HomeMy Public PortalAboutExhibit MSD 65B - 2005 CDM Wet Weather Flow Cost Allocation Study1
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Metropolitan St. Louis Sewer District
Wet Weather Flow Cost Allocation study
January 2005
� Final Report
1 MSD PN 04-092
CDM PN 20314-43486
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Contents
ISection 1- Introduction
1.1 Background 1-1
I 1.2 Scope of Services and Project Approach 1-2
1.2.1 Background Investigation and Data Collections 1-2
1.2.2 Development of Alternative Allocation Methodologies 1-3
1 1.2.3 Preferred Alternative Development 1-3
1.2.4 Preliminary Report 1-3
1.2.5 Project Completion and Final Report 1-3
1 1.3 Report Organization 1-3
Section 2 - Data Development
1 2.1 Data Collection Summary 2-1
2.1.1 Impervious Area by Customer Class 2-1
1 2.1.2 Inch -Feet of Pipe 2-2
2.2 Wet Weather Flow Analysis 2-2
2.2.1 Wastewater Treatment Plant Analysis 2-2
1 2.3 Data Analysis Limitations 2-7 -
2.4 Sanitary Sewer Overflow Estimates 2-7
Conclusions 2-9
12.5
Section 3 - Wet Weather Volume Cost Allocation Alternatives
1 3.1 Introduction 3-1
3.2 Existing Rate Model Sensitivity Analysis and Wet Weather Cost Allocation
Alternatives 3-2
1 3.2.1 Existing Rate Model Sensitivity Analysis 3-3
3.2.2 Sensitivity Analysis Results 3-5
3.3 Factors Used to Develop Wet Weather Cost Allocation Alternatives 3-13
1 3.3.1 Updated Percentages of Wet Weather Volume to Wastewater
Volume 3-13
3.3.2 Alternative Capacity and Volume Cost Allocation
Methodologies 3-14
3.4 Wet Weather Cost Allocation Alternatives 3-15
1 3.5 Wet Weather Cost Allocation Alternative Evaluations 3-18
3.5.1 Existing Rate Model -Baseline Analysis 3-18
3.5.2 Alternative 2 - 8-Inch-Foot Equivalent Capacity Allocation 3-25
1 3.5.3 Alternative 3 - Capacity Allocation Base on 50-Foot/ 6-Inch
Lateral 3-32
3.6 Conclusion 3-39
CDM
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Section 4 - Allocation Alternative Comparison
4.1 Introduction 4-1
4.2 Revaluation Criteria and Ranking Methodology 4-2
4.2.1 Rate Impact 4-2
4.2.2 Ratemaking Methodology 4-3
4.2.3 Class Equity 4-3
4.2.4 Administrative Simplicity 4-6
4.3 Summary of Criteria Ranking 4-7
Appendix A Wet Weather Flow Analysis Technical Memorandum
Appendix B Billing Summaries
Appendix C Evaluation Matrix Calculations
Appendix D Glossary
CDPA
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I Figures
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2-1 2001-2003 Rainfall at Wastewater Treatment Plants vs. Lambert St. Louis
International Airport 2-4
2-2 Dry Weather Flow vs. Wet Weather Flow Percentage by Service Area 2-5
3-1 MSD Wet Weather Cost Allocation Percent Change From Baseline 3-4
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Preferred Alternative Report
Tables
1 2-1 Impervious Area By Customer Class 2-1
2-2 Length and Equivalent Length of Separate Area and Combined Area
ISewer 2-2
2-3 Wastewater Treatment Plant Wet Weather Analysis Results 2001-2003 2-3
2-4 Wet Weather Analysis Results for Service Areas Analyzed from 2001-2003 2-5
I 2-5 Percent Wet Weather Volume in System 2-6
2-6 Average Annual Volume in Combined Service Areas Z-6
I 2-7 Average Annual Volume in Separate Service Areas 2-7
3-1 MSA Wet Weather Cost Allocation & Rates Status Quo (Base Line) 3-6
3-2 MSD Wet Weather Cost Allocation & Rates Status Quo
I(Base Line) Rate Comparison 3-7
3-3 Alternative B - MSD Wet Weather Cost Allocation & Rates Distribution of
Estimated Wet Weather Flows to Capacity and Volume -100 Percent
of Wet Weather Costs Allocated by Volume Comparative Revenues 3-8
3-4 Alternative B - MSD Wet Weather Cost Allocation & Rates Distribution of
I Estimated Wet Weather Flows to Capacity and Volume 100 Percent of Wet _
Weather Costs Allocated by Volume Comparative Rates 3-9
3-5 Alternative C - MSD Wet Weather Cost Allocation & Rates Distribution of
1 Estimated Wet Weather Flows to Capacity and Volume 100 Percent of Wet
Weather Costs Allocated by Customer/Capacity Comparative
Revenues 3-10
1 3-6 Alternative C - MSD Wet Weather Cost Allocation & Rates Distribution of
Estimated Wet Weather Flows to Capacity and Volume 100 Percent of Wet
1 Weather Costs Allocated by Customer/Capacity Comparative Rates 3-11
3-7 Alternative D - MSD Wet Weather Cost Allocation & Rates 50/50 Split
of Wet Weather Costs to Customer/Capacity and Volume Comparative
11 Revenues 3-12
3-8 Alternative D - MSD Wet Weather Cost Allocation & Rates Distribution
of Estimated Wet Weather Flows to Capacity and Volume 50/50 Split Wet
1 Weather Costs to Customer/Capacity and Volume Comparative Rates 3-13
3-9 MSD Wet Weather Cost Allocation & Rates Update Estimated Wet
1 Weather Flow Percentage Calculation of Weighted Average by
Service Area 3-14
3-10 Alternative 1(a) - MSD Wet Weather Cost Allocation & Rates Update
I Estimated Wet Weather Flow Percentage Comparative Revenue 3-19
3-11 Alternative 1(a) - MSD Wet Weather Cost Allocation & Rates Update
Estimated Wet Weather Flow Percentage Comparative Rates 3-20
1 3-12 MSD Wet Weather Cost Allocation & Rates Distribution of Estimated Wet
Weather Flows to Capacity and Volume Impervious Area by
1 Customer Class 3-21
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Preferred Alternative Report
3-13 Alternative 1(b) - MSD Wet Weather Cost Allocation of Rates Wet Weather
Capacity Allocated by Customer - Volume by Impervious Area
Comparative Revenue 3-22
3-14 Alternative 1(b) - MSD Wet Weather Cost Allocation & Rates Wet Weather
Capacity Allocated by Customer - Volume by Impervious Area
Comparative Rates 3-23
3-15 Alternative 1(c) - MSD Wet Weather Cost Allocation & Rates Wet Weather
Volume & Subsidized Stormwater Costs Distributed by Impervious Area
Comparative Revenue 3-24
3-16 Alternative 1(c) - MSD Wet Weather Cost Allocation & Rates Wet Weather
Volume & Subsidized Stormwater Costs Distributed by Impervious Area
Comparative Rates 3-25
3-17 Alternative 2(a) - MSD Wet Weather Cost Allocation & Rates Distribution
of Estimated Wet Weather Volume to Capacity and Volume Capacity Based
on 8-Inch-feet of System Pipe 3-26
3-18 Alternative 2(a) - MSD Wet Weather Cost Allocation & Rates Distribution
of Estimated Wet Weather Flows to Capacity and Volume Capacity Based
on Minimum 8-Inch-feet of System Pipe Comparative Revenues 3-27
3-19 Alternative 2(a) - MSD Wet Weather Cost Allocation & Rates Distribution
of Estimated Wet Weather Flows to Capacity and Volume Capacity
Based on Minimum 8-Inch-feet of System Pipe Comparative Rates 3-28
3-20 Alternative 2(b) - Capacity Based on Minimum 8-Inch-feet of System Pipe
Wet Weather Capacity Allocated by Customer - Volume by Impervious
Area Comparative Revenues 3-29
3-21 Alternative 2(b) - Capacity Based on Minimum 8-Inch-feet of System Pipe
Wet Weather Capacity Allocated by Customer - Volume by Impervious
Area Comparative Rates 3-30
3-22 Alternative 2.3(c) - MSD Wet Weather Cost Allocation & Rates Wet Weather
Volume & Unfunded Stormwater Costs Distributed by Impervious Area,
8-Inch-foot Pipe Allocation Comparative Revenue 3-31
3-23 Alternative 2.3(d) - MSD Wet Weather Cost Allocation & Rates Wet Weather
Volume & Unfunded Stormwater Costs Distributed by Impervious Area,
Impervious Area Rate Comparison Comparative Rates 3-32
3-24 Alternative 3 - MSD Wet Weather Cost Allocation & Rates Distribution of
Estimated Wet Weather Flows to Capacity and Volume Capacity Based
on 50-Feet of 6-Inch Diameter Laterals 3-33
3-25 Alternative 3(a) - MSD Wet Weather Cost Allocation & Rates Distribution of
Estimated Wet Weather Flows to Capacity and Volume Capacity Based
on 50-Feet of 6-Inch Diameter Laterals Comparative Revenues 3-34
3-26 Alternative 3(a) - MSD Wet Weather Cost Allocation & Rates Distribution of
Estimated Wet Weather Flows to Capacity and Volume Capacity Based
on 50-Feet of 6-Inch Diameter Laterals Comparative Rates 3-35
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Table of Contents
Preferred Alternative Report
3-27 Alternative 3(b) - Capacity Based on 50-Feet of 6-Inch Width Laterals
Comparative Wet Weather Capacity Allocated by Customer - Volume by
Impervious Area Revenue Comparison 3-36
3-28 Alternative 3(b) - Capacity Based on 50-Feet of 6-Inch Width Laterals
Comparative Wet Weather Capacity Allocated by Customer - Volume by
Impervious Area Comparative Rates 3-37
3-29 Alternative 3(c) - MSD Wet Weather Cost Allocation & Rates Wet Weather
Volume & Unfunded Stormwater Costs Distributed by Impervious Area
8-Inch-foot Pipe Allocation Comparative Revenue 3-38
3-30 Alternative 3(c) - MSD Wet Weather Cost Allocation & Rates Wet Weather
Volume & Unfunded Stormwater Costs Distributed by Impervious Area
Impervious Area Rate Comparison 3-39
4.1 Rate Impact Changes to Single Family Bill Standard Deviation and
Evaluation Score 4-2
4-2 Inter -Class Equity Changes to Customer Class Costs Standard Deviation
and Evaluation Score 4-4
4-3 Intra-Class Equity Changes to Customer Class Billings Standard Deviation
and Evaluation Score 46
4-4 Class Equity Evaluation Score Summary 4-6
4-5 Existing Rate Structure and Alternative 1, 37/63 Percent Capacity/Volume
Allocation Wastewater Allocation Alternative Evaluation Matrix 4-8
4-6 Alternative 2 Minimum 8-Inch-Feet of System Pipe - Wastewater Allocation
Alternative Evaluation Matrix 4-9
4-7 Alternative 2 Minimum 8-Inch-Feet of System Pipe - Capacity/Volume
Allocation Wastewater Allocation Alternative Evaluation Matrix 4-10
4-8 Summary of Weighted Alternatives 4-11
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Section 1
Introduction
1.1 Background
The Metropolitan St. Louis Sewer District (MSD) MSD is organized pursuant to
Article VI, Section 30 of the state constitution, which empowers the people of St. Louis
County and the city of St. Louis "to establish a metropolitan district for functional
administration of services common to the area."
MSD was created in 1954 to provide a metropolitan -wide sewer system and in 1956
MSD assumed operations of all publicly owned wastewater and storm drainage
facilities within its originally established service area. This area is commonly referred
to as the original area, including the incorporated area of the City. In 1977, MSD
annexed a 279 square mile area of the lower Missouri River basin and the Meramec
watershed, doubling its service area, and in 1978 purchased the Fee Fee Trunk Sewer
Company and Missouri Bottoms Sewer Company. MSD has continued to expand its
service area since 1978, purchasing several smaller wastewater systems and
expanding services into St. Louis County based on requests for service by residents
and currently services 524 square miles with a population of 1.4 million.
MSD is a publicly owned and non-profit district which is supported by taxes and
various charges levied on persons within its boundaries. MSD's Board of Trustees
was given the authority to levee taxes and charges, in accordance with state laws and
regulations to pay for the services provided by MSD.
In November 2000, the voting public of St. Louis County and City created the Rate
Commission by approving admendments to the MSD's Charter. The Rate
Commission was established to provide a review of MSD rate change proposals and
provide recommendations concerning these rate changes to the Board of Trustees.
The Rate Commission is a group of 15 commissioners representing various ratepayer
constituencies throughout the St. Louis Metropolitan Area. Although the
commissioners are appointed by the MSD's Board of Trustees, the Rate Commission is
defined by Charter as having independent and objective review responsible for all
Rate Changes under consideration by MSD. The Rate Commission established
governing procedures and guidelines for their deliberations which are outlined in the
"Operational Rules, Regulations and Procedures of the Rate Commission."
MSD submitted its first Rate Change proposal to the Rate Commission in May 2002
and revisions to the proposal in April 2003. The Rate Commission issued its rate
recommendation in the Rate Commission Report (May 2003). In this report the Rate
Commission recommended MSD conduct a study to determine the most accurate
allocation and cost recovery method for Infiltration/Inflow (I/I) operation costs, and
requested that the results be presented to the Rate Commission before any future rate
change submittals.
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Section 1
Introduction
MSD issued a request for Proposal (RFP) June 24, 2004, and selected CDM to perform
the requested study. The study will address the six issues discussed in the Rate
Commission's review. These issues are:
1. Wet Weather Flow;
2. Customer Classification;
3. Stormwater Cost Recovery;
4. Changes in Excess Strength Suspended Solids;
5. Additional Working Capital Requirements; and,
6. Resistance Factor
1.2 Scope of Services and Project Approach
In 1993, MSD changed the Inflow/Infiltration (I/I) cost allocation from a 50/50
percent allocation to a 37 percent recovery by the system availability charge and 63
percent by volume recovery charge. There where no studies performed to
substantiate the rationale for the change.
The scope of this study is to investigate and present I/I cost allocation options, and
assess advantages and disadvantages of each option with the goal of determining an
acceptable methodology. Evaluations of the alternatives were based on criteria
established in the Rate Commission Charter for rate reviews. Alternatives considered
the development of rationales for customer and volume cost distribution, including
impervious area and customer classifications, such as residential, commercial and
industrial.
The study was conducted in a series of work phases as described below.
1.2.1 Background Investigation and Data Collections
Data and information needs were determined and collected from MSD. Information
used in the evaluation and determination of alternative cost allocation methodologies
included:
• Daily flow data for each MSD wastewater treatment plant;
• Rainfall data from MSD rain gauges;
• Flow monitoring data from within the collection system;
• Impervious area data for all service areas:
• Collection system data, such as pipe length and diameter, for the entire collection
system;
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Section 1
Introduction
■ Number of accounts in the billing system;
• Billed volume or number of billable units for all accounts;
• Significant industrial user data; and,
■ Influent wastewater strength data at all MSD wastewater treatment plants.
In addition, a review of industry standards and approaches implemented by other
agencies similar to MSD were reviewed to establish wet weather cost allocation
alternatives.
1.2.2 Development of Alternative Allocation Methodologies
Alternative approaches for allocation I/I and wet weather costs were developed and
screened. A cost -causative basis was used to recommend alternatives for further
consideration. A workshop was held with MSD to review the findings and discuss
system data and approaches recommended for determining the wet weather
allocation percentages.
1.2.3 Preferred Alternative Development
The alternatives recommended for evaluation were reviewed in more detail. A
simplified rate evaluation model was developed and tested against the MSD rate
model for accuracy as a tool to evaluate the revenue and cost impacts of each
alternative. A Preferred Alternative Report was developed and distributed to the
project team. A second workshop was conducted to review the results of the
preferred alternative development and refine the evaluation matrix approach.
1.2.4 Preliminary Report
A Preliminary Wet Weather Allocation Report was prepared and distributed to the
project team members. The report focused on the development, analysis and rate and
revenue changes of each alternative. The draft evaluation matrix and ranking criteria
was included in the report. A final workshop was conducted with MSD at which time
the preliminary findings of the study were presented and final comments from
management were gathered.
1.2.5 Project Completion and Final Report
Final revisions to the Wet Weather Allocation report were incorporated and the final
Wet Weather Cost Allocation Report distributed to the project team. Final comments
were received and changes made to the report as appropriate. Information contained
in the final report includes a summary of the support data collected, the wet weather
flow analyses, discussion of the alternatives, the evaluation matrix, and ranking of the
alternatives.
1.3 Report Organization
The report has been organized to present the data collected, its use in the
development of the study, the resulting analyses; the development of alternative
P:120314 MSD 434881.1 Cost Allocation Study\Final ReponU^ectionlliinal.doc
1-3
Section 1
Introduction
methodologies and their associated impacts, and an evaluation matrix based on
defined criterion and analyses results. The information contained in the report
sections and appendices is outlined below:
• Section 1 contains background information on MSD and the Rate Commission, and
discusses the scope and activities conducted for the project.
• Section 2 summarizes the data collected for the study, reviews the methodology
and presents results of the wet weather flow analysis.
• Section 3 defines each alternative evaluated and details the impact of the rate
changes on customer classes.
■ Section 4 presents the evaluation matrix and recommended alternative.
• Section 5 addresses the following additional issues requested by the Rate
Commission: stormwater cost recovery, resistance factor, change in extra strength
suspended solids, and working capital.
• Appendix A contains an analysis of wet weather flow in five sewersheds.
■ Appendix B contains billing summaries for each alternative.
■ Appendix C contains the evaluation matrix calculations.
■ Appendix D contains a Glossary of terms used in the report.
CDM
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Section 2
Data Development
2.1 Data Collection Summary
Data was collected from MSD to develop the alternatives described in Section 3.
Additional analyses that were conducted to assist in data evaluations are contained in
Appendix A. The data collected was used to:
• calculate impervious area by customer class;
• calculate the length of sanitary and combined sewer pipe in all service areas;
• determine percentage of wastewater treated and wet weather flow volume for
each wastewater treatment plant and combined area;
• estimate annual volume of combined sewer overflows; and
• estimate volume of wet weather flow transported bythe collection system.
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2.1.1 Impervious Area by Customer Class
Impervious area data and land use data for St. Louis City and St. Louis County was
provided by MSD in SHAPE' file format and entered into a Geographical Information
System (GIS) database. The impervious area square footage and percentages by
customer class for the billable area are presented in Table 2-1. It is generally accepted
that there is a correlation between stormwater runoff due to impervious area and wet
weather flow. This data was used in Section 3 to calculate wet weather volume costs
based on impervious area.
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Table 2-1
Impervious
Customer Class
Impervious Area
Square Feet
Percent of Total Customer
Class Impervious Area*
Commercial
855,071,716
34.2%
Industrial
314,116,495
12.6%
Single Family Residential
1,111,065,766
44.4%
Multi -Family Residential
220,046,834
8.8%
Total*
2,500,300,011
100%
i SHAPE files are files that contain a set of points,arcs, or polygons that hold tabular data and a spatial
location.
