Presentation to Town of Fairfax,
September 2, 2026
Ross Valley Sanitary District Facts
15,900
customers
199
Miles of
gravity
main
19 Pump
stations
7 Miles of
force
main
45%
of Sewers
Installed
before
1955
44,946
Population
4 Incorporated Cities &
Towns
Fairfax, San Anselmo,
Ross, Larkspur
4 Unincorporated Areas
Kentfield, Greenbrae,
Sleepy Hollow, Oak Manor
$44 M
Investment
last 5 years
CMSA JPA
• Three JPA Members
• Ross Valley Sanitary District
(RVSD)
• San Rafael Sanitation District
(SRSD)
• Sanitary District No. 2 (SD2,
Corte Madera)
• CMSA Governance (5 Seats)
• RVSD 2, SRSD 2, SD2 1
• City of Larkspur gave up
“sixth” CMSA seat in 2019
50%
38%
12%
CMSA JPA POPULATIONS*
RVSD SRSD SD2
*Population estimates from CMSA 24-25 Budget, needs validation Treatment Cost is Related to the
Strength of the Wastewater
• Strength measured by BOD=biochemical oxygen demand
(organic content), and TSS=total suspended solids
• Stronger concentrated wastewater costs more to treat
• Energy for Aeration Blowers, Solids Handling and Trucking, Chemicals • RVSD has the lowest strength wastewater measured by CMSA 0 50
100
150
200
250
300
RVSD SRSD SD2 SQSP
Wastewater Strength Average Concentrations
2024-2026
3-Yr Avg BOD (mg/L) 3-Yr Avg TSS (mg/L)
CMSA Changes the Allocation Formula
• In April 2026, on a 3-2 vote with RVSD
commissioners dissenting, CMSA changed from
Flow-Strength to Flow-only, increasing RVSD’s
annual charge by about $500,000
• This change occurred less than a year after RVSD identified large errors in CMSA’s strength measurements
• No technical reports or analysis
• Increased annual payment from $7 Million in 2025-26 to almost $8 Million in 2026-27
• This change restored an allocation percentage that had been based on bad strength data which RVSD uncovered
in 2025
Facts about Treatment Cost Allocations
• RVSD has lower wastewater strength than
SRSD, SD2 and San Quentin
• RVSD costs less to treat per gallon
• No other JPA’s or Similar Agencies to CMSA in
California use Flow-only (unless by original
agreement documents from 1970s) – WRE
Consultants, July 2026
• Flow-Strength is the modern industry standard
0 200
400
600
800
1,000
1,200
1,400
1,600
1,800
2,000
CMSA Strength Measurements 2018-2026
San Rafael BOD mg/L San Rafael TSS mg/L Ross Valley BOD mg/L Ross Valley TSS mg/L JUNE 2023
INTERCEPTOR SAMPLING PORTS
CHANGED FROM
5 O'CLOCK TO 3 O'CLOCK
CMSA DID NOT TELL JPA MEMBERS,
BUT IT SIGNIFICANTLY CHANGED THE
TREATMENT CHARGES
2018 2020 2022 2024 2026
0 100
200
300
400
500
Median April 2018-June 2023 Median July 2023-March 2026 CMSA Strength Measurements
Median Values
Before and After June 2023
(Sampling Location Change)
San Rafael BOD mg/L San Rafael TSS mg/L
Ross Valley BOD mg/L Ross Valley TSS mg/L
0 100
200
300
400
500
Standard Deviation April 2018-June
2023
Standard Deviation July 2023-March
2026
CMSA Strength Measurements
Standard Deviation Values
Before and After June 2023
(Sampling Location Change)
San Rafael BOD mg/L San Rafael TSS mg/L
Ross Valley BOD mg/L Ross Valley TSS mg/L
TYPICAL WASTEWATER VALUES:
BOD <300 mg/L
TSS <350 mg/L source: Metcalf & Eddy, 1972
Before June 2023, Medians were
Above the Maximum Literature Values,
And Standard Deviations (Variability)
Were Much Higher
June 2023 sampling change made data accurate,
And RVSD was over-charged for 10 years
TSS max. 350 mg/L
BOD max. 300 mg/L
BAD DATA
BAD DATA
RVSD calls on CMSA to:
• Consider restoring the Flow-Strength allocation formula used 2013-2026 • Provide third-party objective technical report
• Resolve Dispute regarding paying back RVSD the
over-charges
• Implement Quality Assurance and Transparency
Recommendations on Sampling, Calculation and
Reporting
• Consider structural changes to the JPA, e.g.,
• Restore the Larkspur Seat on the CMSA Board to RVSD,
totaling 3 seats, to equitably represent populations served • Modify JPA agreement to require super-majority vote for major financial decisions