HomeMy Public PortalAboutExhibit MSD 11A11 SKME Priority Ranking 1
Sverdrup|Kwame|Metcalf & Eddy Joint Venture (S|K|M&E JV)
5257 Shaw Avenue, Suite 302 Telephone: (314) 773-4990
St. Louis, Missouri 63110 Fax: (314) 773-4790
Memorandum – Project Ranking Criteria
Rev. 3, August 29, 2002
In accordance with Task 2.2.5 and Table 3.1 of our Agreement, this memorandum
presents recommendations on a system for ranking the various projects that comprise
MSD’s capital improvement and replacement program database. The memorandum
covers the overall philosophy used to establish the system and the proposed ranking
criteria and evaluation tools.
Ranking Philosophy
The ranking of projects is a key component in the development of the MSD’s Capital
Improvement and Replacement Program (CIRP). The ranking and prioritization process
must assure that the high-level goals and strategic issues that define the program are
applied to develop an optimum CIRP.
MSD currently has a number of ranking processes:
Category “A” Sanitary Relief Projects Priority Rating (< $1.5 million)
Category “B” Sanitary Relief Projects Priority Rating (> $1.5 million)
Category “C” Infrastructure Projects Priority Rating (City projects)
Stormwater Priority Ranking System (not currently in use)
Stormwater System Master Improvement Plan Benefit Points
Priority Points System for City of St. Louis Sewers (currently being verified by
MSD)
Treatment Plant and Pump Station Project Rankings
These existing ranking systems generally provide consistent evaluations of projects
within single project categories, and provide the basis for prioritizing projects within
those individual categories.
For the CIRP planning effort, the projects comprising the program have been divided
into two categories – stormwater and infrastructure. Each of these categories will be
funded separately and hence a separate ranking system is appropriate for each.
For stormwater projects, the current Stormwater System Master Improvement
Plan Benefit Points system will be used, as is, to prioritize the projects.
For infrastructure projects, it will be necessary to expand upon the scope of the
current ranking systems so that a single process can be applied to projects with
diverse goals and benefits. For example, a project that eliminates basement
backups needs to be compared with a control system upgrade at a treatment
plant, in order to properly sequence these projects within the overall program.
Accomplishing this requires that the various factors used to evaluate projects
Memorandum – Project Ranking Criteria Rev. 3, August 29, 2002
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with differing goals and benefits be distilled to a single criterion. A benefit-to-cost
ratio has been selected as that criterion. The determination of each project’s
benefit is the heart of the process, and it is here that careful consideration of the
program’s long-term goals and critical issues is paramount.
The following pages describe the recommended approach to ranking projects. This
approach incorporates MSD’s existing prioritization systems and adds several new
components, thereby providing a method for comparison of projects within differing
categories.
Recommended Ranking Process
For purposes of this planning effort, a “project” is defined as the consolidation of various
“sub-projects” that work together to solve a problem. The subdividing of projects, for
example, into construction packages or phases, will be reflected in the total project’s
schedule. For ranking purposes, the project will be ranked once, as a total project; each
individual phase will not be ranked.
Figure 1 on page 4 depicts the project ranking process to be used. Each project will
initially be subjected to two questions:
Is the project currently mandated (e.g., by a settlement agreement)?
Is the project currently under construction?
If the answer to either question is yes, a detailed benefit-cost analysis is not necessary
for that project, because the project’s priority within the overall program has already
been established.
Each project is then evaluated using two “pass-fail” questions:
Is the project consistent with MSD’s long-term goals? For example, is the
project the ultimate solution to a problem? Is it a proper component of a well-
conceived plan to resolve a problem? The goal of asking these questions is to
eliminate or cause to be redefined any project that provides only a quick and
obsolescent fix, unless it is a necessary part of a proper long-term plan.
Is the project consistent with regulatory trends, including such items as
existing and future permit requirements and evolving SSO, CSO, TMDL,
flow blending, and storm water regulations? For example, does a proposed
peak excess flow treatment system comply with NPDES permitting trends, or will
a proposed CSO project still be valid after Missouri completes its current round of
water quality standard revisions?