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Section 2
Data Development
Table 2-4
Wet Weather Analysis Results for Service Areas Analyzed from 2001-
Average Annual Contribution
Service Area
Plant Inflow
Volume (MG)
Wet Weather
Volume (MG)
Wet Weather Flow
Percentage (%)
16.6%
Coldwater Creek
9728
1615
Missouri River'
10176
771
7.6%
Lower Meramec
11615
1585
13.6%
Bissell Point
44685
6075
13.6%
River Des Peres
40416
9307
23.0%
Total District
115902
19353
16.7%
es:
1. Does not include October 2001 flow data
Figure 2-2
Dry Weather Flow vs. Wet Weather Flow Percentage by
Service Area
100% — -
90%
80%
70%
60%
50%
40%
30%
20%
10%
0%
--92%
----83%
8%
86%0
14% --
Coldwater Missouri Lower
Creek River* Meramec
86% _ In Dry Wet
Wet
77%
14%
Bissell Point
River Des
Peres
'Does not include October 2001 flow data
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Section 2
Data Development
The highest percent wet weather flow was seen in the River Des Peres Service Area at
23 percent. This percentage is probably low for a combined area such as River Des
Peres because this percentage does not include contribution from combined sewer
overflows (CSOs). Coldwater Creek also had a high percent wet weather flow at 17
percent. Since Coldwater Creek Service Area is a separate sewer system, this
percentage indicates that this area is particularly susceptible to wet weather flow
especially considering that sanitary sewer overflows (SSOs) are excluded from this
analysis.
CSO contribution was added to the total district averages presented in Table 2-4. An
estimate of annual CSO contribution was included in the MSD Capital Improvements
and Replacement Plan Report (SKME, 2002) for Bissell Point Service Area (9.3 billion
gallons [BG]) and River Des Peres Service Area (16.7 BG) resulting in an annual CSO
contribution of 26.6 BG. The values shown below in Table 2-5 combine this CSO
contribution estimate with wastewater treatment plant analysis data presented in
Table 2-4, to calculate the average annual district -wide wet weather contribution of 32
percent.
Table 2-5
2001-2003 Percent Wet W
Average Annual Wet Weather Volume at Treatment Plants
19353 MG
Average Annual Total Volume at Treatment Plants
116,602 MG
Average Annual Combined Sewer Overflow Contribution
26000 MG
Average Annual Wet Weather Volume in System
(CSO + Wet Weather Volume at Treatment Plants)
45353 MG
Average Annual Total Volume in System
(CSO + Total Volume at Treatment Plants)
142620 MG
Percent Wet Weather Volume in System
32 percent
In the combined service areas, the resulting annual percent wet weather volume when
CSOs are considered is 29 percent in the Bissell Point Service Area and 45 percent in
the River Des Peres Service Area. The combined annual wet weather contribution for
the two combined sewer areas is 37 percent as shown in Table 2-6, and the combined
annual wet weather contribution for the three separate service areas are in Table 2-7.
Table 2-6
2001-2003 Avera
Service Area
Average Annual Contribution
Plant
Inflow
Volume
(MG)
CSO
Volume
(MG)
Total Volume
in Combined
Service Area -
Plant Inflow +
CSO (MG)
Wet Weather
Volume at
Plant (MG)
Total Wet Weather
Volume - Wet
Weather at Plant +
CSO (MG)
Bissell
44685
9300
53985
6075
15375
RDP
40416
16700
57116
3907
26007
Total Combined Sewer Areas
85101
26000
110383
15382
41382
Percent Wet Weather Flow 37%
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Section 2
Data Development
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Table 2-7
2001-2003 Average Annual V
Average Annual Contribution
Service Area
Plant Inflow
Volume (MG)
Wet Weather
Volume (MG)
Coldwater Creek
9728
1615
Missouri River'
10176
771
Lower Meramec
11615
1585
Total Separate Service Areas
31519
3971
Percent Wet Weather Flow 13%
1. Does not include October 2001 flow data
In the separate service area, the percent wet weather flow could be higher than 13
percent due to the exclusion of SSOs. However, the CSO estimates assume that all
CSO flow will be captured which could be a conservative estimate and may account
for the unknown SSOs.
The system wide wet -weather flow contribution is estimated as approximately 32
percent, and can be applied for a district -wide rate allocation. However, wet weather
flow contribution varies between sewersheds, combined and separate sewer service
areas, and due to the actual amount of CSOs and SSOs that will be captured for
conveyance/storage and treatment.
1 2.3 Data Analysis Limitations
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The analysis was focused at the wastewater treatment plant level using daily plant
influent data, which provided estimates of service area level wet -weather
contributions. This information is sufficient to evaluate and screen various wet
weather rate evaluation alternatives. Other limitations include:
• SSOs have not been modeled and would increase the wet weather flow
percentage, especially in areas with many bypasses. MSD's sewer models could
be used to simulate annual SSO volumes. This task could be undertaken to
further refine the wet -weather volumes.
• CSO volumes are derived from past analyses for River Des Peres and Bissell Point
Service Areas. The analyses could be further refined with additional information
describing actual CSO capture for treatment.
2.4 Sanitary Sewer Overflow Estimates
Sanitary sewer overflows (SSO) occur in sanitary sewer systems dedicated to the
collection and conveyance of wastewater; and do not combine wastewater with
stormwater. SSOs occur in collection systems for several reasons including blockage,
broken pipes, defects that allow stormwater or groundwater to enter the system, illicit
connection of roof drains and sump pumps, inadequate operation and maintenance,
equipment and power failures and vandalism.
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Section 2
Data Development
MSD's separate collection system contains approximately 320 SSOs. The cost to
monitor and measure sanitary sewer overflows (SSO) in a system with approximately
320 SSO locations would be expensive and difficult to maintain. The typical cost per
meter day for in -pipe flow monitoring equipment is approximately $100 and for one
year, the estimated cost to install, maintain and collect data for the flow monitoring
equipment in each SSO would be $7 to $12 million.
Two approaches have been used to estimate the impact SSO volume could have on
the percentage of wet weather flow compared to wastewater flow collected in MSD
systems.
• Review of EPA estimates of the total volume of SSO attributed to municipal
wastewater collection systems.
• Analysis of how sensitive the percent of wet weather flow to wastewater flow is to
the SSO volume estimate.
EPA Report To Congress: Impact and Control of CSOs and SSOs
In the EPA Report to Congress: Impacts and Control of CSOs and SSOs (published
August 26, 2004) it was determined that there are about 19,000 municipal sanitary
sewer collection system in the United States, discharging between 3 to 10 billion
gallons of wastewater through SSOs. EPA has estimated that 74 percent of the SSO
volume is related to wet weather, inflow and infiltration, and the remaining
attributable to blockages and failures in the collection system.
The report estimates the annual volume of treated wastewater, CSO and SSO. Based
on this data and using a SSO estimate of 10 billion gallons per year, SSOs accounted
for less than 1 percent of average volume discharged in a year, nationwide. The data
contained in this report supports an increase of the system wide wet -weather flow
contribution from 32 percent to 33 percent.
Estimate Based on Inflow and Infiltration Per Foot of Lateral
An estimate of the annual inflow that occurs per foot of private laterals was
developed to test the impact inflow and infiltration could have on the wet weather
volume conveyed by the collection system. This analysis did not attempt to
determine the percentage of the flow entering the lateral that was treated; rather,
assumed all the flow entering the system from laterals was discharged through SSOs
and the wet weather flow treated by the treatment plants was due to inflow and
infiltration occurring in the collection system. If an assumption of 5 to 20 cubic feet
per foot per year of lateral is used to estimate the amount of wet weather volume
entering the system (375 to 7480-gallons per year per typical home with a 50-foot
lateral) and assuming 330,420 customer accounts in the separate collection systems
identified in Table 2-4 (It is assumed that the separate collection systems include 100
percent of the accounts in Meramec, Coldwater Creek and Missouri River Service
Area, 55 percent of accounts in Bissell Point Service Area, and 64 percent of accounts
in River Des Peres Service Area, as identified in the Long Term Control Plan.), a total
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Data Development
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volume of between 620 and 2480 million gallons will be discharged through SSOs.
Including this volume in Table 2-5, would support increasing the percent wet
weather from 32.3 percent to between 32.3 and 33.1 percent.
2.5 Conclusions
The following conclusions from these analyses can be used for the rate option
evaluation:
• Within the service areas, the wet weather flow contribution varied from 13 percent
in the separate area systems to 37 percent in the combined area systems; and,
• The system wide wet -weather flow contribution is estimated as approximately 33
percent and includes an estimate of the volume contributed by SSOs.
These analyses demonstrate that wet weather contribution is variable between each
service area. It is important to consider this when evaluating wet weather flow for
sewer rates. A detailed flow monitoring data analysis and modeling program for wet
weather conditions would be necessary to get an accurate account of wet weather
flows and SSOs from separate service areas.
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Section 3
Wet Weather Volume Cost Allocation
Alternatives
3.1 Introduction
MSD currently maintains a model to update and evaluate its wastewater rates. This
rate model has multiple modules linked together to produce rates and charges for the
current fiscal year and forecasted periods. These modules consist of three essential
components of ratemaking: Revenue Requirement, Cost of Service Allocation and
Rate Structure Development.
This section of the study focuses on the cost allocation and rate structure modules of
the rate model. More specifically, how cost of service is allocated to I/I (wet weather)
flows and how MSD rates are designed to recover those costs from customers. There
are two primary factors that affect the wet weather cost allocation in the existing MSD
rate model. These are:
1. The estimated percentage of wet weather flow to wastewater flow transported by
the collection system; and
2. The distribution of wet weather flows to either capacity or volume charges in the
cost of service allocation.
MSD's current rate model distributes wet weather costs based on a 45/55 percent
estimate of wet weather flow to wastewater flow and a 37/63 percent split between
capacity and volume, respectively.
Changing these primary factors in the rate model will redistribute the costs for wet
weather volume to the established customer classes. For example, if the estimated
percent of wet weather is reduced to 40 percent, this would increase the amount of
costs allocated to the wastewater component of the rate base, increasing the total costs
allocated to the customer class with larger contributed volume. Thus, all other things
being equal, an increase in wet weather will decrease the charges to large volume
customers and increase rates for smaller volume customers.
Likewise a change to the wet weather volume distributed to capacity or changing
distribution of volume cost from billed volume to impervious area would result in an
increase in allocation to customers with larger contributed volumes or impervious
areas.
Presented in this section are the alternatives identified for allocating costs to
customers using these primary factors, as well as several allocation methods for wet
weather volume costs. These alternatives will be evaluated and compared to the
P:120314 MSD143486 I -I Cost Allocation Stuoy.Final RepontSection3tinal.Coc
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Wet Weather Volume Cost Allocation Alternatives
current costs allocated to the established customer classes for wastewater services.
The primary tasks of this section are to:
1. Update the estimated percentage of wet weather flow to wastewater flow
transported by the collection system based on the analysis conducted in
Section 2;
2. Establish the basis for distribution of capacity and volume in the MSD rate
model; and
3. Identify and evaluate alternate cost allocation methodology for wet weather
volume costs.
The results of each of the alternatives will be presented with customer impacts. This
information is used to evaluate the alternatives in Section 4.
3.2 Existing Rate Model Sensitivity Analysis and Wet Weather
Cost Allocation Alternatives
The Financing and Charges for Wastewater Systems Manual (1984) prepared by the
American Public Works Association, American Society of Civil Engineers, and Water
Pollution Control Federation (presently WEF) indicates that the preferred method of
allocation is to identify all points of flow entry and pass the cost of transporting and
treating these flows onto the various classes of customers identified as the cost
causers. Absent the ability to accurately identify the points of flow entry, the costs
should be passed onto all customers, both in relation to the customer's flows and the
total number of customers. Accordingly, MSD's rate model allocates the cost between
the customer's capacity function and the volume function.
What follows herein is a presentation of the alternatives evaluated as part of this
study that are in accordance with generally accepted ratemaking practices. The -
alternatives are divided into two groups. The first group is designed to illustrate the
sensitivity of MSD's wastewater rate to changes in the "Existing Rate Model Results"
(status quo/baseline). The Existing Rate Model Results are determined using the
existing cost allocation methodology and rate structure.
The second group of alternatives has been developed to address the two primary
factors used to distribute wet weather costs to customers in MSD's rate model
(Section 3.1). Each of the Alternatives 1 through 3 in the second group has a
supportable engineering and economic basis, as well as compliance with generally
accepted ratemaking practices.
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Section 3
Wet Weather Volume Cost Allocation Alternatives
3.2.1 Existing Rate Model Sensitivity Analysis
This first group includes the Existing Rate Model results and three baseline
alternatives. The three alternatives represent the range of impacts that a change in the
allocation of wet weather costs between capacity and volume will have on wastewater
rates. These alternatives were only developed to demonstrate MSD's wastewater rate
sensitivity to changing cost allocations applicable to wet weather costs. This first
group of alternatives will neither be ranked nor considered in the criteria ranking
matrix included in Section 4.
When changing the wet weather flows as it relates to the distribution of costs to
capacity or volume, an increase in allocation to capacity (and decrease to volume)
results in a decreased charge to customers (individual) with larger contributed
volumes and an increase to customers with smaller volumes. Logically, a decrease in
capacity will result in an increase in charges to customers with larger volumes.
Several alternatives have been developed in this section that are designed to
demonstrate the range of rate changes that result when allocating all wet weather
costs to either capacity or volume. These alternatives assume that at one end of the
range of rate changes, all wet weather costs will be allocated by distributing
100 percent of the cost to the volume function. In this alternative, all the wet weather
costs will be recovered from customers through the volume charge component of
MSD's current rate structure. This alternative produces significant increases to large
volume customers while the small user is likely to realize a reduction in wastewater
charges.
At the other end of the range is the allocation of all wet weather costs 100 percent to
customer/capacity. In this alternative, the wet weather costs will be recovered from
customers using the System Availability component of MSD's current rate structure.
It assumes that all wet weather costs are related to customers equally regardless of the
size or the demands of the customer. This has a significant impact on the smaller
volume user, increasing their rates.
In addition to these two alternatives a third alternative is presented that allocates wet
weather costs 50/50 between capacity and volume. This alternative was provided to
present the impacts of changes to the existing 37/63 allocation factors.
The alternatives in this first group that make up the sensitivity analysis are identified
as follows:
A. Existing Rate Model - Status Quo/Baseline
• Ratio of wet weather flows to all wastewater flows is 45 percent
• Allocation of wet weather costs to capacity and volume functions is 37/63,
respectively
P: 20314 MSD143486 1.1 Cost Allocation StudlnFinal Repon\$ection36nal.tloo
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Wet Weather Volume Cost Allocation Alternatives
B. 100 Percent Volume
• Allocation of all wet weather costs assuming 100 percent volume
• Wet weather cost will be recovered from customers using the volume
rate.
• Assumes that all wet weather costs are related to customers based on
their billable volume.
C. 100 Percent Capacity
• Allocation of wet weather costs assuming 100 percent capacity function
• Wet weather cost will be recovered from customers using the System
Availability rate component
• Assumes that all wet weather costs are related to customers equally
regardless of the size or the demands of the customer.
D. 50/50 Allocation Capacity/Volume
• Allocation of wet weather costs 50 percent to the volume function and
50 percent to the capacity function.
The detailed results of each of these alternatives will be presented in Section 3.3.
However, as a general overview the range of increases and decreases determined
through this sensitivity analysis is displayed in Figure 3-1 below.
30.0%
20.0°/D
10.0%
0.0%
-10.0% -
-20.0%
-30.0%
-40.0%
Figure 3-1
MSD Wet Weather Cost Allocation
Percent Change from Baseline
100% Volume 100°/
:Cape
city
50/5
d
Volume/Capacity
ci Single family ❑ Multi Family ❑ Non residential
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Section 3
Wet Weather Volume Cost Allocation Alternatives
3.2.2 Sensitivity Analysis Results
CDM prepared a simplified version of MSD's rate model to test the results and
impacts of each alternative. During the sensitivity analysis, the alternative
assumptions were developed using this simplified model and compared to MSD's
Existing Rate Model Results. The findings were presented in Figure 3-1. This graph
displays a range of increases and decreases each customer class would experience if
the wet weather cost allocation was shifted from 100 percent volume to 100 percent
capacity.
The figure illustrates that changing the existing allocation factor from the existing
37/63 to 100 percent volume and 0 percent capacity would increase the large
volume/non-residential customer rates about 17 percent and decrease residential
rates by about 16 percent. On the other hand, changing the existing allocation factor
to 0 percent volume and 100 percent capacity will create a 29 percent decrease in non-
residential rates and a 27 percent increase in residential rates. Since 100 percent is the
most MSD can allocate to either volume or capacity functions, this defines the
maximum range of the impact of the increases and decreases in rates on the various
customer classes that can be expected from changing the wet weather cost allocation
factors.
The initial results of the simplified model were compared to MSD's rate model runs
using the same alternative assumptions. This test was used to confirm the accuracy of
CDM's model. The following is the detailed results of CDM's of the simplified model
runs for the alternatives designed to prepare the sensitivity analysis.
In addition, due to the inclusion of stormwater costs within the wastewater rates, the
wastewater costs were analyzed separately by excluding the stormwater costs from
the analysis. Therefore, the initial results of the simplified model are also presented
with a column that excludes the stormwater costs.
A. Existing Rate Model Results
The alternative Existing Rate Model Results (A) is based on existing rates. Table 3-1
below provides the results of the base line alternative model run. It compares the
revenue expected to be recovered from existing rates with the alternative results.
There is also a comparison of the revenue per customer class that excludes the
stormwater costs.
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Section 3
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Table 3-1
Alternative A
MSD Wet Weather Cost Allocation & Rates
Status Quo (Base Line)
Factors Utilized
Ill Allocation
45%
Capacity
37%
Volume
63%
Revenue Comparison
Existing
Cost of Service
Revision
Percent
Change
Revision
Without
Stormwater
Costs
Percent
Change
Metered Customers
Single Family
$72,704,600
$72,704,762
0%
$66,953,667
-7.9%
Multifamily
19,269,000
19,269,008
0%
17,800,744
-7.6%
Non -Residential:
Anheuser-Busch
7,566,700
7,566,724
0%
7,216,749
-4.6%
All Other
59,601,100
59,600,938
0%
55,636,143
-6.7%
Total
$159,141,400
$159,141,432
$147,607,303
UnMetered Customers -
Single Family
$16,871,000
$16,870,981
0%
$15,545,875
-7.9% '
Multi Family
10,327,500
10,327,489
0%
9,529,124
-7.7%
Total
$27,198,500
$27,198,470
$25,074,999
Total System
Single Family
$89,575,600
$89,575,743
0%
$82,499,542
-7.9%
Multifamily
29,596,500
29,596,498
0%
27,329,868
-7.7%
Non -Residential
67,167,800
67,167,662
0%
62,852,893
-6.4%
Total System
$186,339,900
$186,339,902
_
$172,682,302
Since the existing rate revenue and alternative rate revenue is the same there is no
change in the Percent Change column. However, for the alternative that excludes the
stormwater costs, the percent change in revenue per customer class is presented.
Table 3-2 presents the existing fee structure and rates, for with and without the
stormwater costs.
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Table 3-2
Alternative A
MSD Wet Weather Cost Allocation & Rates
Status Quo (Base Line) Rate Comparison
Ill Allocation
45%
Capacity
37%
Volume
63%
Rate Comparison
Existing Cost of
Service
Revision
Percent
Change
Revision Without
Stormwater Costs
Percent Change
Billing and Collection Charge/Bill
$1.14
$1.14
0%
$1.14
0%
System Availability Chare/Silt
$6.50 1 $6.50
0%
$5.84
-10.0%
Compliance Charge/Bill
$11.35
$11.35
0%
$11.35
0%
Volume Charge $/Ccf
$1.66
$1.66
0%
$1.52
-8.6%
Typical Residential Bill — 8 Ccf/Month
$20.92
$20.92
0%
$19.14
-8.6%
B. Allocation Based on 100 Percent Volume
Alternative B eliminates the allocation of wet weather flow costs to
customer/capacity. It assumes all wet weather related costs should be recovered
based on customer's billable volume.
Table 3-3 provides the revenues derived from existing rates compared to estimated
revenues determined using the allocation factors for this alternative. Table 3-3 also
presents the revenues required per customer class with stormwater costs excluded.
