA.
• The hazard risk assessment will be reviewed and updated using best available information and
technologies on an annual basis.
• The evaluation of critical infrastructure and mapping will be updated and improved as funding
becomes available.
• The mitigation actions will be reviewed and revised to account for any actions completed,
deferred, or changed to account for changes in the risk assessment or new policies identified
under other planning mechanisms, as appropriate.
• The draft update will be made available to appropriate agencies for comment.
Final I August 2019 5-2
SECTION FIVE Plan Maintenance
• The public will be given an opportunity to comment prior to adoption.
• The governing bodies for each MA will adopted the updated HMP.
5.1.4 Adoption
Each jurisdiction is responsible for adopting the HMP. This formal adoption should take place every five
years. Once the Plan had been adopted, MWDOC will be responsible for final submission to Cal OES.
Cal OES will then submit the Plan to FEMA for final review and approval.
5.1.5 Implementation Through Existing Programs
The effectiveness of the nonregulatory HMP depends on the implementation of the Plan and incorporation
of the outlined mitigation action items into existing plans, policies, and programs. The Plan includes a
range of action items that, if implemented, would reduce loss from hazard events in the planning area.
Together, the mitigation action items in the HMP provide the framework for activities that the MAs may
choose to implement over the next five years. The MAs have identified the Plan's goals and prioritized
jurisdiction-specific actions that will be implemented (resources permitting) through existing plans,
policies, and programs.
Implementation of the Plan will be the responsibility of each MA. Successful implementation is more
likely if the Plan recommendations are integrated into other plans and mechanisms, such as water and
wastewater master plans, urban water management plans, general plans, municipal codes, strategic plans
and capital improvement plans and budgets for each of the participating jurisdictions. Upon adoption of
the Plan, the MAs can use the Plan as a baseline of information on the hazards that impact their
jurisdictions. The Plan can also build upon related planning efforts and mitigation programs that are
already occurring within the planning area. This will also facilitate applying for funding opportunities as
they become available. Progress on implementing mitigation actions through other planning programs
and mechanisms should be monitored and integrated into future updates.
By adopting a resolution approving this HMP, each MA agrees to reference and incorporate the document
into their future local planning documents, codes, decisions, processes and regulations. The HMP will be
reviewed and considered by each MA, as applicable plans are created or updated in the future. Upon
creating or updating new plans or policies, each MA will review this HMP and consider the following:
•What hazard and/or vulnerability information should be considered and/or integrated into this
plan?
• Are there opportunities for this plan to support and/or implement mitigation actions?
•What mitigation actions can and should be integrated into this plan?
• Are there other community mechanisms that mitigation can be integrated?
•Is there information from this plan or policy that can be integrated into the next HMP update?
Further, the Water Emergency Response Organization of Orange County's (WEROC) Programs Manager
will establish as an annual agenda item to review and discuss incorporation of the HMP into local
planning efforts and processes.
Final I August 2019 5-3
SECTION FIVE Plan Maintenance
Some of the ways each MA will integrate information from this HMP into their planning mechanisms are
described below.
Planning and zoning law requires all California cities to adopt a comprehensive, long-term general plan
for the physical development of the city. The plans are required to address natural hazards that could
impact a community. Further, recent legislation requires jurisdictions to conduct a vulnerability
assessment that identifies the risks that climate change poses to the local jurisdictions. Through adoption
of their General Plans and Zoning Ordinances, cities plan for the impact of natural hazards. Water and
wastewater agencies also utilize City General Plans to understand natural hazards impacting the areas
they serve and to identify future development and growth and the associated demands for water and
wastewater services. This information informs various water and wastewater plans, such as, Capital
Improvement Programs and Urban Water Management Plans. Each jurisdiction will use these plans and
this HMP as complementary documents that work together to reduce the risk of natural hazards on their
community.
The timing of updates to planning documents vary depending upon the document and statutory
requirements. The information provided in the hazards profiles, vulnerability assessment, and the
mitigation actions will be integrated directly or incorporated by reference to support and enhance
goals/policies and specific actions for each MA. This will be done as the documents are updated by each
jurisdiction. More specifically, upon their next General Plan updates, cities will incorporate updated
hazard and vulnerability information from the HMP, including integration of mitigation actions into their
goals and policies. This is typically done in part through preparation of an Existing Conditions Report or
an update of existing conditions within the various General Plan elements. Through the process of
updating a General Plan, goals, policies and implementation actions are reviewed and new goals, policies,
and actions are created to address issues or concerns within the community, including natural hazards.
Hazard information will identify the exposure of populations, land uses, and critical infrastructure from
hazards. A General Plan update includes a community outreach process that allows direct input from the
community on these issues and provides an opportunity to educate the public on hazards and
opportunities to reduce their impact. A General Plan update also requires recommendation for adoption
and/or adoption by the cities' respective Planning Commissions and City Councils, further ensuring its
implementation as future projects are required to be assessed for their consistency with a General Plan
prior to approval.