Failing either or both of these tests relegates the project to a low/no-priority basis, to the
Operations Infrastructure Repair budget, or requires the project to be redefined such
that it can pass these tests.
Most projects will proceed through these initial four questions to the actual ranking
process. The first step is to determine the benefit points for the project, as described
Memorandum – Project Ranking Criteria Rev. 3, August 29, 2002
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below. Cost data is then fed into the process, and a benefit-to-cost ratio calculated. This
parameter is then used to prioritize the projects, from a high to low ratio.
Finally, two other factors are taken into consideration.
The first is whether there are implementation issues that might affect the project.
These would include items such as difficulty in obtaining easements and permits,
or construction through congested areas. While these types of issues have no
bearing on the long-term benefit of a project, they could affect the time frame in
which a project could actually be implemented. The impact of these issues will be
determined, and adjustments made in the project’s implementation schedule to
account for them. For example, a longer-than-normal lag time between design
and construction may be required for easement acquisition, if this has been
identified as an implementation issue for a particular project.
The final factor to be considered is whether the project is adjacent to another
project (e.g., stormwater and infrastructure project in close proximity). In such
cases, it may be desirable to “package” the projects together and re-evaluate
them, based on cost and schedule, to determine if packaging the projects would
impact the prioritization of the individual projects.
Benefit Points Methodology – Stormwater Projects
For projects that control stormwater flooding and/or erosion, MSD’s Stormwater System
Master Improvement Plan (SSMIP) Benefit Points System will be used to determine the
benefits derived from implementing the projects1. This system assigns benefit points
based on four basic criteria:
Number of structures or properties impacted – points are accumulated in the
system for each property/structure/roadway affected by stormwater flooding or
erosion.
Flooding frequency – the system assigns points based on the frequency of
flooding by examining both a 15-year flood and a 100-year flood. A higher
number of points are calculated for properties/structures/roadways that are
impacted more frequently.
Flooding type and severity – points are assigned based on the type and severity
of flooding, e.g., basement vs. first floor vs. yard flooding for homes, arterial vs.
collector vs. residential vs. emergency access for streets.
Erosion risk type and severity - points are assigned based on the type and
severity of erosion, e.g., habitable structures vs. industrial buildings, and distance
from structures to erosion boundary.
Figure 2 provides the details on how points are assigned for each property, structure, or
street in the SSMIP Benefit Points System.
1 Note that stormwater projects that resolve water quality problems (e.g., Phase II Stormwater projects)
are evaluated as infrastructure projects.
Memorandum – Project Ranking Criteria Rev. 3, August 29, 2002 4 DETERMINEBENEFITPOINTSPRIORITIZE PROJECTSIS PROJECT CONSISTENT WITH MSD’S LONG-TERM GOALS?IS PROJECT CONSISTENT WITH REGULATORY TRENDS?IS PROJECT UNDER CONSTRUCTION?DETERMINEBENEFIT/COSTRATIOANY IMPLEMENTATION ISSUES?PROXIMITY OR LINKAGE TO STORMWATER PROJECTS?DETERMINE IMPACT ON PROJECT SCHEDULEREPACKAGE AND RE-EVALUATE IN TERMS OF COST AND SCHEDULEIS PROJECT CURRENTLY MANDATED?COST DATAYESYESNONONONONOYESYESNOYESYESSTOP -PRIORITY ALREADY SETNONOREDEFINE OR DROPFIGURE 1PROJECT RANKING PROCESS OVERVIEW
Memorandum – Project Ranking Criteria Rev. 3, August 29, 2002
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FIGURE 2
Metropolitan St. Louis Sewer District
Stormwater System Master Improvement Plan
Benefit Points
Points Units
Frequent Structural Flooding (15 Year Flood)
Habitable first floor 300 Unit
Basements 200 Unit
Miscellaneous structures including patios/decks, pools, sheds, tennis courts, etc. 50 Unit
Yard flooding 10 Lot
Industrial building 300 2500 sf
Frequent Roadway Flooding (15 Year Flood)
Emergency access restricted to any habitable structure 200 Lot