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Table 3-3
Alternative B
MSD Wet Weather Cost Allocation & Rates
Distribution of Estimated Wet Weather Flows to Capacity and Volume
100 percent of Wet Weather Costs Allocated by Volume Comparative Reve
Factors Utilized
�VJ
Ill Allocation
45%
Capacity
0%
Volume
100%
Revenue Comparison
Existing
Cost of
Service
Revision
Percent
Change
Revision
Without
Stormwater
Costs
Percent
Change
Metered Customers
Single Family
$72,704,600
$60,478,076
-16.8%
$55,957,749
-23.0%
Multifamily
19,269,000
21,831,140
13.3%
20,104,966
4.3%
Non -Residential:
Anheuser-Busch
7,566,700
8,700,341
15.0%
8,236,253
8.8%
All Other
59,601,100
69,803,900
17.1%
64,812,049
8.7%
Total
$159,141,400
$160,813,457
$149,111,017
UnMetered Customers
Single Family
$16,871,000
$15,010,971
-11.0%
$13,873,099
-17.8%
Multi Family
10,327,500
10,515,474
1.8%
9,698,187
-6.1%
Total
$27,198,500
$25,526,446
$23,571,285
Total System
Single Family
$89,575,600
$75,489,047
-15.7%
$69,830,848
-22.0%
Multifamily
29,596,500
32,346,614
9.3%
29,803,153
0.7%
Non -Residential
67,167,800
78,504,241
16.9%
73,048,301
8.8%
Total System
$186,339,900
$186,339,902
$172,682,302
This alternative creates significant shifts in revenue derived from various customer
classes. The single family customers will see a sharp decrease while the non-
residential customers will have an increase. With stormwater costs excluded, there is
a greater decrease shown for single family customers and a smaller increase for non-
residential customers.
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Table 3-5
Alternative C
MSD Wet Weather Cost Allocation & Rates
Distribution of Estimated Wet Weather Flows to Capacity and Volume
100 Percent of Wet Weather Costs Allocated by Customer/Capacity Comparative
Factors Utilized
vvv
Ill Allocation
45%
Capacity
100%
Volume
0%
Revenue Comparison
Existing
Cost of
Service
Revision
Percent
Change
Revision
Without
Stormwater
Costs
Percent
Change
Metered Customers
Single Family
$72,704,600
$93,523,140
28.6%
$85,676,413
17.8%
Multifamily
19,269,000
14,906,499
-22.6%
13,877,377
-28.0%
Non -Residential:
Anheuser-Busch
7,566,700
5,636,468
-25.5%
5,480,797
-27.6%
All Other
59,601,100
42,228,329
-29.1%
40,012,306
-32.9%
Total
$159,141,400
$156,294,437
$145,046,892
UnMetered Customers
Single Family
$16,871,000
$20,038,039
18.8%
$18,394,130
9.0%
Multi Family
10,327,500
10,007,427
-3.1
9,241,280
-10.5%
Total
$27,198,500
$30,045,465
$27,635,410
Total System
Single Family
$89,575,600
$113,561,179
26.8%
$104,070,542
16.2%
Multifamily
29,596,500
24,913,926
-15.8%
23,118,657
-21.9%
Non -Residential
67,167,800
47,864,798
-28.7%
45,493,103
-32.3%
Total System
$186,339,900
$186,339,902
$172,682,302
As one would expect, there is a swing in inequity the opposite of that found in
Alternative 4. With this alternative, the single family will share the majority of the
revenue increase, while the non-residential customer will have a significant decrease.
The revenue requirement for single family decreases without the stormwater costs,
decreasing the impact of a rate increase and the decrease in non-residential customer
rates was greater.
Table 3-6 presents the rate changes affected by this alternative.
CDM
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Table 3-6
Alternative C
MSD Wet Weather Cost Allocation & Rates
Distribution of Estimated Wet Weather Flows to Capacity and Volume
100 percent of Wet Weather Costs Allocated by Customer/Capacity Comparati
Factors Utilized
v
I/I Allocation
45%
Capacity
100%
Volume
0%
Rate Comparison
Existing Cost of Service
Revision
Percent
Change
Revision
without
Stormwater
Costs
Percent
Change
Billing and Collection Charge/Bill
$1.14
$1.14 0%
$1.14
0%
System Availability Charge/Bill
_
$6.50
$17.56 170%
$15.80
143%
Compliance Charge/Bill
$11.35
$11.35 0%
$11.35
0%
Volume Charge $/Ccf
$1.66
$0.96 -42%
$0.91
-45.4%
Typical Residential Bill -8 Ccf/Month
$20.92
$26.38
26%
$24.18
15.61%
There is a significant increase in the System Availability Charge and a large decrease
in the uniform volume rate. If this alternative were implemented, the typical
customer could expect to see a 26 percent increase in monthly charges.
D. Allocation Based on 50/50 Volume/Capacity
Alternative D assumes all the wet weather costs will be recovered from customers
using both the customer/capacity and volume rate equally. It assumes that wet
weather costs are related equally to customers and the demands of the customer.
Table 3-7 presents the revenue impact resulting from changing the estimated wet
weather flow distributed by the 37/63 split to capacity and volume, respectively, to 50
percent customer/capacity and 50 percent volume. Table 3-7 also presents the
revenues required per customer class with stormwater costs excluded.
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Alternative D
MSD Wet Weather Cost Allocation & Rates
Distribution of Estimated Wet Weather Flows to Ca acit
Factors Utilized
Ill Allocation
45%
Capacity
50%
Volume
50%
Revenue Comparison
Existing
Cost of
Service
Revision
Percent
Change
Revision
Without
Stormwater
Costs
Percent
Change
Metered Customers
Single Family
$72,704,600
$77,000,606
5.9%
$70,817,079
-2.6%
Multifamily
19,269,000
18,368,814
-4.7%
16,991,166
-11.8%
Non -Residential:
Anheuser-Busch
7,566,700
7,168,408
-5.3%
6,858,528
-9.4%
All Other
59,601,100
56,016,109
-6.0%
52,412,172
-12.1%
Total
$159,141,400
$158,553,938
$147,078,946
UnMetered Customers
Single Family
$16,871,000
$17,524,509
3.9%
$16,133,618
-4.4%
Multi Family
10,327,500
10,261,455
-0.6%
9,469,738
-8.3%
Total
$27,198,500
$27,785,964
$25,603,356
Total System
Single Family
$89,575,600
$94,525,116
5.5%
$86,950,698
-2.9%
Multifamily
29,596,500
28,630,269
-3.3%
26,460,904
-10.6%
Non -Residential
67,167,800
63,184,518
-5.9%
59,270,701
-11.8%
Total System
$186,339,900
$186,339,902
$172,682,302
This alternative demonstrates that even a small change in the existing distribution of
wet weather costs between capacity and volume can have a moderate affect on
revenue derived from different classes of customers.
Table 3-8 presents the rate changes affected by this alternative.
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Wet Weather Volume Cost Allocation Alternatives
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Table 3-8
Alternative D
MSD Wet Weather Cost Allocation & Rates
Distribution of Estimated Wet Weather Flows to Capacity and Volume
50/50 Split Wet Weather Costs to Customer/Capacity and Volume Com arativ
Factors Utilized
I/I Allocation
45%
Capacity
50%
Volume
50%
Rate Comparison
Existing Cost of Service
Revision
Percent
Change
Revision
without
Stormwater
Costs
Percent
Change
Billing and Collection Charge/Bill
$1.14
$1.14 0%
$1.14
0%
System Availability Charge/Bill
$6.50
$8.78 36%
$7.90
21.5%
Compliance Charge/Bill
$11.35
$11.35 0%
$11.35
0%
Volume Charge $/Ccf
$1.66
$1.50 -10%
$1.39
-16.17%
Typical Residential Bill - 8 Ccf/Month
$20.92
$21.64
5%
$20.17
-3.58%
3.3 Factors Used to Develop Wet Weather Cost
Allocation Alternatives
Alternatives and updates to MSD's existing wet weather cost allocation methodology
were identified and used to develop the second group of alternatives. These
alternatives focus on the development of alternative methodologies for allocating
costs in the capacity and volume ratemaking properties of the rate model.
In all of these alternatives, (with the exception of the Existing Rate Model Status Quo
Alternative), the percentage of wet weather flow to wastewater flow was updated to
33 percent based on the data and analysis presented in Section 2 and Appendix A.
3.3.1 Updated Percentages of Wet Weather Volume to Wastewater
Volume
The estimated percentage of wet weather flows, including CSO and SSO flow
estimates (Section 2) were updated as part of this study. The updated percentage of
wet weather flows is based on sampled actual flows to wastewater treatment facilities
in all five of MSD's service areas.
Table 3-9 displays the calculation of the updated wet weather flow percentage. This
calculation is revised based on sampled data from MSD's wastewater facilities and the
MSD Capital Improvement s and Replacement Plan Report (SKME 2002).
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MSD Wet Weather Cost Allocation & Rates
Update Estimated Wet Weather Flow Percentage
Calculation of Weighted Average by Service Area
Average
Annual
CSO
Total
Wet
Total
Combination
of
Flow
Volume
Flow
Weather
% Wet
Wet Weather
(mg)
(mg)
(mg)
Flow (mg)
Weather
Flow
Coldwater Creek
9,728
9,728
1,615
16.6%
1.1%
Missouri River
10,176
10,176
771
7.6%
0.5%
Lower Meramec
11,615
11,615
1,585
13.6%
1.1%
Bissell Point
44,685
9,300
53,985
15,375
28.9%
10.8%
River Des Peres
40,416
16,700
57,116
26,007
45.5%
18.3%
Total
116,620
26,000
142,620
45,353
32.0%
32.0%
The 32 percent represents all wet weather flow weighted by service area including
estimated CSO flows from combined areas. In consideration of SSO wet weather flow
an estimated 1 percent was added, as discussed in Section 2.4 of this report. Although
SSOs have not been monitored, it is generally accepted that there will be some wet weather flows that should be attributed to the SSO.
All alternatives considered in the final analysis (Section 4), will use 33 percent to
determine the ratio of wet weather flows to total system flows.
3.3.2 Alternative Capacity and Volume Cost Allocation
Methodologies
Several allocation methodologies have been identified for distribution of capacity and
volume costs to each customer class. These alternatives have been used both
individually and in combination to develop the Wet Weather Cost Allocation
Alternatives. Descriptions of the allocation methodologies used to develop the
capacity and volume cost allocation functions are described below.
Capacity Allocations
A. Allocation to capacity based on the existing rate model allocation percentage.
The existing rate model allocates costs to the capacity function of the model
based on a 37 percent allocation to capacity and 63 percent allocation to volume
charge function of the rate model.
B. Allocation to capacity by inch -foot length of pipe assuming 8 inch pipe is
minimum capacity size for the system and is required to serve all customers.
Since wet weather flow is related to inch -feet (or inch -mile) of collection system
pipe, the distribution of costs to capacity will be based on the equivalent
L'M
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P:V0314 MSDW34$61.1 Cost Allocation Study,Final Rcpo,iScction3tna1 doc
Section 3
Wet Weather Volume Cost Allocation Alternatives
minimum 8-inch-foot pipe for the entire length of the systems. The volume
allocation will be based on pipe diameter in excess of 8-inches.
C. Allocation to capacity by lateral inch -foot length assumes 50-foot laterals for all
customer connections and a 6-inch diameter. As with the previous alternative,
since wet weather flow is related to inch -feet (or inch -mile) of collection system
pipe, the distribution of capacity costs will be based on an estimate of the
percentage of 50-foot, 6-inch diameter laterals for all customer connections
divided by total system inch -foot length plus the inch -feet for laterals2. The
percentage represented by the balance of the inch -foot length of the system will
be used to allocate costs to volume.
Volume Cost Allocation
A. Billed Volume - distributes costs to the volume function of the rate model
based on the uniform charge per Ccf for all billable volume. City accounts that
are based on plumbing attributes have been included in the Ccf volume using
unit volumes developed in the MSD rate study.
B. Impervious area charge - This item was developed as an alternative to the rate
structure currently used by MSD. This change adds a new rate component to
the rate structure - charging the wet weather costs allocated to 3the volume -
function based on the impervious area of the customer's property.
Impervious area charges assume that the customer responsibility for wet
weather costs is based on property use and impervious area. This rate
methodology is a generally accepted fee structure for recovering storm water
costs. This alternative recognizes that there is a correlation between storm
water runoff and wet weather flows and passes the cost onto MSD customers
accordingly.
3.4 Wet Weather Cost Allocation Alternatives
The list of alternatives evaluated and ranked by CDM for this study is as follows:
Alternative 1- Existing Rate Model - Baseline Analysis
The existing rate model is used to distribute cost to each customer class based on the
established methodology and percentage allocation between capacity and volume
functions. These alternatives will provide a baseline to allow the reader to determine
the changes in rates to each customer class using the existing capacity and volume
function percentage. The changes to the model functions and cost centers used in
each of Alternative 1 options are presented below:
Inch -feet of pipe as used here means the pipe diameter selected of 8-inches times the linear feet of pipe
in the system.
2 Lateral lengths are not recorded by MSD, thus the estimate of lateral length is added to the recorded
pipe length provided by MSD for the study. A lateral is assumed to be equal to 300 inch -feet (50-foot
length times 6-inch diameter).
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Section 3
Wet Weather Volume Cost Allocation Alternatives
Alternative 1(a) - Updated Estimated Wet Weather Volume Percentage
• The ratio of wet weather flows to wastewater volume is updated to 33
percent;
• Allocation of wet weather costs to capacity and volume functions is 37/63
percent, respectively;
• Volume Costs are distributed to each customer class based billed on
volume (Ccf).
Alternative 1(b) - Volume by Impervious Area
• The ratio of wet weather flows to wastewater volume is updated to 33
percent;
• Allocation of wet weather costs to capacity and volume functions is 37/63
percent, respectively;
• Volume Costs are recovered based on impervious area (square feet) of
each customer class.
Alternative 1(c) - Wet Weather Volume & Subsidized Stormwater Costs Distributed
by Impervious Area
• The ratio of wet weather flows to wastewater volume is updated to 33
percent;
• Allocation of wet weather costs to capacity and volume functions is 37/63
percent, respectively;
• Volume Costs are recovered based on impervious area (square feet) from
each customers class;
• Stormwater cost subsidized by wastewater rates are included in the
volume costs and recovered based on impervious area of each customer
class.
Alternative 2 - Capacity Based on Minimum 8-Inch-Feet of System Pipe
This alternative is based on 8-inch and smaller pipe established as the minimum
capacity size for the system and is required to collect flow from all customers. Since
wet weather flows is related to inch -feet (or inch -mile) of collection system pipe, the
distribution to capacity will be based on the equivalent minimum 8-inch-foot pipe for
the entire length of the system. The volume allocation will be based on pipe width in
excess of 8-inch pipe.
Alternative 2(a) - Capacity Based on Minimum 8 inch -feet of System Pipe Volume
by Billed Volume
• The ratio of wet weather flows to wastewater volume is updated to 33
percent;
• Allocation of wet weather costs to capacity and volume functions based
on 8-inch-feet of system pipe is 60/40 percent, respectively;
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Section 3
Wet Weather Volume Cost Allocation Alternatives
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• Volume Costs are distributed to teach customer class based on billed
volume.
Alternative 2(b) - Capacity Based on Minimum 8 inch -feet of System Pipe, Volume
by Impervious Area
• The ratio of wet weather flows to wastewater volume is updated to 33
percent;
• Allocation of wet weather costs to capacity and volume functions based
on 8-inch-feet of system pipe is 60/40 percent, respectively;
• Volume Costs are recovered based on impervious area of each customers
class.
Alternative 2(c) - Wet Weather Volume & Subsidized Stormwater Costs Distributed
by Impervious Area
• The ratio of wet weather flows to wastewater volume is updated to 33
percent;
• Allocation of wet weather costs to capacity and volume functions based
on 8-inch-feet of system pipe is 60/40 percent, respectively;
• Volume Costs are recovered based on impervious area from each
customers class;
• Stormwater cost subsidized by wastewater rates are included in the
volume costs and recovered based on impervious area of each customer
class.
Alternative 3 - Allocation to Capacity by Inch -foot Length of Pipe and Lateral
Connection
This alternative builds on the definition of the infrastructure required to serve all
customers as discussed in Alternative 2 above, but is expanded to include laterals3 for
all customer connection. As with the previous alternative, this alternative is based on
defining the infrastructure required to collect flow from all customers. Wet weather
flows is related to inch -feet (or inch -mile) of collection system pipe, the distribution of
capacity costs will be based on an estimate percentage of 50-foot long, 6-inch laterals
for all customer connections divided by total system inch -foot length plus the inch -
foot for laterals4. The percentage represented by the balance of the inch -foot length of
the system will be used to allocate costs to volume.
Alternative 3(a) - Capacity Based on 50-Feet of 6-Inch Diameter Laterals
• The ratio of wet weather flows to wastewater volume is updated to 33
percent;
• Allocation of wet weather costs to capacity and volume functions based
on 8-inch-feet of system pipe is 24/76 percent, respectively;
° It is CDM's understanding that laterals are not recorded by MSD: thus the estimate of laterals is added
to the recorded pipe length provided by MSD for the study.
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Section 3
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• Volume Costs are distributed to teach customer class based on billed
volume.
Alternative 3(b) - Capacity Based on Minimum 8-inch-feet of System Pipe, Volume
by Impervious Area
• The ratio of wet weather flows to wastewater volume is updated to 33
percent;
• Allocation of wet weather costs to capacity and volume functions based
on 8-inch-feet of system pipe is 24/76 percent, respectively;
• Volume Costs are recovered based on impervious area of each customers
class.
Alternative 3(c) - Wet Weather Volume & Subsidized Stormwater Costs Distributed
by Impervious Area
• The ratio of wet weather flows to wastewater volume is updated to 33
percent;
• Allocation of wet weather costs to capacity and volume functions based
on 8-inch-feet of system pipe is 24/76 percent, respectively;
• Volume Costs are recovered based on impervious area from each
customers class;
• Stormwater cost subsidized by wastewater rates are included in the
volume costs and recovered based on impervious area of each customer
class.
The revenue distribution and rate for each customer class is evaluated for each of
these alternatives in Section 3.5. These alternatives are further evaluated and ranked
based on specific criteria which is presented in Section 4.
3.5 Wet Weather Cost Allocation Alternative
Evaluations
The simplified rate model developed for this study was completed; the CDM mock
model was used to produce results from the second group of alternatives. These
results were used as input in the final ranking matrix (Section 4).
3.5.1 Existing Rate Model - Baseline Analysis
The detailed alternative analysis is as follows.
Alternative 1(a) - Existing Rate Model - Update Estimate Wet Weather Volume
This alternative updates the ratio of wet weather flow to total system flow from 45
percent to 33 percent as discussed in Section 3.2.
Table 3-10 presents the revenue derived from each customer class using this update.
This table displays the impact of the reduction from the existing 45 percent of flow
applicable to wet weather flow to 33 percent. Table 3-10 also presents the revenues
CDM
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Section 3
Wet Weather Volume Cost Allocation Alternatives
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required per customer class with stormwater costs excluded. In order to present the
wastewater system costs separately, the column "Revision Without Stormwater Costs"
does not include $13,657,602 in stormwater system costs.
