Start
1.
Review strategic
levels of service &
tolerable risk limits
2.
Review minimum
levels of
performance at
asset level
4.
Review condition,
performance
3.
Review business
rules for service
level & capacity
failure
Conceptual Decision Process Flow:
“End of Asset Life” and its role in the
Asset Reinvestment Decision
(This process is executed on a periodic, recurrent basis)
No
6.
Review likelihood
of failure score
5.
Is performance
score/capacity
≥ designated
trigger?
The Asset
Reinvestment
Logic Diagram
Yes
8.
Review
consequence of
failure score
7.
Review remaining
effective life
9.
Review current
risk mitigation
strategies
10.
Review Business
Risk Exposure
score (BRE)
11.
Is BRE within
tolerable risk
limits?
No
12.
Determine feasible
risk mitigation
alternatives
Yes
16.
Continue to run
and monitor
(to step 3)
13.
Project life cycle
costs of feasible
alternatives
No
15.
Is proactive
reinvestment
cost effective?
14.
Test proactive
strategy?
Yes
(Yellow Flag
Rule)
Yes
Legend
No
Associated template
17.
Within CIP/Ops
budget
window?
Link to PowerPoint slides
Decision node
Associated workbook or
worksheet
No
(Red Flag
Rule)
Yes
Link to advanced materials
Flow termination
18.
Schedule for
funding
Action step
End
End of Asset Life Reinvestment
Decision Support Tool
1
Alignment of O&M and capital activities with
organizational Level of Service strategies
Organizational strategies
LOS performance targets:
strategic (customer) and
tactical (asset unit) levels
Agency-wide asset
performance targets
End of Asset Life Reinvestment
Decision Support Tool
LOS drives work
planning through workRoutine O&M
order priority code
activity
Plan
Control
Eval.
and capital
cycle
Schedule
Execute
2
System performance requirements
Assets
Processes Facilities
Systems
Manage
here…
Network Collection Systems
Trunk Sewer Systems
Treatment Plant
Disposal System
Unique LOS for each
asset
…to get
performance here
External LOS Targets
NPDES permit
● 10 mg/L, BOD
● 15 mg/L, SS
● 2 mg/L, TN
● 1 mg/L, P
Final Discharge
and Disposal
LOS - level of service, NPDES - National Pollutant Discharge Elimination System, BOD biochemical oxygen demand, SS - suspended solids, TN - total nitrogen, P - phosphorus
End of Asset Life Reinvestment
Decision Support Tool
3
2 Examples: Operational level asset performance
standards (minimum performance standards)
NO.
1
2
ITEM
FUNCTION
OPERATING
MAXIMUM TIMES FOR LOSS OF
RANGE
SERVICE
AT 100%
LOSS
AT 50% LOSS
CONSEQUENCE/COMMENT
1
Basin COD
feed pumps
To provide COD feed (partially treated
settled raw sewage from the anaerobic
basin) to the activated sludge basin at
an average rate of 15 Mgal/d (0.3Q)
5-20 Mgal/d
24 hr
48 hr*
COD supply is essential for N removal, without the
supply, N-removal will fail. In addition load on
aerated lagoon will increase by 0.3Q, increasing
the risk of odor generation. * Relates to average
flow.
2
Activated
Sludge Basin
inlet pumps
To feed activated sludge basin at an
average rate of 35 Mgal/d with pond 4
effluent
25-67
Mgal/d
24 hr
48 hr*
Will result in no N-reduction. No feed to ASB will
result in bypass via overflow from P#4 to P#5. The
volume bypassed will depend on level in lagoon 4
before failure. * Relates to average flow.
3
Return
Activated
Sludge
pumps
To remove sludge at a concentration of
around 1% from the secondary clarifiers
at an average total flow of 50 Mgal/d
25-75
Mgal/d
1 hr
12 hr
Build up of sludge, leading to sludge carry over in
P#5 and reduction in N removal. Longer could be
tolerated if ASB feed is stopped or mixing and
aeration turned off.
Engineers determine that a clarifier requires a hydraulic pump to sustain 3000 psi +/- 200 psi on a
continuous basis to achieve the process design – the clarifier’s function. This level then becomes the
asset performance standard.
“Provide sustained hydraulic pressure of 3000 psi +/- 200 psi for 24 hours a day 7 days a week.”
End of Asset Life Reinvestment
Decision Support Tool
4
Relating capacity to asset performance levels
Current
Demand
Stream
SupplyProduction
Stream
Future
Demand
Stream
Assets
Available
Capacity Gap
Assets
Required
“Excess
capacity?”
When?
How big?
Performance level (minimal) requirement statements become
triggers to determine when to reinvest!
End of Asset Life Reinvestment
Decision Support Tool
5