Traffic obstruction on arterial streets 50 250 ft
Traffic obstruction on collector streets 25 250 ft
Traffic obstruction on residential streets 10 250 ft
Infrequent Structural Flooding (100 Year Flood)
Habitable first floor 45 Unit
Basements 30 Unit
Miscellaneous structures including patios/decks, pools, sheds, tennis courts, etc. 7 Unit
Yard flooding 2 Lot
Industrial building 45 2500 sf
Infrequent Roadway Flooding (100 Year Flood)
Emergency access restricted to any habitable structure 30 Lot
Traffic obstruction on arterial streets 7 250 ft
Traffic obstruction on collector streets 4 250 ft
Traffic obstruction on residential streets 2 250 ft
High Risk Structural Erosion (within 25 feet of structure)
Habitable structures 200 Unit
Miscellaneous structures including patios/decks, pools, sheds, tennis courts, etc. 100 Unit
Industrial buildings 200 2500 sf
High Risk Roadway Erosion (within 25 feet of structure)
Arterial 100 250 ft
Collector 50 250 ft
Residential 25 250 ft
Low Risk Structural Erosion (greater than 100 feet from structure)
Yard Erosion 10 Lot
Moderate Risk Structural Erosion (within 26 to 100 feet of structure)
Habitable structures 50 Unit
Miscellaneous structures including patios/decks, pools, sheds, tennis courts, etc. 25 Unit
Industrial buildings 50 2500 sf
Moderate Risk Roadway Erosion (within 26 to 100 feet of structure)
Arterial 25 250 ft
Collector 13 250 ft
Residential 6 250 ft
Memorandum – Project Ranking Criteria Rev. 3, August 29, 2002
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Benefit Points Methodology – Infrastructure Projects
Table 1 on the following page depicts the criteria to be used in establishing the benefit
points for each infrastructure project. Six basic Project Types have been defined, as
listed below, depending on the ultimate goal for the project. Each project is placed into a
single Project Type category, with the exception of projects that are intended to control
SSOs or CSOs and also reduce basement backups. These projects will be placed into
both Project Types, and have benefit points calculated for each and combined.
Control Sanitary Sewer Overflows – This category includes projects whose main
purpose is improve water quality by conveying, storing, or removing additional
flow, thereby resulting in the reduction or elimination of overflows to receiving
streams. These projects are largely regulatory-driven. Typically, this category
would include sanitary relief projects that result in the elimination of existing
sanitary bypasses. This category would also include capacity upgrades to
sanitary pump stations and treatment plants. If the project also results in the
elimination of basement backups, then the project would also receive benefit
points under “Eliminate Basement Backups.”
Control Combined Sewer Overflows – This category includes regulatory-driven
projects intended to improve water quality by reducing the frequency or
magnitude of combined sewer overflows and/or pollutant loadings associated
with permitted overflows. If the project also results in the elimination of basement
backups, then the project would also receive benefit points under “Eliminate
Basement Backups.”
Eliminate Basement Backups – This category represents projects that are
designed to eliminate backups of sewage into the basements of homes or other
buildings that result from wet weather or other conditions. These projects are
largely customer-driven.
Rehabilitate Infrastructure – The primary purpose of projects in this category is to
increase the life expectancy of existing infrastructure by repairing or replacing
aged or degraded facilities. If a project in this category also results in fewer
overflows, due to increased capacity or less infiltration or inflow, then it would be
assigned benefit points in other categories as well.
Meet Discharge / Permit Requirements – This category represents regulatory-
driven stormwater and treatment plant projects; collection system regulatory
projects are covered under the SSO and CSO categories above. The category
includes water, air, and biosolids regulations, and both current and anticipated
future regulations.
Enhance Operational Efficiency – Projects in this category are intended to
increase the efficiency of District operations. Included are such items as capital
equipment replacement, non-mandated treatment plant improvements, and new
buildings/facilities.