Table 3-10
Alternative 1(a)
MSD Wet Weather Cost Allocation & Rates
Updated Estimated Wet Weather Flow Percentage Compa
Factors Utilized
v v —
Ill Allocation
33%
Capacity
37%
Volume
63%
Revenue Comparison
Existing
Cost Of
Service
Revision
Percent
Change
Revision
Without
Stormwater
Costs
Percent
Change
Metered Customers
Single Family
$72,704,600
$70,208,774
-3.4%
$64,681,062
-11.0%
Multifamily
19,269,000
19,742,623
2.5%
18,227,548
-5.4%
Non -Residential:
Anheuser-Busch
7,566,700
7,911,588
4.6%
7,540,902
-0.3% _
All Other
59,601,100
61,644,479
3.4%
57,493,275
-3.5%
Total
$159,141,400
$159,506,180
$147,942,787
UnMetered Customers
Single Family
$16,871,000
$16,482,964
-2.3%
$15,191,840
-10.0%
Multi Family
10,327,500
10,349,471
0.2%
9,547,671
-7.6%
Total
$27,198,500
$26,833,716
$24,739,511
Impervious Area Charges
Single Family
Multifamily
Non -Residential:
Anheuser-Busch
All Other
Total
Total System
Single Family
$89,575,600
$86,691,738
-3.2%
$79,872,902
-11.0%
Multifamily
29,596,500
30,092,094
1.7%
27,775,219
-6.2%
Non -Residential
59,601,100
61,644,479
3.4%
57,493,275
-3.5%
Anheuser-Busch
7,566,700
7,911,588
Total System
$186,339,900
$186,339,896
4.6%
$172,682,298
-0.3%
There is a slight shift of the revenue requirement from residential customers onto non-
residential customers with this alternative. As the costs allocated to wet weather
decline, more costs are allocated to the base wastewater volume rate. Larger volume
customers carry the heavier burden of cost recovery in this wastewater rate structure.
CDM
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Section 3
Wet Weather Volume Cost Allocation Alternatives
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Table 3-11 presents the rate changes affected by this alternative.
Table 3-11
Alternative 1(a)
MSD Wet Weather Cost Allocation & Rates
Update Estimated Wet Weather Flow Percentage Comp
Factors Utilized
I/I Allocation
33%
Capacity
37%
Volume
63%
Rate Comparison
Existing Cost Of Service
Revision
Percent
Change
Revision
without
Stormwater
Costs
Percent
Change
Billing and Collection Charge/Bill
$1.14
$1.14 0%
$1.14
0%
System Availability Charge/Bill
$6.50
$5.22 -19%
$4.68
-28%
Compliance Charge/Bill
$11.35
$11.35 0%
$11.35
0%
Volume Charge $/Ccf
$1.66
$1.72 3%
$1.59
-4.2%
Impervious Area Charge $/Sq.Ft.
$0.0000
$0.0000
Typical Residential Bill - 8 Ccf/Month
$20.92
$20.12
-3.8%
$18.54
-11.4%
Typical Residential Impervious Area Fee
$0.00
This is the simplest of all alternatives to implement and to support. It provides
increased accuracy to the cost of wet weather flow as a percentage of total system cost
in MSD rates.
Alternative 1(b) - Wet Weather Volume Costs Recovered Using Impervious Area
Charge
Table 3-12 displays the total impervious area recorded in all five of MSD's service
areas separated into customer class. This includes residential (including multi family)
and non-residential (commercial and industrial).
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Section 3
Wet Weather Volume Cost Allocation Alternatives
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Table 3-12
MSD Wet Weather Cost Allocation & Rates
Distribution of Estimated Wet Weather Flows to Capacity and Volume
Impervious Area by Customer Class
Impervious Area
(Acres)
% Impervious
Commercial
19,630
34.2%
Industrial
7,088
12.4%
Multifamily
5,052
8.8%
Single Family
25,507
44.4%
Anheuser-Busch
122
0.2%
Total
57,399
100.0%
Using this distribution methodology will require a change in MSD's existing rate
structure. This rate structure includes a charge per residential equivalent impervious
area unit (equal to the average impervious area for a single family residence). The
charges will be separate from and in addition to the wastewater rates.
The basis for this alternative is the establishment of a clear relationship between wet
weather flows (stormwater flows), and the allocation of the costs of handling these
flows onto customers. As stated earlier there is a correlation of wet weather flows to
impervious area. This distribution methodology attempts to capture that relationship
and charge customers accordingly.
In this alternative, the volume component of the wet weather cost is recovered using
an impervious area charge. Table 3-13 displays the comparison of anticipated
revenues from existing rates with the estimated revenues derived from existing rates
plus the impervious area rates. Table 3-13 also presents the revenues required per
customer class with stormwater costs excluded. In order to present the wastewater
system costs separately, the column "Revision Without Stormwater Costs" does not
include $13,657,602 in stormwater system costs.
COM
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Section 3
Wet Weather Volume Cost Allocation Alternatives
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Table 3-13
Alternative 1(b)
MSD Wet Weather Cost Allocation & Rates Wet Weather Capacity
Allocated by Customer - Volume by Impervious Area Comparative Rev
Factors Utilized
-
I/I Allocation
33%
Capacity
37%
Volume
63%
Revenue Comparison
Existing
Cost Of
Service
Revision
Percent
Change
Revision
Without
Stormwater
Costs
Percent
Change
Metered Customers
Single Family
$72,704,600
$52,416,968
-27.9%
$48,715,495
-33.0%
Multifamily
19,269,000
15,027,236
-22.0%
13,996,172
-27.4%
Non -Residential:
Anheuser-Busch
7,566,700
6,059,913
-19.9%
5,879,293
-22.3%
All Other
59,601,100
47,059,278
-21.0%
44,405,171
-25.5%
Total
$159,141,400
$120,563,395
$112,996,130
UnMetered Customers
Single Family
$16,871,000
$12,354,400
-26.8%
$11,487,053
-31.9%
Multi Family
10,327,500
7,822,191
-24.3%
7,279,803
-29.5%
Total
$27,198,500
$20,176,591
$18,766,856
Impervious Area Charles
Single Family I
$20,263,363
$18,183,431
Multifamily
4,013,164
3,601,233
Non -Residential:
Anheuser-Busch
98,362
88,151
All Other
21,323,387
19,046,498
Total
$45,599,913
$40,919,313
Total System
Single Family
$89,575,600
$85,034,731
-5.1%
$78,385,979
-12.5%
Multifamily
29,596,500
26,862,591
-9.2%
24,877,208
-15.9%
Non -Residential
59,601,600
68,382,665
14.7%
63,451,669
6.5%
Anheuser-Busch
7,566,700
6,158,275
-18.6%
5,967,444
-21.1%
Total System
$186,339,900
$186,339,896
-18.6%
$172,682,299
Note that the there appears to be a significant decrease in revenue from all classes of
customers in the metered and unmetered categories. This reflects the shifting of
revenue from the wastewater rates to the impervious area charge. The actual affect of
this alternative is presented under Total System. Non-residential would be expecting
a ten percent increase and the other classes of customers would realize a decrease.
Table 3-14 presents the existing and alternative rates as well as the estimated impact
this alternative will have on typical single family residential bills.
OEM
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Section 3
Wet Weather Volume Cost Allocation Alternatives
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Table 3-14
Alternative 1(b)
MSD Wet Weather Cost Allocation & Rates Wet Weather Capacity
Allocated by Customer -Volume by Impervious Area Comparative R-
Factors Utilized
4w.
I/I Allocation
33%
Capacity
37%
Volume
63%
Rate Comparison
Existing Cost Of Service
Revision
Percent
Change
Revision
without
Stormwater
Costs
Percent
Change
Billing and Collection Charge/Bill
$1.14
$1.14
0%
$1.14
0%
System Availability Charge/Bill
$6.50
$5.22
-19%
$4.69
-27.99%
Compliance Charge/Bill
$11.35
$11.35
0%
$11.35
0%
Volume Charge $/Ccf
$1.66
$1.17
-30%
$1.10
-33.95
Impervious Area Charge $/Sq.Ft.
$0.0183
$0.0164
Typical Residential Bill - 8 Ccf/Month
$20.92
$15.72
-25%
$14.63
-30.25%
Typical Residential Impervious Area Fee
$3.80
$3.41
Alternative 1(c) - Wet Weather Volume and Subsidized Stormwater Costs -
Impervious Area
This alternative is the same as Alternative 1(b) but includes the portion of stormwater
costs subsidized by the wastewater rates. Table 3-15 presents the comparison of
anticipated revenues from existing rates with the estimated revenues revised from
existing rates plus the impervious area rates. Table 3-15 also presents the revenues
required per customer class with stormwater costs excluded. In order to present the
wastewater system costs separately, the column "Revision Without Stormwater
Costs" does not include $13,657,602 in stormwater system costs.
C'DM
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Section 3
Wet Weather Volume Cost Allocation Alternatives
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Table 3-15
Alternative 1(c)
MSD Wet Weather Cost Allocation & Rates Wet Weather Volume & Subsidized
Stormwater Costs Distributed by Impervious Area Comparative Revenue
Factors Utilized
Ill Allocation
33%
Capacity
37%
Volume
63%
Revenue Comparison
Existing
Cost Of
Service
Revision
Percent
Change
Revision
Without
Stormwater
Costs
Percent
Change
Metered Customers
Single Family
$72,704,600
$48,715,495
-33.0%
$48,715,495
-33.0%
Multifamily
19,269,000
13,996,172
-27.4%
13,996,172
-27.4%
Non -Residential:
Anheuser-Busch
7,566,700
5,879,293
-22.3%
5,879,293
-22.3%
All Other
59,601,100
44,405,171
-25.5%
44,405,171
-25.5%
Total
$159,141,400
$112,996,130
$112,996,130
UnMetered Customers
Single Family
$16,871,000
$11,487,053
-31.9%
$11,487,053
-31.9%
Multi Family
10,327,500
7,279,803
-29.5%
7,279,803
-29.5%
Total
$27,198,500
$18,766,856
$18,766,856
Impervious Area Charges
Single Family
$24,252,498
$18,183,431
Multifamily
4,803,213
3,601,233
Non -Residential:
Anheuser-Busch
117,176
88,151
All Other
25,404,026
19,046,498
Total
$54,576,913
40,919,313
Total System
Single Family
$89,575,600
$84,455,045
-5.7%
$78,385,979
-12.5%
Multifamily
29,596,500
26,079,188
-11.9%
24,877,208
-15.9%
Non -Residential
59,601,100
69,809,197
+17.1%
63,451,669
6.5%
Anheuser-Busch
7,566,700
5,996,469
-20.8%
5,967,444
-21.1%
Total System
$186,339,900
$186,339,896
$172,682,299
This has the affect of increasing rate revenue slightly more for non-residential
customers compared to Alternative 1(b). A part of this increase comes from the
updated percentage of wet weather flows which decreased the percent from 45 to 33.
CNA
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Section 3
Wet Weather Volume Cost Allocation Alternatives
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Table 3-16 presents the existing and alternative rates as well as the estimated impact
this alternative will have on typical single family residential bills.
Table 3-16
Alternative 1(c)
MSD Wet Weather Cost Allocation & Rates Wet Weather Volume & Subsidized
Stormwater Costs Distributed by Impervious Area Comparative Rates
Factors Utilized
Ill Allocation
33%
Capacity
37%
Volume
63%
Rate Comparison
Existing Cost Of Service
Revision
Percent
Change
Revision
without
Stormwater
Costs
Percent
Change
Billing and Collection Charge/Bill
$1.14
$1.14
0%
$1.14
0%
System Availability Charge/Bill
$6.50
$4.69
-28%
$4.69
-28%
Compliance Charge/Bill
$11.35
$11.35
0%
$11.35
0%
Volume Charge $/Ccf
$1.66
$1.10
-34%
$1.10
-33.95
Impervious Area Charge $/Sq.Ft.
$0.0218
$0.0164
Typical Residential Bill - 8 Ccf/Month
$20.92
$14.63
-30.1%
$14.63
-30%
Typical Residential Impervious Area Fee
$4.55
$3.41
3.5.2 Alternative 2 - 8-Inch-Foot Equivalent Capacity Allocation
Table 3-17 presents the total inch -feet of collection system recorded by MSD for both
sanitary and combined systems (Section 2.1.2). CDM has calculated the equivalent 8-
inch-foot of pipe based on this information and determined a customer/capacity
allocation factor.
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Section 3
Wet Weather Volume Cost Allocation Alternatives
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Table 3-17
Alternative 2(a)
MSD Wet Weather Cost Allocation & Rates
Distribution of Estimated Wet Weather Flows to Capacity and Volume
Capacity Based on Minimum 8-inchfeet of S t P'
Description
ys
Pipe Size/Length
em ipe
Allocation Factors
Combined
Capacity
Volume
Pipe Size
Various'
8 inch2
Length
7,766,052
7,766,052
Total inch -feet
181,407,190
62,128,416
Sanitary
Pipe Size
Various [1]
8 inch
Length
23,088,498
23,088,498
Total inch -feet
230,209,709
184,707,984
Combined & Sanitary
Total Feet of Pipe
30,854,550
30,854,550
Total inch -feet
411,616,899
246,836,400
60%
40%
From 1 inch through 196-Inch diameter pipe. Total inch -feet equals length of pipeline in system
times respective diameter in inches.
2 Total inch -feet equals length times 8 (inches).
The allocation factors determined in this alternative are 60 percent to
customer/capacity and 40 percent to volume. This is a significant shift from the
existing allocation factors of 37 percent customer/capacity and 40 percent volume.
These results indicate that a major portion of MSD's collection system is dedicated to
conveying both wastewater and wet weather flows at a minimum level of service.
This minimum level of service is common to all customers.
Alternative 2 (a) - Existing Rates
Table 3-18 provides a comparison of revenues derived from existing rates versus
estimated revenues derived using the allocation factors determined for this
alternative. Table 3-18 also presents the revenues required per customer class with
stormwater costs excluded. In order to present the wastewater system costs
separately, the column "Revision Without Stormwater Costs1l does not include
$13,657,602 in stormwater system costs.
oeM
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Section 3
Wet Weather Volume Cost Allocation Alternatives
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Table 3-22
Alternative 2(c)
MSD Wet Weather Cost Allocation & Rates
Wet Weather Volume & Unfunded Stormwater Costs Distributed by Impervious Area
8-Inch-Foot Pipe Allocation Comparative Revenue
Factors Utilized
,
Ill Allocation
33%
Capacity
60%
Volume
40%
Revenue Comparison
Existing
Cost Of
Service
Revision
Percent
Change
Revision
Without
Stormwater
Costs
Percent
Change
Metered Customers
Single Family
$72,704,600
$60,018,746
-17.4%
$60,018,746
-17.4%
Multifamily
19,269,000
14,393,756
-25.3%
14,393,756
-25.3%
Non -Residential:
Anheuser-Busch
7,566,700
5,978,328
-21.0
5,978,328
-21.0%
All Other
59,601,100
44,614,953
-25.2%
44,614,953
-25.2%
Total
$159,141,400
$125,005,783
$125,005,783
UnMetered Customers
Single Family
$16,871,000
$13,672,418
-19.0%
$13,672,418
-19.0%
Multi Family
10,327,500
8,023,582
-22.3%
8,023,582
-22.3%
Total
$27,198,500
$21,696,000
$21,696,000
Impervious Area Charges
Single Family
$17,613,726
$11,545,035
Multifamily
3,488,402
2,286,497
Non -Residential:
Anheuser-Busch
85,210
55,901
All Other
18,450,778
12,093,082
Total
$39,638,116
$25,980,516
Total System
Single Family
$89,575,600
$91,304,890
1.9%
$85,236,200
-4.8%
Multifamily
29,596,500
25,905,740
-12.5%
24,703,835
-16.5%
Non -Residential
59,601,100
63,065,731
+5.8%
56,708,035
-20.3%
Anheuser-Busch
7,566,700
6,063,538
-19.9%
6,034,225
-4.8%
Total System
$186,339,900
$186,339,899
$172,682,295
The multi family customer class appears to realize a significant decrease in rates
compared to the other two classes of customers that would experience a slight
increase with this alternative.
Table 3-23 presents the rates using this alternative and modified rate design to
include impervious area rates to recover wet weather volume and subsidized
stormwater related charges.
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Table-3-23
Alternative 2(c)
MSD Wet Weather Cost Allocation & Rates
Wet Weather Volume & Unfunded Stormwater Costs Distributed by Impervious Area, Impervious
Area Rate Comparison Comparative Rates
Factors Utilized
I/I Allocation
33%
Capacity
60%
Volume
40%
Rate Comparison.
Existing Cost Of Service
Revision
Percent
Change
Revision
without
Stormwater
Costs
Percent
Change
Billing and Collection Charge/Bill
$1.14
$1.14 0%
$1.14
0%
System Availability Charge/Bill
$6.50
$7.60 18%
$7.60
18%
Compliance Charge/Bill
$11.35
$11.35 0%
$11.35
0%
Volume Charge $/Ccf
$1.66
$1.10 -34%
$1.10
-34%
Impervious Area Charge $/Sq.Ft.
$0.0159
$0.0104
Typical Residential Bill - 8 Ccf/Month
$20.92
$17.54
-16%
$17.54
-16%
Typical Residential Impervious Area Fee
$3.30
$2.16
3.5.3 Alternative 3 - Capacity allocation based on 50-fool/6-inch
Lateral
This alternative is similar to the previous alternative except it allocates wet weather
costs assuming that all customer connections have a minimum equivalent of a six inch
diameter, 50-foot lateral. The number of inch -feet connections are totaled and added
to the calculated inch -foot collection system determined in Alternative 1. The total of
the inch -feet of laterals is divided by the inch -feet of collection system plus laterals.
The quotient is the allocation factor for customer/capacity.
Table 3-24 provides the calculation of the wet weather allocation factors with this
alternative.
`'M
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Table 3-24
Alternative 3
MSD Wet Weather Cost Allocation & Rates
Distribution of Estimated Wet Weather Flows to Capacity and Volume
Capacity Based on 50-Feet of 6-Inch Diameter Laterals
Description
Allocation
Total Bills
5,159,292
Months
12
# Connections
429,941
Average Lateral inch-ft.1
300
Total Lateral inch-ft.2
128,982,300
24%
Capacity
Volume
Total System inch-ft.3
411,616,899
76%
System & Lateral
540,599,199
1 Average lateral inch -feet equals 50-foot length times (6-inch diameter).
2 Total lateral inch -feet equals 300 times number of connection.
3 Total system inch -feet length from Table 3-16.
This alternative distributes the wet weather costs with an estimated 24 percent to
customer/ capacity and 76 percent to volume. This allocates more costs onto the
volume component of the existing rate design.
Alternative 3(a) Existing Rates
Table 3-25 provides the revenues derived from existing rates compared to estimated
revenues determined using the allocation factors for this alternative. Table 3-25 also
presents the revenues required per customer class with stormwater costs excluded. In
order to present the wastewater system costs separately, the column "Revision
Without Stormwater Costs" does not include $13,657,602 in stormwater system costs.
1
1 CDM
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Table 3-25
Alternative 3(a)
MSD Wet Weather Cost Allocation & Rates
Distribution of Estimated Wet Weather Flows to Capacity and Volume
Capacity Based on 50-Feet of 6-Inch Diameter laterals Comparative Revei
Factors Utilized
-
III Allocation
33%
Capacity
24%
Volume
76%
Revenue Comparison
Existing
Cost Of
Service
Revision
Percent
Change
Revision
Without
Stormwater
Costs
Percent
Change
Metered Customers
Single Family
$72,704,600
$66,760,514
-8.2%
$61,586,748
-15.3%
Multifamily
19,269,000
20,465,206
6.2%
18,875,961
-2%
Non -Residential:
Anheuser-Busch
7,566,700
8,231,305
8.8%
7,827,802
3.5%
All Other
59,601,100
64,522,006
8.2%
60,075,440
0.8%
Total
$159,141,400
$159,979,031
$148,365,951
UnMetered Customers
Single Family
$16,871,000
$15,958,377
-5.4%
$14,721,098
-12.7%
Multi Family
10,327,500
10,402,492
0.7%
9,595,250
-7.1%
Total
$27,198,500
$26,360,868
$24,316,348
Impervious Area Charges
Single Family
Multifamily
Non -Residential:
Anheuser-Busch
All Other
•
Total
Total System
Single Family
$89,575,600
$82,718,890
-7.6%
$76,307,846
-14.8%
Multifamily
29,596,500
30,867,697
4.3%
28,471,211
-3.8%
Non -Residential
59,601,100
64,522,006
8.2%
60,075,440
8%
Anheuser-Busch
7,566,700
8,230,305
8.8%
7,827,802
3.5%
Total System
$186,339,900
$186,339,899
$172,682,299
This alternative increases the cost of service to large billable volume customers.
