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SLUDGE DIGESTER REHABILITATION AT PLANT NO. 1 PROJECT P1-100
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Plant No . 1 Digesters
Before P1 -100 & P1 -101 Projects
PRIMARY
CLARIFIER DIGESTER BELT FILTER
PRESSES CAKE CAKE
STORAGE LOADOUT
DISSOLVED AIR
SECONDARY FLOTATION
CLARIFIER THICKENERS
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After P1 -100 & P1 -101 Projects
PRIMARY THICKENING
CLARIFIER CENTRIFUGE DIGESTER
DEWATERNG CAKE CAKE
CENTRIFUGE STORAGE
LOADOUT
71-F17 - i ---00-N,
SECONDARY
CLARIFIER
Plant No . 1 Digesters
Digester Year Built Most Recent
Cleaning Prior
to P 1 -100
5 1959 N/A - Holding - -
6 1962 N/A - Holding
7 1964 N/A — Empty
8 1970 N/A — Empty
,
9 1978 2003 e
10 1978 2003 ram;
11 1993 2007
12 1993 2003
13 1993 2009
14 1993 2004
15 1993 2008
16 1993 2002 :
Project Challenges
• Unknown and unanticipated conditions
— Higher volume and concentration of sludge
— Extensive PVC T-lock repairs at all digesters
— Additional mechanical repairs and replacements
— Concrete repairs inside digesters
• Extra work resulted in delays with cost
impacts
— Delay mitigation or recovery was minimal due to
sequenced schedule.
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12/ 11 /2014 10 ' 11
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Digesters Cleaning ( Before After)
MORON =20
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Concrete Dome
Repairs
1,7
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Concrete Dome Repairs
for-
_ Exposed rebar showing
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possible severe corrosion
A pocket of concrete where the
rebar is exposed and corrosion is
evident (moderate to severe). '
Exposed Rebar at Digesters
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PVC TmIock Repairs Inside Digesters
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Unanticipated condition -
encountered at all
digesters.
PVC Tmlock Repairs Inside Digesters
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ExistingPiping Conditions
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Cone leak, Digester 16
Hole in mix pump
suction Line Digester 9
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Possible Future Unknown Conditions
• Replacement valves in lieu of rehabilitation
• Leak repair at existing pipes inside digesters
• PVC T-lock repairs & scaffolding
• Concrete crack and corrosion repairs
• Manway corrosion repairs
• Cleaning interior of existing piping
Lessons Learned
• Rehabilitate in smaller groups (i .e. limit risk exposure)
• Additional condition assessment during design
• Consider end of life replacement vs rehabilitation
• Clean on separate contracts if possible. If not possible,
specify sludge removal carefully.
• Replace equipment completely vs. rehabilitate or
partial replacement.
4 , .
Recommended Action
• Approve a budget increase of $500,000 for Sludge Digester
Rehabilitation at Plant No. 1, Project No. P1-100, for a total
budget amount of $67,150,000; and
• Approve a contingency increase of $837,500 (2.5%) to the
construction contract with JR Filanc Construction Company
for Sludge Digester Rehabilitation at Plant No. 1, Project No.
P1-100, for a total contingency of $9,212,500 (27.5%).