Memorandum – Project Ranking Criteria Rev. 3, August 29, 2002 7 Table 1Project Types and Project Ranking CriteriaProject Category Project Ranking Criteria "Pass Fail" Criteria Project Type (Goal) Public Health Public Safety Regulatory Requirements Infrastructure Needs Operational Efficiency Basement Flooding Severity Basement Flooding Frequency Number of Homes/Properties Impacted Number of SSOs Eliminated SSO Activation Frequency Water Quality Improvement (Ben. Uses) Number of CSOs Eliminated CSO Volume or Pollutant Reduction Flooding / Erosion Frequency Flooding / Erosion Severity Type of Structures / Roadways Impacted by Flooding Type of Structures / Roadways Impacted by Erosion Age of Sewer Geotechnical Conditions Pipe Materials Pipe Size Pipe Condition Impact of Failure Historical Problems Comply with Permit Conditions Solves O&M Problem Reduces O&M Costs Provides Additional Flexibility / Capacity Project Cost Benefit / Cost Ratio (Σ Benefit Points/Cost) Consistent with Approved Long-Term Plans/Goals Consistent with Regulatory Trend Project Mandated Already Under Design / Construction Showstoppers (permit, ROW, Easements, Constructability, Implementability) Proximity / link to Other Projects Eliminate Basement Backups X X X B B B o o o o o C B/C√√√√ √ √ Control SSOs X X X X B B B o o o o o C B/C√√√√ √ √ Control CSOs X X X X B B B o o o C B/C√√√√ √ √ Control Flooding / Erosion X X B B B B B o C B/C√√√√ √ √ Rehabilitate Infrastructure X X B B B B B B B B C B/C√√√√ √ √ Meet Discharge / Permit Requirements X X B o B C B/C√√√√ √ √ Enhance Operational Efficiency X X X X B B o o o o B B B C B/C√√√√ √ √Cross-Reference to Current MSD CriteriaA/B A/BA/BSA/B -- A/B -- -- S S S S I I I I I I I -- -- -- -- All --Notes:C = project cost.B/C = Σ Benefit Points / Cost.√ = Pass-fail criteria applicable to all projects.o = Other criteria that relate to the Project Type and/or the primary criteria for determining benefit points.Cross Reference to Current MSD CriteriaA/B = Sanitary Relief Projects Priority RatingS = SSMIP Benefit PointsI = Infrastructure Projects Priority RatingB = Primary criteria for determining project benefit. Ranking will be structured to give a 0 to 100 scale total within each type of project goal. A weighting factor will then be applied, for example, to give "Eliminate Basement Backups" more weight than, for example, "Enhance Operational Efficiency."
Memorandum – Project Ranking Criteria Rev. 3, August 29, 2002
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Each of the six Project Types has been cross-referenced to one or more of the Project
Categories or drivers identified in the Strategic Master Plan:
Public Health – protection of the public from exposure to sewage.
Public Safety – protection of the public from safety hazards associated with
wastewater and stormwater collection, conveyance, treatment, and disposal.
Regulatory Requirements – protection of the environment in accordance with
public laws and regulations.
Infrastructure Needs – rehabilitation of the systems necessary to collect, convey,
treat and dispose of wastewater and stormwater.
Operational Efficiency – improvement in the delivery of services while minimizing
customer costs.
For each of the six Project Types identified above, a system has been developed to
calculate project benefit points on a 0 to 100 scale. These systems are defined in detail
below.
In reality, however, differing project types with the same total of benefit points may not
have equal priority. For example, a project to eliminate basement backups that has
80 benefit points may be a far more important project than one that upgrades a piece of
treatment plant equipment, but has also scored 80 points within its benefit points
system. To account for this, superimposed on these raw ratings will be a weighting
factor for each Project Type, compatible with the overall program goals. The weighting
factors are presented below in Table 2.
Table 2
Project Type Weighting Factors
Project Type Weighting Factor
Eliminate Basement Backups 1.00
Control Sanitary Sewer Overflows 0.90
Control Combined Sewer Overflows 0.75
Rehabilitate Infrastructure 0.50
Meet Discharge / Permit Requirements 1.00
Enhance Operational Efficiency 0.30
Determination of Benefit Points
For each of the six Project Types, the paragraphs below identify the method to be used
to determine the benefit points.