Conversely, it decreases the cost to the smaller customers. Multi family customers
will have an increase, albeit small, in their bills.
Table 3-26 presents the rate changes affected by this alternative.
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Table 3-26
Alternative 3(a)
MSD Wet Weather Cost Allocation & Rates
Distribution of Estimated Wet Weather Flows to Capacity and Volume
Capacity Based on 50-Feet of 6-Inch Diameter Laterals Comparative Rat
Factors Utilized
vV
I/I Allocation
33%
Capacity
24%
Volume
76%
Rate Comparison
Existing Cost Of Service
Revision
Percent
Change
Revision
without
Stormwater
Costs
Percent
Change
Billing and Collection Charge/Bill
$1.14
$1.14
0%
$1.14
0%
System Availability Charge/Bill
$6.50
$3.39
-47.8%
$3.04
-53.2%
Compliance Charge/Bill
$11.35
$11.35
0%
$11.35
0%
Volume Charge $/Ccf
$1.66
$1.83
10%
$1.69
1.8%
Impervious Area Charge $/Sq.Ft.
11 $0.0000
$0.0000
Typical Residential Bill - 8 Ccf/Month
$20.92
$19.17
-8.4%
$17.70
-15.4%
Typical Residential Impervious Area Fee
$0.00
$0.00
Alternative 3(a) indicates an eight percent decrease in typical residential bills. Again,
the customers with large contributed volume will have a considerable increase. There
are some intra-class inequities for the residential customers using this alternative;
multi -family customers with a slight increase in the cost of wet weather and single
family residents a decrease. In addition, large commercial and industrial customers
will see larger increases in wet weather costs compared to those commercial
customers with smaller billable volumes.
Alternative 3(b) - Wet Weather Volume Costs Recovered Using Impervious Area
Charge
Table 3-27 displays the revenue from existing rates compared to revenue derived
from rates with wet weather volume charges passed onto customers based on
impervious area. Table 3-27 also presents the revenues required per customer class
with stormwater costs excluded. In order to present the wastewater system costs
separately, the column "Revision Without Stormwater Costs" does not include
$13,657,602 in stormwater system costs.
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Table 3-27
Alternative 3(b)
Capacity Based on 50-Feet of 6-Inch Width Laterals Comparative Wet Weather Capacity Allocated
by Customer - Volume by Impervious Area Revenue Comparison
Factors Utilized
I/1 Allocation
33%
Capacity
24%
Volume
76%
Revenue Comparison
Existing
Cost Of
Service
Revision
Percent
Change
Revision
Without
Stormwater
Costs
Percent
Change
Metered Customers
Single Family
$72,704,600
$45,297,391
-37.7%
$42,326,707
-41.8%
Multifamily
19,269,000
14,776,805
-23.3%
13,771,446
-28.5%
Non -Residential:
Anheuser-Busch
7,566,700
5,997,540
-20.8%
5,823,322
-23%
All Other
59,601,100
46,927,167
-21.3%
44,286,622
-25.7%
Total
$159,141,400
$112,998,903
$106,208,097
UnMetered Customers
Single Family
$16,871,000
$10,977,889
-35.0%
$10,251,833
-39.2%
Multi Family
10,327,500
7,353,711
-28.8%
6,859,411
-33.6%
Total
$27,198,500
$18,331,600
$17,111,244
Impervious Area Charges
Single Family
$24,444,682
$21,935,558
Multifamily
4,841,275
4,344,342
Non -Residential:
Anheuser-Busch
118,251
106,119
All Other
25,605,189
22,976,939
Total
$55,009,397
$49,362,958
Total System
Single Family
$89,575,600
$80,719,961
-9.9%
$74,514,097
-16.8%
Multifamily
29,596,500
26,971,790
-8.9%
24,975,199
-15.6%
Non -Residential
59,601,100
72,532,356
21.7%
67,263,561
12.9%
Anheuser-Busch
7,566,700
6,115,791
-19.3%
5,929,441
-21.6%
Total System
$186,339,900
$186,339,898
$172,682,298
Table 3-28 presents the rates using this alternative and modified rate design to
include impervious area rates to recover wet weather volume related charges.
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Table 3-28
Alternative 3(b)
Capacity Based on 50-Feet of 6-Inch Width Laterals Comparative Wet Weather Capacity Allocated
by Customer -Volume by Impervious Area Com arative Rat
Factors Utilized
p
es
Ill Allocation
33%
Capacity
24%
Volume
76%
Rate Comparison
Existing Cost Of Service
Revision
Percent
Change
Revision
without
Stormwater
Costs
Percent
Change
Billing and Collection Charge/Bill
$1.14
$1.14
0%
$1.14
0%
System Availability Charge/Bill
$6.50
$3.39
-47.8%
$3.04
-53.2%
Compliance Charge/Bill
$11.35
$11.35
0%
$11.35
0%
Volume Charge $/Ccf
$1.66
$1.17
-30%
$1.10
-33.7%
Impervious Area Charge $/Sq.Ft.
1 $0.0220
$0.0197
Typical Residential Bill - 8 Ccf/Month
$20.92
$13.89
-33.6%
$12.98
-38%
Typical Residential Impervious Area Fee
$4.59
$4.11
The net affect of this alternative on a typical single family residential bill is
approximately a 12 percent decrease (wastewater plus impervious area charge
compared to existing bill). Non-residential customers will realize a significant
increase.
Alternative 3(c) - Wet Weather Volume and Unfunded Stormwater Costs -
Impervious Area
Table 3-29 displays the revenue from existing rates compared to revenue derived
from rates with wet weather volume and subsidized stormwater costs included in the
wastewater rate passed onto customers based on impervious area. Table 3-29 also
presents the revenues required per customer class with stormwater costs excluded. In
order to present the wastewater system costs separately, the column "Revision
Without Stormwater Costs" does not include $13,657,602 in stormwater system costs.
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Table 3-29
Alternative 3(c)
MSD Wet Weather Cost Allocation & Rates
Wet Weather Volume & Unfunded Stormwater Costs Distributed by Impervious Area
8-Inch-Foot Pipe Allocation Comparative Revenue
Factors Utilized
I/I Allocation
33%
Capacity
Volume
24%
76%
Revenue Comparison
Existing
Cost Of
Service
Metered Customers
Revision
Percent
Change
Revision
Without
Stormwater
Costs
Percent
Change
Single Family
Multifamily
Non -Residential:
$72,704,600
19,269,000
$42,326,707
13, 771,446
-41.8%
-28.5%
$42,326,707
13,771,446
-41.8%
-28.5%
Anheuser-Busch
7,566,700
5,823,322
-23.0%
All Other
59,601,100
44,286,622
-25.7%
Total
$159,141,400
$106,208,097
UnMetered Customers
5,823,322
44,286,622
$106,208,097
-23.0%
-25.7%
Single Family
Multi Family
Total
$16,871,000
10,327,500
$27,198,500
$10,251,833
6,859,411
$17,111,244
-39.2%
-33.6%
Impervious Area Charges
Single Family
Multifamily
Non -Residential:
$28,004,413
5,546,280
$10,251,833
6,859,411
$17,111,244
$21,935,558
4,344,342
-39.2%
-33.6%
Anheuser-Busch
135,479
All Other
29,334,386
Total
$63,020,558
Total System
Single Family
Multifamily
Non -Residential
$89,575,600
29,596,500
59,601,100
$80,582,953
26,177,137
73,621,008
-10.0%
-11.6%
23.5%
106,119
22,976,939
$49,362,958
$74,514,097
Anheuser-Busch
7,566,700
5,958,801
-21.2%
24,975,199
67,263,561
Total System
$186,339,900
$186,339,899
5,929,441
-16.8%
-15.6%
$172,682,298
12.9%
-21.6%
This alternative creates a significant increase for the non-residential class of customer
while providing a rate decrease of over 10 percent for residential and multi family
class customers. There is a significant shift in the revenue requirement recovered
from the non-residential class compared to residential and multi family, producing
some perceived inter -class inequity.
CDMI
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Table 3-30 presents the rates using this alternative and modified rate design to
include impervious area rates to recover wet weather volume and subsidized
stormwater related charges.
Table 3-30
Alternative 3(c)
MSD Wet Weather Cost Allocation & Rates
Wet Weather Volume & Unfunded Stormwater Costs Distributed by Impervious Area
Impervious Area Rate Comparison
Factors Utilized
Ill Allocation
33%
Capacity
24%
Volume
76%
Rate Comparison
Existing Cost Of Service
Revision
Percent
Change
Revision
without
Stormwater
Costs
Percent
Change
Billing and Collection Charge/Bill
$1.14
$1.14
0%
$1.14
0%
System Availability Charge/Bill
$6.50
$3.04
-53.2%
$3.04
-53.2%
Compliance Charge/Bill
$11.35
$11.35
0%
$11.35
0%
Volume Charge $lCcf
$1.66
$1.10
-34%
$1.10
-33.7%
Impervious Area Charge $/S•.Ft.
$0.0252
$0.0197
Typical Residential Bill - 8 Ccf/Month
$20.92
$12.98
-38%
$12.98
-38%
Typical Residential Impervious Area Fee
$5.25
$4.11
3.6 Conclusion
The first alternative group was designed to develop the range of changes in rates from
different wet weather cost allocation factors, i.e., the second primary factor used by
the MSD rate model to determine wet weather costs allocated to capacity or volume
functions (37/63 ratio). It clearly demonstrated that changing the existing allocation
factor from the existing 37/63 to 100 percent volume and 0 percent capacity would
increase the large volume/non-residential customer rates about 17 percent and
decrease residential rates by about 16 percent. On the other hand, changing the
existing allocation factor to 0 percent volume and 100 percent capacity will create a
29 percent decrease in non-residential rates and a 27 percent increase in residential
rates. This defines the range of rate change that can be expected from changing the
wet weather cost allocation factor.
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In addition to evaluating supportable changes in the primary wet weather allocation
factors included in the rate model, CDM included several alternatives designed to
investigate rate structure enhancements. These alternatives were intended to offer
increased equity relating to wet weather and stormwater costs. Specifically, the
alternatives include adding an impervious area charge rate component to the current
wastewater rate structure.
These along with other relevant alternatives will be ranked in Section 4 of this study
using four criteria. The alternatives ranked will be Alternatives 1 through 3,
including the Existing Rate Model (A) and subsets identified in each alternative.
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Section 4
Allocation Alternative Comparison
4.1 Introduction
Tables 4-1 and 4-2 present impacts to the rate categories and to customer classes for
the various alternatives.
Matrix Conclusions and Preferred Alternative Identification
The alternatives described in Section 3 were screened using a decision matrix.
To evaluate and rank the alternatives, four basic criteria were identified and defined.
These criteria included:
• Rate Impact;
• Class Equity which included both Inter -Class Equity and Intra-Class Equity;
• Ratemaking Methodology; and
• Administrative Simplicity.
Each of the four ranking criteria have been developed taking into consideration the
criteria put forth to govern rates in the MSD Rate Commission Charter. The Rate
Commission Criteria states that any proposed rate adjustment recommended by the
Rate Commission for approval by the MSD Board will:
1. Be consistent with constitutional, statutory or common law as amended from
time to time;
2. Enhance the District's ability to provide adequate sewer and drainage systems
and facilities, or related services;
3. Be consistent with and not in violation of any covenant or provision relating to
any outstanding bonds or indebtedness of the District;
4. Not impair the ability of the District to comply with applicable Federal or State
laws or regulations as amended from time to time; and
5. Impose a fair and reasonable burden on all classes of rate payers.
The criteria pertinent to legal and regulatory compliance was not included in the
evaluation as all of the alternatives meet this standard. There are issues relative to the
ability to legally challenge the alternatives; however, this issue is best addressed in a
legal forum.
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Section 4
Allocation Alternative Comparison
✓4.2 Evaluation Criteria and Ranking Methodology
The four criteria used to rank the alternatives identified in this study are designed to
address the Rate Commission Charter mandates. A description of the evaluation
factors used to rank the alternatives and the method for assigning point values to each
criterion is presented in the following sections.
4.2.1 Rate Impact
The Rate Impact of the Wet Weather Cost Allocation alternatives has been evaluated
based on the change in monthly cost to single family customers. The mean value
(increase or decrease) in monthly cost for single family customer was determined by
calculating the change in monthly revenue allocation to the single family customer
class, divided by the number of single family customers. Rate Impact is one of two
factors used to evaluate whether the proposed alternatives adequately address criteria
number 5 of the Rate Commission, "Impose a fair and reasonable burden on all classes of
rate payer."
The standard deviation for the single family monthly costs (increase or decrease from
existing costs) was calculated against zero (0). A numeric ranking from 10 (the
alternative with the lowest standard deviation) to 1 (for the alternative for the largest
standard deviation) was assigned to each alternative in descending order. Options
that have the same standard deviation were give the same ranking and the next
lowest ranked alternative given the next lower number. The standard deviation for
each alternative and its ranking are shown in Table 4-1.
Table 4-1
XRate Impact
Changes to Single Family Bill
Standard Deviation and Evaluation
Alternative
Existing
1a
lb
1c
2a
2b
_
2c
3a
3b
3c
Bill Variance
$(s)
0
-0.61
-0.31
-0.31
0.86
1.05
1.05
-1.44
-1.08
-1.08
Standard
Deviation
0
0.431
0.219
0.219
0.608
0.742
0.742
1.018
0.764
0.764
Score
10
8
9
9
7
6
6
4
5
5
Rate Impact Criteria Weighting
Rate Impact is one measurement of cost distribution and how the rate alternatives
would impact specific category of rate payers. The criteria pertinent to Rate Impact
has been given a 20 percent weight in the evaluation matrix.
4-2
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P:120314 MS0143488 1.1 Cost Allocation StudysFinal ReponlSection4fina1.0oc
Section 4
Allocation Alternative Comparison
4.2.2 Ratemaking Methodology
The Ratemaking criteria is used to quantify how supportable the information is that
was used for establishing and defining capacity, volume and wet weather volume
functions in MSD's rate model and distributing volume costs to the customer classes.
This factor is also used to quantify the relative accuracy of the information based on
rate setting standards that recommend costs be allocated in terms of cost causing
factors, with the factors used being of a quantifiable nature. For example, the total
length of laterals was based on assumed length of each lateral and it was assumed
each account had one lateral. This information was not field verified or tested as part
of this study and would be given a lower score. In contrast, the total system length of
8-inch pipe was based on MSD asset inventory and on MSD system maps. While no
field verification was conducted as part of this study, the inventory is based on
system information, which increases its reliability. Accordingly, the options that use
8-inch pipe, feet as a basis for determining capacity and volume function would score
higher. Ratemaking methodology relates to criteria number 2 of the Rate Commission, "a rate
adjustment should enhance the District's ability to provide adequate sewer and drainage
systems and facilities or related services."
Each alternative was given a score of 10 and 2 points were deducted for each of these
factors:
• Stormwater cost distributed by billed volume;
• Use of current 45/55 percent, Wet weather/Wastewater factor;
• Wet weather volume costs distributed based on billed volume;
• Use of current 33/67 percent, distribution of capacity/volume costs;
• Use of laterals length assumptions as basis of capacity/volume costs.
Ratemaking Methodology Weighting Factor
Ratemaking Methodology was used to quantify how supportable the information is
that was used for establishing and defining capacity, volume and wet weather
volume functions in MSD's rate model and distributing volume costs to the customer
classes Ratemaking Methodology criteria has been given a 40 percent weight in the
evaluation matrix criterion.
4.2.3 Class Equity
Inter -Class Equity
This is designed to address the Rate Commission Charter mandate Number 5 - any
proposed rate adjustment will impose a fair and reasonable burden on all classes of ratepayers.
When evaluating rate structures one of the fundamental requirements is the equitable
distribution of utility costs to all customers based on customer's demand
characteristics. Equitable rate structures attempt to eliminate or at least limit cross
4-3
PA20314 MS0143486 I -I Cost Allocation StudyiFinaI Report\Section4final.0oc
Section 4
Allocation Alternative Comparison
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subsidization (or the appearance of such) between customer classes. This is called
vertical equity, e.g. industrial customers are not subsidizing rates for residential
customers or vice versa.
The measurement used to rank the alternatives in the inter -class equity criteria was
based on the mean value (increase or decrease in rates) for each customer class and
then the standard deviation was calculated for the composite of customer class mean
values for each alternative. The mean (increase or decrease) in monthly cost for each
customer class was determined by calculating the change in monthly revenue
allocation to that customer class, divided by the number of customers in that class.
The standard deviation is an objective measure for ranking alternatives under the
inter -class equity criteria and judges the overall impact the change in rates have on
any one customer class compared to others. As an example, if a rate adjustment is
proposed that shifts the revenue requirement recovery from residential to non-
residential customers by 10 percent or more this would be considered inequitable
(compared to alternatives with less of a shift in revenues) and score low in ranking.
This low score would be given even though there may be clear justification for the
change in cost allocation. This is because the shift would create a "rate shock" in the
non-residential class of customer and perhaps send the wrong price signals to the
residential customers.
A numeric ranking from 10 (being the alternative with the lowest standard deviation)
to 1 (for the alternative for the highest standard deviation) was assigned to each
alternative in descending order. Options that have the same standard deviation were
give the same ranking and the next lowest ranked alternative given the next lower
number. The standard deviation for each alternative and its ranking are shown in
Table 4-2.
Table 4-2
Inter -Class Equity Changes to Customer Class Costs
Standard Deviation and Evaluation Score
Alternative
Existing
la
lb
lc
2a
2b
2c
3a
3b
3c
Single Family
Variance $(s)
0.0
-0.61
-0.31
-0.31
0.86
1.05
1.05
-1.44
-1.08
-1.08
Multi Family
Variance $(s)
0.0
0.83
-6.72
-6.72
-1.48
-6.72
-6.72
2.13
-6.98
-6.98
Non -
Residential
Variance $(s)
0.0
7.1
16.01
16.01
-9.42
-3.76
-3.76
16.44
27.19
27.19
Standard
Deviation
0.0
4.01
11.72
11.72
5.39
3.72
3.72
9.46
18.27
18.27
Score
10
9
5
5
7
8
8
6
4
4
Intra-Class Equity
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Section 4
Allocation Alternative Comparison
The intra-class equity ranking criteria is also designed to address the Rate
Commission Charter mandate Number 5 - any proposed rate adjustment will impose a fair
and reasonable burden on all classes of ratepayers. In many cases evaluating the vertical
equity is not enough to determine the fairness of a rate structure. With larger utilities
that have numerous customers, customers within a class will not always have the
same demand characteristics. This then leads to intra-class subsidization situations.
This is called horizontal equity, i.e., customers within a class are not supporting other
customers in the same customer class.