Similarly, updated water and wastewater plans will integrate more current hazard and vulnerability
information and establish or update their framework for implementing actions identified in the HMP.
Upon creating or updating any plans, water and wastewater agencies will review this HMP to ensure
integration of the mitigation actions into the respective plans. This will be done as staff assesses the
current plan and incorporates updated hazard information and the mitigation actions from this HMP.
The Urban Water Management and Planning Act was passed in 2010 and requires water suppliers to
estimate water demands and available water supplies. Each water district has an Urban Water
Management Plan (UWMP). UWMPs are required to evaluate the adequacy of water supplies including
projections of 5, 10, and 20 years. These plans are also required to include water shortage contingency
planning for dealing with water shortages, including a catastrophic supply interruption.
Final I August 2019 5-4
SECTION FIVE Plan Maintenance
UWMPs are intended to be integrated with other urban planning requirements and management plans.
Some of these plans include city and county General Plans, Water Master Plans, Recycled Water Master
Plans, Integrated Resource Plans, Integrated Regional Water Management Plans, Groundwater
Management Plans, Emergency Response Plans, and others. Each water district will review the HMP in
coordination with preparation of UWMP updates to ensure the most current hazard information is
provided and that the appropriate mitigation actions are incorporated.
Additionally, all water utilities are required to conduct Risk and Resilience Assessments (RRA) and
corresponding Emergency Response Plans (ERP) in the coming year per the America's Water
Infrastructure Act of 2018 (A WIA). The Risk and Resilience Assessments are similar to the hazard
mitigation risk assessment process in that various risks are assessed, but typically in a more in depth
manner by not just evaluating the risk, but also all potential physical and cyber components of operations
and business continuity. A WIA requires water utilities to assess their facilities for all-hazard risks, but
specifically calls attention to physical security, natural hazard risks, cyber security, fiscal processes
security, and climate change. The corresponding Emergency Response Plan (ERP) is more similar to an
overall FEMA based hazard mitigation plan, than a traditional emergency response plan for say a
jurisdiction with an EOC. The ERP typically addresses possible mitigations or solutions very specific to
identified risks. Both the RRA and the ERP are documents that are considered Protected Critical
Infrastructure Information (PCII) due to information within the documents related to the water
infrastructure. However, MA will integrate pertinent information from this mitigation plan into their
updated RRA and ERPs, as well as utilize those documents to continue to update and enhance the HMP.
Wastewater agencies are also required to maintain current Sewer Master Plans, Sanitary Overflow
Response Plans, and Fats, Oils, and Grease Ordinances. These plans can help to support hazard mitigation
efforts, as well as shape future policy to reduce the impacts of sewer system failures.
Each MA has its own budget process, including CIPs that identify capital projects and equipment
purchases. These systems provide a link between a MAs general and/or strategic plan and annual budget.
As part of the annual review and update of the CIP, the mitigation actions identified in this HMP will be
reviewed to determine which actions should be included within the CIP.
This HMP will be added or incorporated by reference into each MA' s emergency plans (e.g., Emergency
Operations Plans, Emergency Response Plans, and Emergency Evacuation Plans) as they are updated.
The hazard profiles, risk assessment, and mitigation actions will be reviewed during updates to these
plans. Further, mitigation actions not currently provided in the HMP will be identified for consideration
as part of the HMP update.
Other opportunities for integration of this HMP include education programs and continued coordination
between the MAs and other agencies. Each MA maintains a website and utilizes social media to provide
updated information to its community and service area. Hazard information and opportunities for the
community to reduce individual exposure to hazards will be provided. Some MAs will also provide in-
person educational events and activities to further inform the community.
Final I August 2019 5-5
SECTION FIVE Plan Maintenance
5.1.6 Continued Public Involvement
MWDOC is dedicated to involving the public directly in review and updates of the Plan. MWDOC and a
representative from each participating jurisdiction will be responsible for monitoring, evaluating, and
updating the Plan as described above. During all phases of plan maintenance, the public will have the
opportunity to provide feedback.
The most current copy of the Plan will be publicized and permanently available for review on MWDOC's
website at www.mwdoc.com/weroc/Hazard-Mitigation. The site will contain contact information to
which people can direct their comments and concerns. All public feedback will be forwarded to the
appropriate jurisdiction for review and consideration for incorporation (if deemed appropriate) into the
next plan update. This information will also be forwarded to MWDOC, responsible for keeping track of
public comments on the Plan. In addition, copies of the Plan will be catalogued and kept at all the
appropriate agencies in the county. The existence and location of these copies will also be posted on the
MWDOC website. This will provide the public an outlet for which they can express their concerns,
opinions, or ideas about any updates/changes that are proposed to the Plan.
Final I August 2019 5-6
SECTION SIX References
SECTION 6 REFERENCES
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