Memorandum – Project Ranking Criteria Rev. 3, August 29, 2002
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Control Sanitary Sewer Overflows
The benefit points system for projects that eliminate or control SSOs is based on the
following criteria:
Stream Classification – Do the overflows discharge to sensitive areas (defined as
Outstanding National Resource Waters, National Marine Sanctuaries, waters with
threatened or endangered species and their habitat, waters with primary contact
recreation, public water intakes or their designated protection areas, shellfish beds)? Is
the receiving stream considered a Metropolitan No-Discharge Stream? Is it on the
State’s 303(d) impaired waters list? What are the receiving stream’s designated uses
(e.g., recreational waters, drinking water supply, wildlife watering, irrigation)?
Frequency of SSO Activation – How frequently are the receiving waters impacted by
SSOs? This may be determined by hydraulic modeling, discharge monitoring, or direct
observation.
Level of Control Provided by Proposed Project – Based on hydraulic modeling, does the
project eliminate overflows to receiving streams or reduce the activation frequency of
SSOs?
The Benefit Points for SSO Control = A x B x C where:
A = Stream Classification Points
(choose the single most stringent category applicable to the receiving stream)
Sensitive Areas (or areas within 2 miles upstream of waters classified for
whole body contact)
10
On Endangered Waters 303(d) List (due to point source discharges) 9
Metropolitan No Discharge Stream 8
Classified Waters – Drinking Water Supply 7
Classified Waters – Secondary Contact Recreation 7
Classified Waters – Aquatic Life Protection / Livestock & Wildlife Watering 6
Classified Waters – Industrial / Irrigation 5
Unclassified 4
B = Frequency of Activation Points
SSOs currently activate in a 2-year storm or greater 10
SSOs currently activate only in a 5-year storm or greater 7
SSOs currently activate only in a 10-year storm or greater 4
C = Level of Control Multiplier (choose highest applicable category)
Project will eliminate SSOs in a 10-year storm 1.0
Project will not eliminate SSOs in a 10-year storm but will reduce volume of
discharge by 50% or more
0.7
Project will not eliminate SSOs in a 10-year storm but will reduce volume of
discharge by less than 50%
0.4
Memorandum – Project Ranking Criteria Rev. 3, August 29, 2002
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Control Combined Sewer Overflows
The benefits of controlling combined sewer overflows can be determined based on the
following criteria:
Stream Classification – Do the overflows discharge to sensitive areas (defined as
Outstanding National Resource Waters, National Marine Sanctuaries, waters with
threatened or endangered species and their habitat, waters with primary contact
recreation, public water intakes or their designated protection areas, shellfish beds)? Is
the receiving stream considered a Metropolitan No-Discharge Stream? Is it on the
State’s 303(d) list? What are the receiving stream’s designated uses (e.g., recreational
waters, drinking water supply, wildlife watering, irrigation)?
Water Quality Impact of CSOs – to what extent are receiving streams degraded by
overflows from the project area? Is the attainment of the receiving stream’s designated
uses impaired by overflows?
Level of Control Provided by Proposed Project – To what extent does the project result
in the elimination of overflows to receiving streams within the project boundaries? If the
project does not eliminate overflows entirely, to what extent does the project reduce the
activation frequency, total volume and/or pollutant loadings from CSOs within the project
boundaries? Does the project result in water quality improvements consistent with the
water quality goals set forth in the District’s Long Term Control Plan (LTCP)?