The principal measure of equity using the intra-class ranking criterion was a review of
the typical billing summary prepared for each alternative. This summary determines
what typical bill ratepayers will be charged based on different levels of service and
compares them to charges using existing (baseline) rates. Multiple levels of billable
volumes and pollutant strengths were used in the summary in Appendix B to capture
the range of impacts between customer classes and within customer classes. The
summary of typical bills is presented in Appendix B. The typical bills are based on
the accounts and information presented to the Stormwater Advisory Committee
meetings conducted in the spring of 2001. Significant increases or decreases within
classes will reduce the ranking in the intra-class equity criteria.
The mean value (increase or decrease in rates) was calculated for each single family _
customer type identified in Appendix B. The standard deviation was then calculated
for the single family customer class as a composite for each alternative.
The same procedure was followed for non-residential customers, however, only the
following customer types were analyzed:
• Tax Exempt Annexed Area - 25 ccf;
• Tax Exempt Annexed Area - 50 ccf; and
• High Rise Commercial -1,000 ccf.
There was no multi -family customer information in Appendix B; therefore the mean
value for the average of multi -family customers was used.
The standard deviation for each customer class was then weighted based on each
customer class's percent of the total annual bills and the weighted standard deviations
summed. The standard deviation for each alternative and its ranking are shown in
Table 4-3.
P:120314 MSD143486 I I Cost Allocation Stnd?Final ReponlSection4final.doc
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Section 4
Allocation Alternative Comparison
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Table 4-3
Intra-Class Equity Changes to Customer Class Billings
Standard Deviation and Evaluation Score
Alternative
Customers
Bills 2005
Estimate
Existing
1a
lb
1c
2a
2b
2c
3a
3b
3c
Single
Family
4,315,770
(83.65%)
0
0.336
0.97
0.97
0.54
1.08
1.08
0.83
1.14
1.14
Multi-
Family
535,550
(10.38%)
0
0.59
4.75
4.75
1.05
4.43
4.43
1.51
4.94
4.94
Non-
Residential
307,972
(5.97)
0
38.06
115.31
115.31
61.35
158.72
158.72
94.26
90.79
90.79
Weighted
Standard
Deviation
0
2.62
8.19
8.19
4.22
10.84
10.84
6.48
6.88
6.88
Score
10
9
5
5
8
4
4
7
6
6
Inter -Class Equity Criteria and Intra-Class Equity Criteria Weighting
Inter -class and Intra-class equity criterion was scored from 1 though 10 (10 being the
most favorable) as described above. The score for the Inter and Intra-class equity was
given the same weight and averaged to determine each alternative ranking. Table 4-4
provides the averaged score for each alternative. This average was used to rank each -
alternative for the Class Equity criteria. The Class Equity criteria have been given a
20 percent weight in the evaluation matrix. CDM reviewed the alternatives using
measures to determine the vertical equity it offers. Each alternative had the
opportunity to be ranked in the inter -class equity criteria.
Table 4-4
Class Eauit
Alternative
Existing
1a
lb
1c
2a
2b -
J 2c
3a
3b
3c
Inter Class
Equity
10
9
5
5
7
8
8
6
4
4
Intra Class
Equity
10
9
5
5
8
4
4
7
6
6
Class Equity
Score
10
9
5
5
7.5
6
6
6.5
5
5
4.2.4 Administrative Simplicity
The administrative simplicity criteria addresses Rate Commission Charter criteria
Number 2 - a rate adjustment should enhance the District's abilihj to provide adequate sewer
and drainage systems and facilities, or related services. One of the factors to consider when
evaluating a rate structure is the utility's ability to implement any change in the
billing process that the alternative rate structure requires. It is also important that a
change in rate structure be easy for the public to understand and accept.
Each alternative was given a score of 10 and 2 points were deducted for each of these
factors:
CDM
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Table 4-5
Existing Rate Structure and Alternative 1, 37/63 Percent CapacityNolume Allocation
Wastewater Allocation Alternative Evaluation Matrix
No.
Alternative Description
Rate Impact (a) (c)
Ratemaking
Methodology
Class
Equity (b) (c)
Administrative
Simplicity
8 - existing rate
structure and billing
process
Weighted = 0.80
Total
Weight
6.60
A
45% Wet Weather Allocation
37/63 CapacityNolume
Allocation
Existing Rate Structure.
10
Weighted = 2.00
2- Wet Weather and
capacity and volume cost
allocations not supported
on engineering/economic
basis
Weighted = 0.80
10
Weighted = 3.00
1(a)
33% Wet Weather Allocation
37/63 CapacityNolume
Allocation
Updated Wet Weather
Flow Percentage
Wet Weather Volume
Cost Allocated Based on
Billed Volume
8
Weighted = 1.6
4- capacity/volume
allocation not support ed
on engineering/economic
basis
Weighted = 1.60
9
Weighted = 2.70
8- existing rate
structure and billing
process
Weighted = 0.80
6.70
1(b)
33% Wet Weather Allocation
37/63 CapacityNolume
Allocation
Updated Wet Weather
Flow Percentage
Wet Weather Volume
Cost Allocated Based on
Impervious Area
9
Weighted = 1.80
6 - increase equity
adding impervious area
charge
Weighted = 2.40
5
Weighted = 1.50
2 - requires
impervious area
billing software
modifications
Weighted = 0.20
5.90
1(c)
33% Wet Weather Allocation
37/63 CapacityNolume
Allocation
Updated Wet Weather
Flow Percentage
Wet Weather Volume and
Subsidized Stormwater
Cost Allocated Based on
Impervious Area
9
Weighted = 1.80
8 - increase equity
adding impervious area
charge for stormwater
costs
Weighted = 3.20
5
Weighted = 1.50
8 - requires
impervious area
billing software
modifications
Weighted = 0.80
7.30
Maximum Score
10
10
10
10
Weighting Factors
20%
40%
30%
10%
(a) Rate Impact is based on the Standard Deviation of the Average Single Family Residentia bill.
(b) Class Equity is based on the Average of (Standard Deviation of an Inter Class calculation plus the Standard Deviation Infra Class calculation
(weighted per percent of bills)).
(c) Rate Impact and Class Equity are based on wastewater revenue for the customer class evaluated.
_& ■ ai soma mod use Dui ..■ramill mid aid NNW wad mat tlllN ball M
Table 4-6
Alternative 2 Minimum 8-Inch-Feet of System Pipe -
Wastewater Allocation Alternative Evaluation Matrix
No.
Alternative Description
Rate Impact (a) (c)
Ratemaking
Methodology
Class
Equity (b) (c)
Administrative
Simplicity
Total
Weight
2(a)
33% Wet Weather
Allocation
60/40 CapacityNolume
Allocation
Updated Wet Weather
Flow Percentage
Wet Weather Volume
Cost Allocated Based on
Billed Volume
7
Weighted = 1.40
4- wet weather flow and
wet weather cost
allocation factors
supportable
Weighted = 1.60
7.5
Weighted = 2.25
8 - existing rate
structure and billing
process
Weighted = 0.80
6.05
2(b)
33% Wet Weather
Allocation
60/40 CapacityNolume
Allocation
Updated Wet Weather
Flow Percentage
Wet Weather Volume
Cost Allocated Based on
Impervious Area
6
Weighted = 1.20
8 - wet weather flow and
wet weather cost
allocation factors
supportable
Weighted = 3.20
6
Weighted = 1.80
2 - requires
impervious area
billing software
modifications
Weighted = 0.20
6.40
2(c)
33% Wet Weather
Allocation
60/40 CapacityNolume
Allocation
Updated Wet Weather
Flow Percentage
Wet Weather Volume and
Subsidized Stormwater
Cost Allocated Based on
Impervious Area
6
Weighted = 1.20
10 - increase equity
adding impervious area
charge for stormwater
costs
Weighted = 400
6
Weighted = 1.80
8 - requires
impervious area
billing software
modifications
Weighted = 0.80
7.80
Maximum Score
10
10
10
10
Weighting Factors
20%
40%
30%
10%
(a) Rate Impact is based on the Standard Deviation of the Average Single Family Residential bill.
(b) Class Equity is based on the Average of (Standard Deviation of an Inter Class calculation plus the Standard Deviation Intra Class calculation (weighted per percent of bills)).
(c) Rate Impact and Class Equity are based on wastewater revenue for the customer classes evaluated.
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Table 4-7
Alternative 2 Minimum 8-Inch-Feet of System Pipe - CapacityNolume Allocation
Wastewater Allocation Alternative Evaluation Matrix
No.
Alternative Description
Rate Impact (a) (c)
Ratemaking
Methodology
Class
Equity (b) (c)
Administrative
Simplicity
Total
Weight
3(a)
33% Wet Weather
Allocation
24/76 CapacityNolume
Allocation
Updated Wet Weather
Flow Percentage
Wet Weather Volume
Cost Allocated Based on
Billed Volume
4
Weighted = 0.80
2 - wet weather flow and
wet weather cost
allocation factors
supportable
Weighted = 0.80
6.5
Weighted = 1.95
6 - existing rate
structure and billing
process
Weighted = 0.60
4.15
3(b)
33% Wet Weather
Allocation
24/76 CapacityNolume
Allocation
Updated Wet Weather
Flow Percentage
Wet Weather Volume
Cost Allocated Based on
Impervious Area
5
Weighted = 1.00
6 - wet weather flow and
wet weather cost
allocation factors
supportable
a charge for stormwater
costs
Weighted = 2.40
5
Weighted = 1.50
2 - requires
impervious area
billing software
modifications
Weighted = 0.20
5.10
3(c)
33% Wet Weather
Allocation
24/76 CapacityNolume
Allocation
Updated Wet Weather
Flow Percentage
Wet Weather Volume and
Subsidized Stormwater
Cost Allocated Based on
Impervious Area
5
Weighted = 1.00
8 - increase equity
adding impervious area
charge for stormwater
costs
Weighted = 3.20
5
Weighted = 1.50
6 - requires
impervious area
billing software
modifications
Weighted = 0.60
6.30
Maximum Score
10
10
10
10
Weighting Factors
20%
40%
30%
10%
(a) Rate Impact is based on the Standard Deviation of the Average Single Family Residential bill.
(b) Class Equity is based on the Average of (Standard Deviation of an Inter Class calculation plus the Standard Deviation Intra Class calculation (weighted per percent of bills)).
(c) Rate Impact and Class Equity are based on wastewater revenue for the customer class evaluated.
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Table 4-8
Summary of We
Alternatives
Rate
Impact
Rate
Methodology
Class
Equity
Admin
Simplicity
Total
Rank
2 (c) weighted
1.20
4.00
1.80
0.80
7.80
1
1 (c) weighted
1.80
3.20
1.50
0.80
7.30
2
1 (a) weighted
1.60
1.60
2.70
0.80
6.70
3
A weighted
2.00
0.80
3.00
0.80
6.60
4
2 (b) weighted
1.20
3.20
1.80
0.20
6.40
5
3 (c) weighted
1.00
3.20
1.50
0.60
6.30
6
2 (a) weighted
1.40
1.60
2.25
0.80
6.05
7
1 (b) weighted
1.80
2.40
1.50
0.20
5.90
8
3 (b) weighted
1.00
2.40
1.50
0.20
5.10
9
3 (a) weighted
0.80
0.80
1.95
0.60
4.15
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A sewershed level analysis was performed to demonstrate the variability of wet weather
flow on a sub -service area level. The analysis was performed using the 2003 flow
monitoring program data. This data was taken from May to September 2003. Five
representative sewersheds were selected based on available data, service area, and
anticipated I/I contribution. Valid data from the flow meter closest to the downstream
end of the sewershed was used in the analysis. In some sewersheds, several meters had
to be analyzed to account for all of the flow. Rainfall data from rain gauges set up in
conjunction with the 2003 flow monitoring program was used in the analysis. The 15-
minute rainfall data from the gauge closest to the flow meter was used. Rainfall and 15-
minute flow monitoring data was entered into the SHAPE program. SHAPE
decomposes the flow between dry weather and wet weather using selected dry weather
hydrographs. The hydrographs used in SHAPE were set by selecting the days when no
rainfall had occurred for at least six days. The results of the SHAPE analysis for each
watershed are included in Table A-1.
Table A-1
Volumetric Comparison for Selected Sewersheds in 2003 Monitoring Period
Dry Versus Wet
Sewershed
Dry
Wet
Fee Fee Creek
91%
9%
Coldwater Creek .
84%
16%
Deer Creek
68%
32%
Kiefer Creek
95%
5%
Mackenzie Creek
80%
20%
The percentages in Table A-1 do not include contributions from SSOs because it would
require an extensive modeling and calibration effort. SSOs that could be captured for
future conveyance and treatment could significantly increase the percentage of wet
weather flow in the Fee Fee Creek, Coldwater Creek, and Deer Creek sewersheds, which
have 20, 42 and 45 bypasses, respectively. The highest percentage of wet weather flow
calculated was in Deer Creek at 32 percent, which is part of the River Des Peres Service
Area. This percentage correlates well with Figure A-1 where it is shown that the River
Des Peres Service Area had the highest percentage of wet weather flow (not including
CSO contribution) at 23 percent. Mackenzie Creek, also part of the River Des Peres
Service Area had the next highest wet weather flow percentage at 20 percent. Of the
separate areas, Coldwater Creek sewershed, which is part of the Coldwater Creek
Service Area, had the highest percent wet weather flow at 16 percent which also
corresponds to its highest separate service area wet weather flow percentage at 17
percent (Figure A-1). However, Kiefer Creek sewershed, which is part of the Lower
Meramec Service Area, had the lowest wet weather flow percentage at 5 percent.
Because the Kiefer Creek sewershed is a newer system with no SSOs, 5 percent is a
reasonable estimate of wet weather flow percentage, but is not representative of the
A-1
entire Lower Meramec Service Area which had a wet weather flow percentage of 14
percent (Figure A-1).
Figure A-1
Dry Weather Flow vs. Wet Weather Flow Percentage by
Service Area
100%
90%
80%
70%
60%
50%
40%
30%
20%
10%
0%
*Does not include October 2001 flow data
Rainfall volume was compared for each sewershed with the 54-year mean monthly
rainfall totals from the Lambert - St. Louis International rain gauge. The results are
shown in Figure A-2. The rainfall totals show that in all sewersheds, June 2003 was a
wet month compared to the historical mean. The entire flow monitoring period was also
wetter than normal compared to the historical mean. The varying rainfall totals at each
sewershed also demonstrate the localization of rainfall within the system.
A-2
Figure A-2
Monthly Rainfall Totals in Selected Sewersheds Compared to
54-year Mean Monthly Rainfall Total at Lambert -St. Louis International Rain Gauge
25
20
15
= 10
Deer Creek
TO 5 .rre o
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0 2003 ■ Lambert Airport
Mackenzie Creek
25
20
R• 15
Its 5 -AM FAN
,De` 5Ji
QJ ms
0 2003 ■ Lambert Airport
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Wet weather events were also analyzed for each sewershed. Rainfall data was analyzed
using SHAPE which generated event statistics. Five events were analyzed for each
sewershed. The results are shown in Table A-2. Coldwater Creek, and Deer Creek had
the highest percentage of wet weather flow that passed through their respective flow
meter during each event (excluding the <2-month event), ranging from 17 to 46 percent,
and 34 to 56 percent, respectively. Excluding an unusual 25-year event (and the
<2-month event), Kiefer Creek had the lowest wet weather flow passing through the
meter, ranging from 11 to 14 percent.
Rainfall
Volume
(in)
Table A-2
Analysis of Wet Weather Events for Selected Subsewersheds
Rainfall
Duration
(hr)
Peak
Hourly
Intensity
(inthr)
Antecedent
Dry Period
(days)
Fee Fee Creek
Return
Period
% of Wet Weather
Flow Passed
Through the Flow
Meter during the Wet
Weather Event
1.22
13.5
0.55
1.8
2-month
17%
1.19
6
0.47
2.8
3-month
23%
3.2
3.82
30
13.5
1.02
1.82
0.4
6.4
0.44
8.75
0.17
15.6
1-year
5-year
<2-month
33%
21%
6%
Coldwater Creek
1.96
12.25
1.52
0.3
6-month
46%
1.21
8.5
0.76
0.8
2-month
44%
3.05
1.03
13
5
1.15
0.64
6.4
9.5
2-year
2-month
41%
17%
0.7
5.75
0.69
1.2
<2-month
0.3%
1.54
13.25
0.94
0.4
3-month
56%
3.1
12
1.82
6.4
2-year
47%
1.21
6.5
0.74
7.4
2-month
34%
1.83
8.5
1.28
8.1
6-month
38%
0.11
0.75
0.11
1.6
< 2-month
26%
Kiefer Creek
0.79
11.5
0.22
3.1
< 2-month
5%
1.38
13.25
0.82
0.4
2-month
14%
2.53
12.5
1.31
6.4
1.9
9.25
0.86
4.0
1-year
9-month
11%
11%
6.21
39.25
1.6
0.4
Mackenzie Creek
25-year
36%
1.54
13.25
0.94
0.4
3-month
49%
3.1
1.21
12
6.5
1.82
0.74
6.4
7.4
2-year
2-month
40%
21%
0.74
18.75
0.27
1.1
<2-month
46%
3.59
13.5
1.9
0.3
2-year
47%
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Due to differing intensity, antecedent dry period, duration and rainfall volume of wet
weather events, the system response is variable. An example of the variability for each
sewershed is shown in Figure A-3. Longer antecedent dry periods seem to have lower
percentages of wet weather flow, however rainfall volume and peak intensity also
influence the percentage of wet weather flow and the system's response.
Figure A-3
Wet Weather Event Analysis for Percentage of Observed
Wet Weather Flow vs. Antecedent Dry Period
3▪ 40%
o a 30%
m r 20%
c, 3 10%
a 0%
Fee Fee Creek
■
■
5 10 15 20
Antecedent Dry Period (days)
50%
13o
40%
O . 30%
c W
t 20%
2 c
1096
- 0%
Coldwater Creek
2 4 6 8 10
Antecedent Dry Period (days)
Kiefer Creek
■
■
■
2 4 6 8
Antecedent Dry Period (days)
• 60%
• 350%
•o LL 40%
t 30%
2 20%
10%
a- 0%
Deer Creek
■ .
■
2 4 6 8 10
Antecedent Dry Period (days)
60% -
50%
40%
30%
20%
10%
0%
Mackenzie Creek
r ■
2 4 6 8
Antecedent Dry Period (days)
t
A-5
A.2 Data Analysis Limitations
Within each service area, wet weather varies for each sewershed. Extensive analyses are
required to further define the wet weather variability within each sewershed and is
recommended before sewershed corrective actions are initiated. Other limitations
include:
• SSOs have not been modeled or estimated. SSO contribution could be significant in
certain areas with many bypasses. MSD's sewer models could be used to simulate
annual SSO volumes. This task could be undertaken to further refine the wet -
weather volumes.
• The analyses did not include 2004 flow monitoring data. Additional analyses could
be performed once 2004 data is available.
A.3 Conclusions
These analyses demonstrate that wet weather contribution is especially variable between
sewersheds. Wet weather response is increasingly variable between rainfall events
depending on conditions such as antecedent dry period, peak intensity and rainfall
volume. It is important to consider this when evaluating wet weather flow for sewer
rates. A detailed flow monitoring data analysis and modeling program for wet weather
conditions would be necessary to get an accurate account of wet weather flows and
SSOs from separate service areas.
A-6
sad and sod mid imi mud mid mad a gird W mid lili mill end — rrr num am
Alternative 1(a)
Wet Weather Flow Percentage
Factors Utilized:
Ill Allocation
Capacity
Volume
Customer Description
City Residence
City Residence
City Church
Original District Residence
Original District Residence
Original District Residence
Annexed Area Residence
Annexed Area Residence
Tax Exempt - Annexed Area
Tax Exempt - Annexed Area
High Rise Commercial
High Rise Commercial
High Rise Commercial
Crestwood Mall - Commercial
Chesterfield Mall - Commercial
Industrial
Alternative 1(a)
33%
37%
63%
Imprevious
Area
1,833
1,833
21,636
2,790
2,790
2,790
5,412
5,412
19,442
19,442
170,557
170,557
170,557
1,663,820
2,561,271
310,567
Typical Billing Summary
Monthly Bill CCF
$ 0
$ 2
$ 4
$ 6
$ 8
$ 10
$ 12
$ 14
$ - 25
$ 50
$ 1000
$ 10,000
$ 100,000
$ 10,000
$ 50,000
$ 100,000
Monthly Bill
$ 6.07
$ 9.50
$ 12.94
$ 16.37
$ 19.80
$ 23.24
$ 26.67
$ 30.10
$ 48.99
$ 91.90
$ 1,722.70
$ 17,172.33
$ 171,668.65
$ 17,183.68
$ 85,848.71
$ 171,680.00
Combined Bill Existinct Bill Variance
$ 6.07 $ 7.30 -16.84%
$ 9.50 $ 10.62-10.51%
$ 12.94 $ 13.94 -7.19%
$ 16.37 $ 17.26 -5.15%
$ 19.80 $ 20.58 -3.77%
$ 23.24 $ 23.90 -2.77%
$ 26.67 $ 27.22 -2.02%
$ 30.10 $ 30.54 -1.43%
$ 48.99 $ 48.80 0.38%
$ 91.90 $ 90.30 1.77%
$ 1,722.70 $ 1,667.30 3.32%
$ 17,172.33 $ 16,607.30 3.40%
$ 171,668.65 $ 166,007.30 3.41%
$ 17,183.68 $ 16,618.65 3.40%
$ 85,848.71 $ 83,018.65 3.41%
$ 171,680.00 $ 166,018.65 3.41%
sod and mill mil aid OW NW Ili awl and E MIMI fib NW - - it i♦
Alternative 1(b)
Wet Weather Flow Percentage
Factors Utilized:
Ill Allocation
Capacity
Volume
Customer Description
City Residence
City Residence
City Church
Original District Residence
Original District Residence
Original District Residence
Annexed Area Residence
Annexed Area Residence
Tax Exempt - Annexed Area
Tax Exempt - Annexed Area
High Rise Commercial
High Rise Commercial
High Rise Commercial
Crestwood Mail - Commercial
Chesterfield Mall - Commercial
Industrial
Alternative 1(b)
33%
37%
63%
Imprevious
Area
1,833
1,833
21,636
2,790
2,790
2,790
5,412
5,412
19,442
19,442
170,557
170,557
170,557
1,663,820
2,561,271
310,567
Typical Billing Summary
Monthly Bill CCF Monthly Bill Combined Bill Existing Bill Variance
$ 2.79 0 $ 6.07 $ 8.86 $ 7.30 21.36%
$ 2.79 2 $ 8.41 $ 11.20 $ 10.62 5.46%
$ 32.91 4 $ 10.75 $ 43.66 $ 13.94 213.23%
$ 4.24 6 $ 13.09 $ 17.34 $ 17.26 0.44%
$ 4.24 8 $ 15.43 $ 19.68 $ 20.58 -4.39%
$ 4.24 10 $ 17.77 $ 22.02 $ 23.90 -7.88%
$ 8.23 12 $ 20.11 $ 28.35 $ 27.22 4.14%
$ 8.23 14 $ 22.45 $ 30.69 $ 30.54 0.48%
$ 29.57 25 $ 35.33 $ 64.90 $ 48.80 32.99%
$ 29.57 50 $ 64.58 $ 94.16 $ 90.30 4.27%
$ 259.44 1000 $ 1,176.29 $ 1,435.73 $ 1,667.30 -13.89%
$ 259.44 10,000 $ 11,708.22 $ 11,967.66 $ 16,607.30 -27.94%
$ 259.44 100,000 $ 117,027.55 $ 117,286.99 $ 166,007.30-29.35%
$ 2,530.93 10,000 $ 11,719.57 $ 14,250.51 $ 16,618.65 -14.25%
$ 3,896.10 50,000 $ 58,528.16 $ 62,424.26 $ 83,018.65 -24.81%
$ 472.42 100,000 $ 117,038.90 $ 117,511.32 $ 166,018.65 -29.22%
..�i saimi and mod soma mad alma eori smal eriNNW SSW NNW le./ ome inn WM
Alternative 1(c)
Wet Weather Flow Percentage
Factors Utilized:
Ill Allocation
Capacity
Volume
Customer Description
City Residence
City Residence
City Church
Original District Residence
Original District Residence
Original District Residence
Annexed Area Residence
Annexed Area Residence
Tax Exempt - Annexed Area
Tax Exempt - Annexed Area
High Rise Commercial
High Rise Commercial
High Rise Commercial
Crestwood Mall - Commercial
Chesterfield Mall - Commercial
Industrial
Alternative 1(c)
33%
37%
63%
Imprevious
Area
1,833
1,833
21,636
2,790
2,790
2,790
5,412
5,412
19,442
19,442
170,557
170,557
170,557
1,663,820
2,561,271
310,567
Typical Billing Summary
Monthly Bill
$ 3.34
$ 3.34
$ 39.38
$ 5.08
$ 5.08
$ 5.08
$ 9.85
$ 9.85
$ 35.39
$ 35.39
$ 310.45
$ 310.45
$ 310.45
$ 3,028.53
$ 4,662.10
$ 565.30
CCF Monthly Bill
0 $ 5.54
2 $ 7.73
4 $ 9.92
6 $ 12.11
8 $ 14.30
10 $ 16.49
12 $ 18.68
14 $ 20.88
25 $ 32.93
50 $ 60.32
1000 $ 1,101.26
10,000 $ 10,962.78
100,000 $ 109,578.02
10,000 $ 10,974.14
50,000 $ 54,803.13
100,000 $ 109,589.37
Combined Bill Existing Bill Variance
$ 8.87 $ 7.30 21.53%
$ 11.06 $ 10.62 4.17%
$ 49.30 $ 13.94 253.66%
$ 17.19 $ 17.26 -0.42%
$ 19.38 $ 20.58 -5.83%
$ 21.57 $ 23.90 -9.75%
$ 28.53 $ 27.22 4.83%
$ 30.73 $ 30.54 0.61%
$ 68.32 $ 48.80 39.99%
$ 95.71 $ 90.30 5.99%
$ 1,411.71 $ 1,667.30 -15.33%
$ 11,273.24 $ 16,607.30 -32.12%
$ 109,888.47 $ 166,007.30 -33.81%
$ 14,002.67 $ 16,618.65 -15.74%
$ 59,465.23 $ 83,018.65 -28.37%
$ 110,154.67 $ 166,018.65 -33.65%
...J =NJ r...ii ...i .rrJ Ewa _ J ..,d road eeeei um! M IMMO I.reO W il■er O
Alternative 2(a)
Wet Weather Flow Percentage
Factors Utilized:
Ill Allocation
Capacity
Volume
Customer Description
City Residence
City Residence
City Church
Original District Residence
Original District Residence
Original District Residence
Annexed Area Residence
Annexed Area Residence
Tax Exempt - Annexed Area
Tax Exempt - Annexed Area
High Rise Commercial
High Rise Commercial
High Rise Commercial
Crestwood Mall - Commercial
Chesterfield Mall - Commercial
Industrial
Alternative 2(a)
33%
60%
40%
Imprevious
Area
1,833
1,833
21,636
2,790
2,790
2,790
5,412
5,412
19,442
19,442
170,557
170,557
170,557
1,663,820
2,561,271
310,567
Typical Billing Summary
Monthly Bill CCF Monthly Bill
$ 0 $
$ 2 $
$ 4 $
$ 6 $
$ 8 $
$ 10 $
$ 12 $
$ 14 $
$ 25 $
$ 50 $
$ 1000 $
$ 10,000 $
$ 100,000 $
$ 10,000 $
$ 50,000 $
$ 100,000 $
9.32
12.35
15.38
18.42
21.45
24.49
27.52
30.56
47.24
85.17
1,526.46
15,180.74
151, 723.55
15,192.09
75, 877.79
151, 734.90
Combined Bill Existing Bill Variance
$ 9.32 $ 7.30 27.62%
$ 12.35 $ 10.62 16.30%
$ 15.38 $ 13.94 10.37%
$ 18.42 $ 17.26 6.72%
$ 21.45 $ 20.58 4.24%
$ 24.49 $ 23.90 2.46%
$ 27.52 $ 27.22 1.11%
$ 30.56 $ 30.54 0.05%
$ 47.24 $ 48.80 -3.19%
$ 85.17 $ 90.30 -5.68%
$ 1,526.46 $ 1,667.30 -8.45%
$ 15,180.74 $ 16,607.30 -8.59%
$ 151,723.55 $ 166,007.30 -8.60%
$ 15,192.09 $ 16,618.65 -8.58%
$ 75,877.79 $ 83,018.65 -8.60%
$ 151,734.90 $ 166,018.65 -8.60%
a•i mod mama Mini mod Nail reimi Imo
ow Imo Imo Warn ions
Alternative 2(b)
Wet Weather Flow Percentage
Factors Utilized:
Ill Allocation
Capacity
Volume
Customer Description
City Residence
City Residence
City Church
Original District Residence
Original District Residence
Original District Residence
Annexed Area Residence
Annexed Area Residence
Tax Exempt - Annexed Area
Tax Exempt - Annexed Area
High Rise Commercial
High Rise Commercial
High Rise Commercial
Crestwood Mall - Commercial
Chesterfield Mall - Commercial
Industrial
Alternative 2(b)
33%
60%
40%
lmprevious
Area
1,833
1,833
21,636
2,790
2,790
2,790
5,412
5,412
19,442
19,442
170,557
170,557
170,557
1,663,820
2,561,271
310,567
Typical Billing Summary
Monthly Bill
$ 1.77
$ 1.77
$ 20.90
$ 2.69
$ 2.69
$ 2.69
$ 5.23
$ 5.23
$ 18.78
$ 18.78
$ 164.73
$ 164.73
$ 164.73
$ 1,606.94
$ 2,473.71
$ 299.95
CCF Monthly Bill Combined Bill Existing Bill Variance
0 $ 9.32 $ 11.09 $ 7.30 51.87%
2 $ 11.66 $ 13.43 $ 10.62 26.43%
4 $ 14.00 $ 34.89 $ 13.94 150.31%
6 $ 16.34 $ 19.03 $ 17.26 10.27%
8 $ 18.68 $ 21.37 $ 20.58 3.85%
10 $ 21.02 $ 23.71 $ 23.90 -0.78%
12 $ 23.36 $ 28.59 $ 27.22 5.02%
14 $ 25.70 $ 30.93 $ 30.54 1.27%
25 $ 38.57 $ 57.35 $ 48.80 17.52%
50 $ 67.83 $ 86.60 $ 90.30 -4.09%
1000 $ 1,179.53 $ 1,344.26 $ 1,667.30 -19.38%
10,000 $ 11,711.46 $ 11,876.19 $ 16,607.30 -28.49%
100,000 $ 117,030.78 $ 117,195.51 $ 166,007.30 -29.40%
10,000 $ 11,722.82 $ 13,329.76 $ 16,618.65 -19.79%
50,000 $ 58,531.40 $ 61,005.12 $ 83,018.65 -26.52%
100,000 $ 117,042.14 $ 117,342.09 $ 166,018.65 -29.32%
anal sommi smi a mat w mai >✓ ummil - mod =I-INNOr Um s um
Alternative 2(c)
Wet Weather Flow Percentage
Factors Utilized:
Ill Allocation
Capacity
Volume
Customer Description
City Residence
City Residence
City Church
Original District Residence
Original District Residence
Original District Residence
Annexed Area Residence
Annexed Area Residence
Tax Exempt - Annexed Area
Tax Exempt - Annexed Area
High Rise Commercial
High Rise Commercial
High Rise Commercial
Crestwood Mall - Commercial
Chesterfield Mail - Commercial
Industrial
Alternative 2(c)
33%
60%
40%
imprevious
Area
1,833
1,833
21,636
2,790
2,790
2,790
5,412
5,412
19,442
19,442
170,557
170,557
170,557
1,663,820
2,561,271
310,567
Typical Billing Summary
Monthly Bill
$ 2.42
$ 2.42
$ 28.60
$ 3.69
$ 3.69
$ 3.69
$ 7.15
$ 7.15
$ 25.70
$ 25.70
$ 225.46
$ 225.46
$ 225.46
$ 2,199.38
$ 3,385.70
$ 410.53
CCF Monthly Bill Combined Bill Existing Bill Variance
0 $ 8.45
2 $ 10.64
4 $ 12.83
6 $ 15.02
8 $ 17.21
10 $ 19.40
12 $ 21.60
14 $ 23.79
25 $ 35.84
50 $ 63.23
1000 $ 1,104.17
10,000 $ 10,965.69
100,000 $ 109,580.92
10,000 $ 10,977.05
50,000 $ 54,806.04
100,000 $ 109,592.27
$ 10.87 $ 7.30 48.91%
$ 13.06 $ 10.62 22.99%
$ 41.43 $ 13.94 197.21%
$ 18.71 $ 17.26 8.40%
$ 20.90 $ 20.58 1.56%
$ 23.09 $ 23.90 -3.38%
$ 28.75 $ 27.22 5.62%
$ 30.94 $ 30.54 1.31%
$ 61.54 $ 48.80 26.11
$ 88.93 $ 90.30 -1.51%
$ 1,329.63 $ 1,667.30-20.25%
$ 11,191.15 $ 16,607.30 -32.61%
$ 109,806.37 $ 166,007.30 -33.85%
$ 13,176.43 $ 16,618.65 -20.71%
$ 58,191.74 $ 83,018.65 -29.91%
$ 110,002.81 $ 166,018.65 -33.74%
.sue MIA ■J mod NNW mai mil — ..r am — Nis
Alternative 3(a)
Wet Weather Flow Percentage
Factors Utilized:
Ill Allocation
Capacity
Volume
Customer Description
City Residence
City Residence
City Church
Original District Residence
Original District Residence
Original District Residence
Annexed Area Residence
Annexed Area Residence
Tax Exempt - Annexed Area
Tax Exempt - Annexed Area
High Rise Commercial
High Rise Commercial
High Rise Commercial
Crestwood Mall - Commercial
Chesterfield Mall - Commercial
Industrial
Alternative 3(a)
33%
24%
76%
Imprevious
Area
1,833
1,833
21,636
2,790
2,790
2,790
5,412
5,412
19,442
19,442
170,557
170,557
170,557
1,663,820
2,561,271
310,567
Typical Billing Summary
Monthly Bill CCF Monthly Bill Combined Bill Existing Bill Variance
$ 0 $ 4.24 $ 4.24 $ 7.30 -41.97%
$ - 2 $ 7.90 $ 7.90 $ 10.62 -25.66%
$ 4 $ 11.55 $ 11.55 $ 13.94 -17.12%
$ 6 $ 15.21 $ 15.21 $ 17.26 -11.86%
$ 8 $ 18.87 $ 18.87 $ 20.58 -8.30%
$ 10 $ 22.53 $ 22.53 $ 23.90 -5.73%
$ 12 $ 26.19 $ 26.19 $ 27.22 -3.79%
$ 14 $ 29.85 $ 29.85 $ 30.54 -2.27%
$ - 25 $ 49.97 $ 49.97 $ 48.80 2.40%
$ 50 $ 95.71 $ 95.71 $ 90.30 5.99%
$ 1000 $ 1,833.61 $ 1,833.61 $ 1,667.30 9.98%
$ 10,000 $ 18,298.01 $ 18,298.01 $ 16,607.30 10.18%
$ 100,000 $ 182,941.96 $ 182,941.96 $ 166,007.30 10.20%
$ 10,000 $ 18,309.36 $ 18,309.36 $ 16,618.65 10.17%
$ 50,000 $ 91,484.45 $ 91,484.45 $ 83,018.65 10.20%
$ 100,000 $ 182,953.31 $ 182,953.31 $ 166,018.65 10.20%
ommi somil mad ma mod semi NNW owl mil mosi nog loosi IN= 11•0 MN UM
Alternative 3(b)
Wet Weather Flow Percentage
Factors Utilized:
Ill Allocation
Capacity
Volume
Customer Description
City Residence
City Residence
City Church
Original District Residence
Original District Residence
Original District Residence
Annexed Area Residence
Annexed Area Residence
Tax Exempt - Annexed Area
Tax Exempt - Annexed Area
High Rise Commercial
High Rise Commercial
High Rise Commercial
Crestwood Mall - Commercial
Chesterfield Mall - Commercial
Industrial
Alternative 3(b)
33%
24%
76%
Imprevious
Area
1,833
1,833
21,636
2,790
2,790
2,790
5,412
5,412
19,442
19,442
170,557
170,557
170,557
1,663,820
2,561,271
310,567
Typical Billing Summary
Monthly Bill
$ 3.36
$ 3.36
$ 39.70
$ 5.12
$ 5.12
$ 5.12
$ 9.93
$ 9.93
$ 35.68
$ 35.68
$ 312.98
$ 312.98
$ 312.98
$ 3,053.19
$ 4,700.06
$ 569.91
CCF Monthly Bill Combined Bill Existing Bill Variance
0 $ 4.24 $ 7.60 $ 7.30 4.11%
2 $ 6.58 $ 9.94 $ 10.62 -6.40%
4 $ 8.92 $ 48.62 $ 13.94 248.78%
6 $ 11.26 $ 16.38 $ 17.26 -5.11%
8 $ 13.60 $ 18.72 $ 20.58 -9.05%
10 $ 15.94 $ 21.06 $ 23.90 -11.89%
12 $ 18.28 $ 28.21 $ 27.22 3.64%
14 $ 20.62 $ 30.55 $ 30.54 0.04%
25 $ 33.49 $ 69.17 $ 48.80 41.74%
50 $ 62.75 $ 98.42 $ 90.30 9.00%
1000 $ 1,174.45 $ 1,487.43 $ 1,667.30 -10.79%
10,000 $ 11,706.38 $ 12,019.36 $ 16,607.30 -27.63%
100,000 $ 117,025.68 $ 117,338.66 $ 166,007.30 -29.32%
10,000 - $ 11,717.74 $ 14,770.93 $ 16,618.65 -11.12%
50,000 $ 58,526.31 $ 63,226.37 $ 83,018.65 -23.84%
100,000 $ 117,037.04 $ 117,606.94 $ 166,018.65 -29.16%
and Nummil ma mod mid mad ma end sod mai nod mod Immi NNW =NI ono mow Nom
Alternative 3(c
Wet Weather Flow Percentage
Factors Utilized: Alternative 3(c)
Ill Allocation 33%
Capacity 24%
Volume 76%
Typical Billing Summary
Imprevious
Customer Description Area Monthly Bill CCF Monthly Bill Combined Bill Existing Bill Variance
City Residence 1,833 $ 3.85 0 $ 3.89 $ 7.74 $ 7.30 6.05%
City Residence 1,833 $ 3.85 2 $ 6.08 $ 9.93 $ 10.62 -6.47%
City Church 21,636 $ 45.48 4 $ 8.27 $ 53.75 $ 13.94 285.57%
Original District Residence 2,790 $ 5.86 6 $ 10.46 $ 16.33 $ 17.26 -5.40%
Original District Residence 2,790 $ 5.86 8 $ 12.65 $ 18.52 $ 20.58 -10.01%
Original District Residence 2,790 $ 5.86 10 $ 14.85 $ 20.71 $ 23.90 -13.35%
Annexed Area Residence 5,412 $ 11.38 12 $ 17.04 $ 28.41 $ 27.22 4.38%
Annexed Area Residence 5,412 $ 11.38 14 $ 19.23 $ 30.60 $ 30.54 0.21%
Tax Exempt - Annexed Area 19,442 $ 40.87 25 $ 31.28 $ 72.15 $ 48.80 47.84%
Tax Exempt - Annexed Area 19,442 $ 40.87 50 $ 58.68 $ 99.54 $ 90.30 10.23%
High Rise Commercial 170,557 $ 358.49 1000 $ 1,099.61 $ 1,458.11 $ 1,667.30 -12.55%
High Rise Commercial 170,557 $ 358.49 10,000 $ 10,961.13 $ 11,319.63 $ 16,607.30 -31.84%
High Rise Commercial 170,557 $ 358.49 100,000 $ 109,576.34 $ 109,934.84 $ 166,007.30 -33.78%
Crestwood Mall - Commercial 1,663,820 $ 3,497.19 10,000 $ 10,972.49 $ 14,469.67 $ 16,618.65 -12.93%
Chesterfield Mall - Commercial 2,561,271 $ 5,383.54 50,000 $ 54,801.47 $ 60,185.01 $ 83,018.65 -27.50%
Industrial 310,567 $ 652.78 100,000 $ 109,587.69 $ 110,240.48 $ 166,018.65 -33.60%
aid owel coal gasimJ gel wool _
Table C-1
Standard Deviation Calculations
1. Inter -Class
1a
1b
lc
2a
2b
2c
3a
3b
3c
Single Family
-0.61
-0.31
-0.31
0.86
1.05
1.05
-1.44
-1.08
-1.08
Multi Family