For determining the benefit of CSO projects, a point system similar to that used for
Sanitary Sewer Overflows is to be used:
The Benefit Points for CSO Control = A x B x C where:
A = Stream Classification Points
(choose the single most stringent category applicable to the receiving stream)
Sensitive Areas (or areas within 2 miles upstream of waters classified for
whole body contact)
10
On Endangered Waters 303(d) List (due to point source discharges) 9
Metropolitan No Discharge Stream 8
Classified Waters – Drinking Water Supply 7
Classified Waters – Secondary Contact Recreation 7
Classified Waters – Aquatic Life Protection / Livestock & Wildlife Watering 6
Classified Waters – Industrial / Irrigation 5
Unclassified 4
B = Water Quality Impact Points (choose highest applicable category, based
on water quality impact findings of Long Term Control Plan)
CSOs impair the attainment of designated uses in receiving stream (i.e.,
demonstrated chronic water quality issues)
10
CSOs result in short term exceedences of water quality standards 8
CSOs result in visible (aesthetic) pollution 7
No demonstrable effect of CSOs on water quality 3
Memorandum – Project Ranking Criteria Rev. 3, August 29, 2002
11
C = Level of Control Multiplier (choose highest applicable category)
Total elimination of overflows or associated pollutant loadings to the
receiving stream
1.0
80% reduction in CSO number, volume, activation frequency -or-
reduction in pollutant loading(s) consistent with LTCP
0.9
60% reduction in CSO number, volume, activation frequency -or-
reduction in pollutant loading(s) consistent with LTCP
0.8
40% reduction in CSO number, volume, activation frequency -or-
reduction in pollutant loading(s) consistent with LTCP
0.6
20% reduction in CSO number, volume, activation frequency -or-
reduction in pollutant loading(s) consistent with LTCP
0.3
Eliminate Basement Backups
The benefit points system for projects that eliminate basement backups is based on
three criteria:
Basement flooding severity – is the flooding characterized by ponding around the
floor drain only, whole basement ponding up to 6 inches deep, or ponding over
6 inches deep?
Basement flooding frequency – is the flooding chronic, has it occurred in a
problem area in six or more separate years?
Number of homes impacted – includes known complaints as well as houses/lots
between known complaints.
MSD’s Category “A” and Category “B” Sanitary Relief Projects Priority Rating Systems
provide a long-established and well-tested method for calculating these benefit points
(see Figure 3). The “severity” factor in the rating system (component A) addresses not
only the actual severity of basement flooding, but also addresses flooding frequency
through the assignment of additional points for chronic problems. Component B of the
rating system assigns points based on the number of homes affected2. The benefit
points calculated from components A and B of the existing rating systems will be
multiplied by 1.43 (for Category “A” projects) or 1.82 (for Category “B” projects) to obtain
a point value on a scale of zero to one hundred3.
2 For conceptual Category B projects, component B may be estimated as 10•log(X/10) where X is the
estimated number of tributary homes calculated by dividing the average daily dry weather flow at the
downstream end of the project (from the sub-watershed model) in gallons per day by 280 gallons per
day per home.
3 A total of 70 points are possible for Category A projects for components (A) and (B). Similarly, a total of
55 points are possible for Category B projects for components (A) and (B). The multipliers of 1.43 and
1.82 are used to adjust these totals to 100.
Memorandum – Project Ranking Criteria Rev. 3, August 29, 2002
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These criteria
form the
basis for
determining
the benefit of
eliminating
basement
backups
FIGURE 3.BASEMENT BACKUP BENEFIT POINTS
Memorandum – Project Ranking Criteria Rev. 3, August 29, 2002
13
Rehabilitate Infrastructure
For projects that replace or rehabilitate deficient infrastructure, the project benefit can
be based on the probability and consequence of a failure. The following factors have
been identified as relevant to making this assessment:
Age of sewer, taking into consideration subsequent rehabilitation efforts
Geotechnical conditions, including bedding type, depth of cover, groundwater
elevation relative to pipe
Pipe material, such as clay, plastic, masonry, concrete
Pipe size
Pipe condition, including evidence of cracks, deflection, corrosion, missing or
worn masonry, deteriorated or open joints, or excessive I/I
Impact of failure on surface roads/buildings/lots
Presence of historical problems / frequent repairs
MSD’s Category “C” Infrastructure Projects Priority Rating system provides a method for
determining benefit points on a 0 to 110 scale (see Figure 4).4 To normalize this to a
1 to 100 scale, the priority points should be multiplied by 0.91.
Meet Discharge / Permit Requirements
The selected system for determining the benefit of projects that are implemented to
meet regulatory requirements is as follows:
Projects that eliminate repeated violations 100 points
Projects that eliminate occasional violations 75 points
Projects that eliminate anticipated (future) repeated violations 50 points
Projects that eliminate anticipated (future) occasional violations 25 points
4 MSD’s Priority Points System for City of St. Louis Sewers is an alternate system that could be used to
determine benefit points for infrastructure repair projects. This system is currently in the process of
being calibrated and verified. Until this process is complete and it is determined that this new system
provides reliable and consistent results, it is recommended that the old Category “C” Infrastructure
Projects Priority Rating system be used.
Memorandum – Project Ranking Criteria Rev. 3, August 29, 2002
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FIGURE 4.
BENEFITS POINTS FOR INFRASTRUCTURE REPAIR PROJECTS
CATEGORY “C” INFRASTRUCTURE PROJECTS PRIORITY RATING
|*******************************************************************************************************************************************************|
|PROJECT NAME: | SIZE OF SEWER (Determine the max. | AGE OF SEWER |
| -------------------------------- | ------------- dim. Of sewer regard-| ------------ |
| | less of geometry) | (Assign age points relative to the following criteria |
|PROJECT NUMBER: | CATEGORY POINTS | CATEGORY POINTS |
| | 8” up to 3 feet 1 | Constructed after 1956 1 |
|CALCS BY: DATE: | 3 feet up to 6 feet 2 | Constructed between 1920 and 1956 2 |
| -------------------- ---------- | 6 feet up to 12 feet 3 | Constructed between 1885 and 1920 3 |
| | 12 feet or greater 4 | Constructed prior to 1885 4 |
|*******************************************************************************************************************************************************|
| | SIZE OF TRIBUTARY AREA | GEOTECHNICAL |
| COMPONENT POINTS MULT. WEIGHTED | ---------------------- | ------------ |
| FACTOR FACTOR FACTOR |(Select the best description of tributary | (Numerical value which corresponds to best description of |
| | area, assign points as follows) | geotechnical conditions, see handout on procedures if more |
| AGE OF SEWER 1.625 | | detailed description of geotechnical conditions is required)|
| ---- ----- | AREA LENGTH POINTS | CATEGORY POINTS |
| GEOTECHNICAL 2.750 |Local only < 100 feet 1 | Unknown 1 |
| ---- ----- | | |
| MATERIALS 2.000 |City Blocks Hundreds of Feet 2 | Along former creek bed, ravine, drain 2 |
| ---- ----- | | |
| SIZE OF SEWER 1.625 |Acres Thousands of Feet 3 | In current or former floodplain, high 3 |
| ---- ----- | | groundwater, or seepage noted in sewer |
| INSPECTION 8.000 |Sq. Miles Miles 4 | |
| ---- ----- | | In fill or unsuitable material; or over 4 |
| TRIBUTARY AREA 2.000 | | sinkhole or former pond |
| ---- ----- |--------------------------------------------------------------------------------------------------------|
| IMPACTS 4.000 | IMPACT |
| ---- ----- | ------ CATEGORY POINTS |
| Subtotal |Local only traffic/outage impacts 1 |
|HISTORICAL FACTOR ----- | |
|(Yes = Add 10% to total) |Detourable traffic/flows diver- 2 a) Arterial traffic |
|(see note) ----- |table/only local utility interface b) Heavy sewage flow |
| Total | c) Major utility interference |
| ----- |One of the following (a-d) applies 3 or outage potential |
|Note: Determination of the historical factor | d) Proximate building, bridge or |
| shall be coordinated with Frank Janson |Two of the following (a-d) applies 4 other structure |
| of the Infrastructure Department and | |
| with the Maintenance personnel. |Three of the following (a-d) applies 5 |
|-------------------------------------------------------------------------------------------------------------------------------------------------------|
|MATERIAL | INSPECTION |
|-------- | ---------- |
| | CATEGORY POINTS CATEGORY POINTS |
| |Looks Sound 0 Large hole, earth showing, 5 |
| CATEGORY POINTS | OR major voids around sewer |