0.83
-6.72
-6.72
-1.48
-6.27
-6.27
2.13
-6.98
-6.98
Non -Residential All Other
7.1
16.01
16.01
-9.42
-3.76
-3.76
16.44
27.19
27.19
1. Standard Deviation
4.099
11.720
11.720
5.388
3.720
3.720
9.462
18.265
18.265
Score (10 highest)
9.00
5.00
5.00
7.00
8.00
8.00
6.00
4.00
4.00
2. Intra-Class
Single Family
City Residence - 0 ccf
-1.16
1.34
1.34
1.75
3.34
3.34
-2.8
0.21
0.21
City Residence - 2 ccf
-1.03
0.49
0.49
1.53
2.49
2.49
-2.47
-0.64
-0.64
City Residence - 4 ccf
-0.89
-0.35
-0.35
1.3
1.64
1.64
-2.13
-1.48
-1.48
Original D. Res. - 6 ccf
-0.75
0.11
0.11
1.09
1.63
1.63
-1.79
-0.75
-0.75
Original D. Res. - 8 ccf
-0.62
-0.73
-0.73
0.86
0.79
0.79
-1.45
-1.59
-1.59
Original D. Res. - 10 ccf
-0.48
-1.57
-1.57
0.65
-0.05
-0.05
-1.11
-2.43
-2.43
Annexed Area Res - 12 ccf
-0.34
1.16
1.16
0.42
1.37
1.37
-0.78
1.04
1.04
Annexed Area Res - 14 ccf
-0.2
0.32
0.32
0.2
0.54
0.54
-0.43
0.2
0.2
2.a. Standard Deviation -Single Family
0.336
0.967
0.967
0.542
1.085
1.085
0.829
1.138
1.138
Multi Family
0
0
0
0
0
0
0
0
0
2.b. Standard Deviation - Multi -Family
0.83
-6.72
-6.72
-1.48
-6.27
-6.27
2.13
-6.98
-6.98
Standard Deviation
0.587
4.752
4.752
1.047
4.434
4.434
1.506
4.936
4.936
Non -Residential All Other
Tax Exempt - Annexed Area - 25 ccf
0.55
14.82
14.82
-1.01
8.05
8.05
1.43
18.64
18.64
Tax Exempt - Annexed Area - 50 ccf
2.27
4.29
4.29
-3.77
-2.48
-2.48
5.68
8.11
8.11
High Rise Commercial - 1000 ccf
67.32
-189.96
-189.96
-108.62
-271.97
-271.97
166.77
-143.61
-143.61
2.c. Standard Deviation Non -Res
38.063
115.310
115.310
61.347
158.717
158.717
94.256
90.788
90.788
2.a. b. c. Standard Deviation - Weighted
2.615
8.186
8.186
4.224
10.843
10.843
6.477
6.884
6.884
Score (10 highest)
9.00
5.00
5.00
8.00
4.00
4.00
7.00
6.00
6.00
3. Class Equity - Average of 1 and 2
9.00
5.00
5.00
7.50
6.00
6.00
6.50
5.00
5.00
4. Rate Impact
Single Family Residential Bills Variance
1a
1b
1c
2a
2b
2c
3a
3b
3c
0
0
0
0
0
0
0
0
0
Single Family
-0.61
-0.31
-0.31
0.86
1.05
1.05
-1.44
-1.08
-1.08
Standard Deviation
0.431
0.219
0.219
0.608
0.742
0.742
1.018
0.764
0.764
Score (10 highest)
8.00
9.00
9.00
7.00
6.00
6.00
4.00
5.00
5.00
Table C-2
Summary of Weighted Scores
Rate Admin
Rate Impact Methodology Class Equity Simplicity Total
A 10 2 10 8
A weighted 2.00 0.80 3.00 0.80 6.60
1 (a) 8 4 9 8
1 (a) weighted 1.60 1.60 2.70 0.80 6.70
1 (b) 9 6 5 2
1 (b) weighted 1.80 2.40 1.50 0.20 5.90
1 (c) 9 8 5 8
1 (c) weighted 1.80 3.20 1.50 0.80 7.30
2 (a) 7 4 7.5 8
2 (a) weighted 1.40 1.60 2.25 0.80 6.05
2 (b) 6 8 6 2
2 (b) weighted 1.20 3.20 1.80 0.20 6.40
2 (c) 6 10 6 8
2 (c) weighted 1.20 4.00 1.80 0.80 7.80
3 (a) 4 2 6.5 6
3 (a) weighted 0.80 0.80 1.95 0.60 4.15
3 (b) 5 6 5 2
3 (b) weighted 1.00 2.40 1.50 0.20 5.10
3 (c) 5 8 5 6
3 (c) weighted 1.00 3.20 1.50 0.60 6.30
Max Point Score 10 10 10 10
Weight Factors 20% 40% 30% 10% 100%
Max Weighted Score 2.00 4.00 3.00 1.00 10.00
Table C-3
Summary of Weighted Alternatives
1
1
1
i
t
t
t
t
Alternatives
Rate Impact
Rate
Methodology
Class Equity
Admin
Simplicity
Total
Rank
2 (c) weighted
1.20
4.00
1.80
0.80
7.80
1
1 (c) weighted
1.80
3.20
1.50
0.80
7.30
2
1 (a) weighted
1.60
1.60
2.70
0.80
6.70
3
A weighted
2.00
0.80
3.00
0.80
6.60
4
2 (b) weighted
1.20
3.20
1.80
0.20
6.40
5
3 (c) weighted
1.00
3.20
1.50
0.60
6.30
6
2 (a) weighted
1.40
1.60
2.25
0.80
6.05
7
1 (b) weighted
1.80
2.40
1.50
0.20
5.90
8
3 (b) weighted
1.00
2.40
1.50
0.20
5.10
9
3 (a) weighted
0.80
0.80
1.95
0.60
4.15
10
Table C-4
Billable Units of Service Related to Functional Cost Elements
H-11
Table Ref.
Percent Customer
H-5 Customer Related
H-5 Volume Related
H-5 45% of Total Treated
I/1
Capacity
I/I
37%
25,353,900
43,170,100
37%
291,049
495,570
68,524,000 786,619 (4.19 times I/I volume/365)
H-5 Total Treated 152,275,600
H-7 Volume Related Capacity
H-7 Total Capacity
Percent Customer
Customer Related
Volume Related
396,960 (1.73 times contrib. volume/365)
1,183,579
BOD
I/I
TSS
Ill
37%
3,955,226
6,734,574
37%
7,910,415
13,469,085
H-6 Normal Loading x I/I Vol. 10,689,800 21,379,500
H-6 Normal Loading x Contrib Vol 107,135,000 112,361,100
B-9 & H-6 Extra Strength 24,600,000 19,150,400
Total Loadings 142,424,800 152,891,000
1
Table C-5
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1
1
1
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1
a
1
t
1
Calculation of Unit Costs -Revised Existing A
Less: Stormwater
Table H-9 ccf/day
Cost/ccf
System Availability Charge
Customer Related Cap. I/1
Balance of Costs
Equivalent Bills
System Availability Charge - $/Bill
Volume Charqe
Volume Related Capacity
Volume Related I/I Capacity
Balance of Costs
Equivalent Billable Volume - ccf
Capacity
Cost - Revised
Capacity
Cost - Existing
$118,012,400
(13,657,600)
$104,354,800
1,183,579
$118,012,400
1,183,579
$88.16885 $99.70809
Revised Cost
Existing Cost
291,049 88.16885 $25,661,458 $29,019,943
4,343,833 4,343,833
396,960 88.16885
495,570 88.16885
Difference
($3,358,484)
$30,005,291 $33,363,776 ($3,358,484)
5,134,082 5,134,082
$5.84433 $6.49849
$34,999,507
43,693,835
48,085,335
$39,580,123 ($4,580,616)
49,412,335 (5,718,500)
48,085,335
$126,778,677 $137,077,792
83,527,350 83,527,350
$1.51781 $1.64111
($13,657,600)
1
1
Table C-6
I
Table H-5
fable H-5
,Table H-5
tingle Family
Multi -Family
!Ion -Residential
Revisions per Customer Class - Existing A
Bills Volume
Single Family 4,291,185 34,473,150
Multi -Family 534,925 15,597,100
Non -Residential 307,972 33,457,100
5,134,082 83,527,350
Billing Charge
Avail. Charge
$1.13557 $5.84440
Volume Charge
Extra S.
Compliance
$11.35375
Total
Bills
New
$82,276,379 4,291,185 $19.17
$607,445 $3,126,316 $23,673,590 $27,407,351 534,925 $51.24
$349,724 $1,799,912 $50,781,856 $6,571,687 $3,496,637 $62,999,815 307,972 $204.56
$5,830,109 $30,005,629 $126,779,482 $6,571,687 $3,496,637 $172,683,545
allocated Costs $5,830,100 $30,005,300 $126,778,716 $6,571,687 $3,496,500 $172,682,303
$4,872,941 $25,079,402
$1.5178
$52,324,037
I
I
Table H-5 Single Family
able H-5 Multi -Family
table H-5
'tingle Family
Multi -Family
lon-Residential
Lflocated Cost
Non -Residential
Revisions per Customer Class - 1(a)
Bills Volume
4,291,185
534,925
307,972
Table C-7
34,473,150
15,597,100
33,457,100
5,134,082
83,527,350
Billing Charge
Avail. Charge
Volume Charge
Extra S.
Compliance
Total
Bills
New
$1.13557
$4,872,941
$4.68087
$20,086,479
$607,445 $2,503,914
$349,724 $1,441,577
$5,830,109 $24,031,970
$5,830,100 $24,031,977
$1.58630
$54,684,758
$24,741,680
$53,072,998
$132,499,435
$132,499,510
$6,824,212
$6,824,212
$6,824,212
$11.35375
$3,496,637
$3,496,637
$3,496,500
$79,644,178
$27,853,039
$65,185,147
$172,682,364
$172,682,299
4,291,185
534,925
307,972
$18.56
$52.07
$211.66
Table C-8
I Revisions per Customer Class -1(b) and 1(c)
Bills Volume Imp Area
Table H-5 Single Family 4,291,185 34,473,150 1,111,065,766
able H-5 Multi -Family 534,925 15,597,100 220,046,834
Table H-5 Non -Residential 307,972 33,457,100
5,134,082 83,527,350 2,500,300,811
IBilling Charge I Avail. Charge J Volume Charge I Extra S. I Compliance I Imp Area I Total I Bills I New
$1.13557 $4.68087 $1.09641 $11.35375 $0.016366
Single Family $4,872,941 $20,086,479 $37,796,706 18,183,702 $80,939,829 4,291,185 $18.86
tulti-Family $607,445 $2,503,914 $17,100,816 3,601,286 $23,813,462 534,925 $44.52
Non -Residential $349,724 $1,441,577 $36,682,699 $6,824,212 $3,496,637 19,134,934 $67,929,783 307,972 $220.57
II$5,830,109 $24,031,970 $91,580,222 $6,824,212 $3,496,637 $40,919,923 $172,683,074
Allocated Cost $5,830,100 $24,031,977 $91,580,197 $6,824,212 $3,496,500 $40,919,313 $172,682,299
1,169,188,211
t
t
i
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t
t
i
t
I
I
Table H-5
fable H-5 Multi -Family
Table H-5
tingle Family
Multi -Family
Ion -Residential
Revisions per Customer Class - 2(a)
Bills Volume
Single Family
Non -Residential
4,291,185
534,925
307,972
Table C-9
34,473,150
15,597,100
33,457,100
5,134,082
83,527,350
Billing Charge
$1.13557
$4,872,941
Avail. Charge
$7.5906
$32,572,669
$607,445 $4,060,402
$349,724 $2,337,692
$5,830,109 $38,970,763
allocated Cost $5,830,100 $38,970,773
i
1
1
1
i
1
1
1
1
I
1
Volume Charge
$1.41
$48,519,235
$21,952,138
$47,089,195
$117,560,569
$117,560,713
Extra S. I Compliance
$6,824,212
$6,824,212
$6,824,212
$11.35375
$3,496,637
$3,496,637
$3,496,500
Total
$85,964,845
$26,619,985
$60,097,461
$172,682,290
$172,682,298
Bills
4,291,185
534,925
307,972
New
$20.03
$49.76
$195.14
Table C-10
I
Table H-5
ITable H-5
Table H-5
I
Single Family
'Multi -Family
Non -Residential
I
Allocated Cost
I
1
1
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i
t
t
t
1
Revisions per Customer Class - 2(b) and 2(c)
Bills Volume
Single Family 4,291,185 34,473,150
Multi -Family
Non -Residential
I Billing Charge I
$1.13557
$4,872,941
$607,445
$349,724
$5,830,109
$5,830,100
534,925 15,597,100
Imp Area
1,111,065,766
220,046,834
307,972 33,457,100 I 1,169,188,211
5,134,082 83,527,350 2,500,300,811
Avail. Charge I Volume Charge I
$7.5906
$32,572,669
$4,060,402
$2,337,692
$38,970,763
$38,970,773
$1.09641
$37,796,706
$17,100,816
$36,682,699
$91,580,222
$91,580,197
Extra S. I Compliance I Imp Area I Total
$6,824,212
$6,824,212
$6,824,212
S11.35375
$3,496,637
$3,496,637
$3,496,500
$0.010391
11,545,084
2,286,507
12,149,035
$25,980,626
$25,980,516
$86,787,401
$24,055,170
$61,839,999
$172,682,569
$172,682,298
Bills
4,291,185
534,925
307,972
New
$20.22
$44.97
$200.80
1
Table C-11
I Revisions per Customer Class - 3(a)
Bills Volume
Table H-5 Single Family 4,291,185 34,473,150
'able H-5 Multi -Family 534,925 15,597,100
Table H-5 Non -Residential 307,972 33,457,100
1
Billing Charge
$1.13557 $3.0362 $1.69 $11.35375
tingle Family $4,872,941 $13,029,068 $58,169,649 $76,071,657 4,291,185 $17.73
Multi -Family $607,445 $1,624,161 $26,318,391 $28,549,996 534,925 $53.37
Ilion -Residential $349,724 $935,077 $56,455,176 $6,824,218 $3,496,637 $68,060,832 307,972 $221.00
$5,830,109 $15,588,305 $140,943,215 $6,824,218 $3,496,637 $172,682,485
allocated Cost $5,830,100 $15,588,303 $140,943,179 $6,824,212 $3,496,500 $172,682,294
5,134,082 83,527,350
Avail. Charge
Volume Charge
Extra S.
Compliance
Total
Bills
New
Table C-12
I
Table H-5
able H-5
able H-5
Revisions per Customer Class - 3(b) and 3(c)
Bills Volume Imp Area
Single Family 4,291,185 34,473,150 1,111,065,766
Multi -Family 534,925 15,597,100 220,046,834
307,972 33,457,100
5,134,082 83,527,350 2,500,300,811
IBilling Charge J Avail. Charge I Volume Charge I Extra S. I Compliance I Imp Area I Total I Bills I New
$1.13557 $3.0362 $1.09641 $11.35375 $0.019743
Single Family $4,872,941 $13,029,068 $37,796,706 21,935,771 $77,634,486 4,291,185 $18.09
ltult.F8milY $607,445 $1,624,161 $17,100,816 4,344,385 $23,676,807 534,925 $44.26
Non -Residential $349,724 $935,077 $36,682,699 $6,824,218 $3,496,637 23,083,283 $71,371,638 307,972 $231.75
I$5,830,109 $15,588,305 $91,580,222 $6,824,218 $3,496,637 $49,363,439 $172,682,930
Allocated Cost $5,830,100 $15,588,303 $91,580,220 $6,824,218 $3,496,500 $49,362,958 $172,682,299
1,169,188,211
1
1
1
1
1
1
1
1
1
1
1
1
1
Non -Residential
t
1
1
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1
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t
t
t
i
Appendix D
Glossary
Average Annual Flow - The flow volume over a calendar year based on an averaging
of a single or multiple 365 day period.
Ccf - Volume measurement equal to 100 cubic feet (748-gallons) of wastewater.
Combined Sewer Overflow (CSO) - Flow from combined sewer system, in excess of
sewer capacity, that is discharged to a waterbody without treatment.
Combined Sewer System - Combined sewer systems are sewers that are designed to
collect rainwater runoff, domestic sewage, and industrial wastewater in the same
pipe.
Dry Weather Flow - Non -storm flow that consists of the average sewage flow and
average dry weather infiltration/inflow.
Equivalent Length (inch -feet of pipe) - A means of calculating pipe equivalency by
multiplying the pipe diameter by the length of pipe.
Impervious Area - Impermeable surfaces, such as pavement or rooftops, which
impede natural infiltration of water to the soil.
Infiltration/Inflow (I/I) - Infiltration is water that enters sewer pipes through cracks
and joints. Also, the movement of water downward from the ground surface through
the upper soil. Inflow is surface water entering the sanitary sewer system through
illicit connections, roof drains, open or defective manholes, etc.
Sanitary Sewer System - A sanitary sewer system is a wastewater collection system,
owned by a state or municipality, that is specifically designed to collect and convey
only sanitary wastewater (domestic sewage from homes as well as industrial and
commercial wastewater).
Sanitary Sewer Overflow (SSO) - Discharge of sewage from a separate sewer system
when the collection system capacity is exceeded due to wet weather (as the result of
infiltration and inflow), when normal dry weather flow is blocked for any of several
reasons, or when mechanical failures prevent the system from proper operation.
Separate Sewer System -A sewer system and drains in which sanitary wastewater
and storm water are carried in different conduits.
Sf - Measurement of the total impervious area by square feet.
Surface Runoff - Rainfall dependent flow over the surface, after infiltration,
interception, and surface storage occurred.
System Availability Charge - is a charge per the equivalent number of bills used to
recover customer related Inflow/Infiltration costs.
Volume Recovery Charge - is a charge per hundred cubic feet (Ccf) used to recover
volume related costs.
D-1
Wet Weather Flow - In a separate sewer system, wet weather flow is a combination of
dry weather flow, inflow and infiltration which occurs as a result of rain and storms.
In a combined sewer system, wet weather flow is a combination of dry weather flow,
surface runoff captured by the sewer system, and infiltration.
D-2
1
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