|Tunnel in rock, concrete lined 1 |Needs mortar/pointing (worn brick) 1 |
|Tunnel in rock, unlined 2 | Cracks in crown (at least 25% 4 |
| |Bricks missing or exposed rebars, 2 of inspected length |
|Concrete, combination sewer 1 |at least 1 s.f. per 50 s.f. of |
|Concrete, sanitary sewer 3 |surface area within the sewer; ADD Cracks in crown and sides (at 5 |
| |two pts for every additional 1 s.f. least 25% of inspected length |
|Stone walls, brick arch 3 |section per each 50 s.f. section |
|Timber bottom, masonry sides/arch 4 | Obvious vertical or lateral 4 |
|Brick masonry 3 |Offset/open joints or missing segments deflection |
|Total stone masonry 2 |10-25% 3 |
| |25-50% 4 Chemical corrosion, etching 2 |
|Clay pipe or plastic pipe 1 |Greater than 50% 5 Chemical corrosion, exposed rebars 3 |
|-------------------------------------------------------------------------------------------------------------------------------------------------------|
Memorandum – Project Ranking Criteria Rev. 3, August 29, 2002
15
Enhance Operational Efficiency
Projects that enhance operational efficiency fall into one of two categories:
Projects whose benefit that can be readily evaluated in terms of a payback
period, calculated by dividing the project’s capital cost by the annual O&M
savings. An example would be upgrading the belt filter presses at Bissell Point to
reduce sludge disposal costs. In this case, a payback period can be determined
by dividing the capital cost by the annual O&M savings. For projects in this
category, the proposed benefits points are as follows:
For projects with a payback period ≤ 1 year 100 points
For projects with a payback period > 1 and ≤ 2 years 80 points
For projects with a payback period > 2 and ≤ 3 years 60 points
For projects with a payback period > 3 and ≤ 4 years 40 points
For projects with a payback period > 4 and ≤ 5 years 20 points
For projects with a payback period > 5 years 0 points
Other projects that enhance operational efficiency provide benefits that may not
be easily quantified in dollars, e.g., renovating the Mintert Maintenance Facility.
For projects in this category, the proposed benefits points are based on the
frequency of the problem (e.g., from maintenance records) and resulting impact:
Resolves chronic problem with high impact/cost 100 points
Resolves chronic problem with low impact/cost 80 points
Resolves intermittent problem with high impact/cost 60 points
Resolves intermittent problem with low impact/cost 40 points
Resolves infrequent problem with high impact/cost 20 points
Resolves infrequent problem with low impact/cost 0 points
Proposed projects whose primary purpose is to enhance operational efficiency will have
benefit points assigned by one of the two methods outlined above.
Benefit to Cost Ratio Calculation
In testing the above-described project ranking system, it was determined that a simple
benefit to cost ratio gave overwhelming preference to low-cost projects, regardless of
project benefit, while high-cost projects received low priorities, regardless of benefit.
This is demonstrated in the upper half of Figure 5 showing a scatter plot of project
priority vs. cost for a selected sample of projects. The reason for this is that the range of
project benefit points is relatively small (one order of magnitude) whereas project costs
can vary over several orders of magnitude. Therefore, it was decided to use the log of
the project cost in the benefit to cost ratio calculation. As shown on the scatter plot in
the lower half of Figure 5, the use of a benefit to log-cost ratio, for the same sample of
projects, has successfully eliminated the cost bias that existed in the benefit to cost
ratio.
Memorandum – Project Ranking Criteria Rev. 3, August 29, 2002
16
FIGURE 5.
VALIDATION OF PROJECT RANKING PROCESS
Scatter plot of benefit/cost ratio shows high correlation between cost and project ranking
(i.e., project priority is primarily dependent on project cost).
Scatter plot of benefit/log-cost ratio shows a more random pattern
(project ranking is not dependent on project cost alone).
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Ranking (Benefit Points per log$)Project Cost ($ million)