Southern Marin WWTP
450 Sycamore Avenue, Mill Valley, CA 94941 · Marin County · Publicly Owned Treatment Works
- Average flow
- —
- Design flow
- 24.7 MGD
- NPDES permit
- CA0037711
- Effective
- Permit expires
- December 2028
- Population served
- 30,981
- CWNS 2022
Southern Marin WWTP is a publicly owned wastewater treatment works in Mill Valley, Marin County, California, serving about 30,981 residents. It discharges under NPDES permit CA0037711 (effective), which expires in December 2028, with 9 recorded violations in the last three years. EPA has recorded 1 formal enforcement action naming the plant, the latest in November 2024.
Treatment technology
3 treatment structures and unit processes identified at Southern Marin WWTP.
Available with a free Klarifi account
See the full treatment train at Southern Marin WWTP: structures, unit processes and planned upgrades, with exact unit counts.
Compliance snapshot (last 3 years)
- Total violations
- 9
- Effluent violations
- 9
Based on NPDES Discharge Monitoring Reports. Full violation history, parameters and discharge data available in the Klarifi platform.
EPA enforcement history
Federal civil enforcement cases, compliance inspections and informal actions recorded for Southern Marin WWTP in EPA's ICIS system.
- Formal actions
- 1
- 0 since FY2020
- Compliance actions
- $1M
- required by EPA orders
- EPA inspections
- 0
- none on record
Latest case · Nov 2024
Sewerage Agency of Southern Marin SASM Administrative Order
Administrative order · CWA, NPDES Discharge without a Permit · Final Order No Penalty · Compliance actions $1M
EPA's description of the case:
“This is an Administrative Order (AO) for compliance pursuant to CWA 309(a) issued to Sewerage Agency of Southern Marin, Almonte Sanitary District, Alto Sanitary District, City of Mill Valley,…”
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Source: EPA ECHO, civil enforcement case 09-2008-1506.
Full case history with a free Klarifi account
Every action against Southern Marin WWTP with dates, milestones, violation types and EPA's complete case summaries, plus inspections and informal actions.
Key contacts
1 verified contact for Southern Marin WWTP, with validated emails and direct phone numbers.
Unlock 1 verified contact
Names, validated emails and direct phone numbers for decision-makers at Southern Marin WWTP, plus the full compliance history and discharge data.
Nearby wastewater treatment plants in California
Tiburon · 4 mi away
0.000000013 MGD
Sausalito · 5 mi away
—
San Francisco · 13 mi away
72.75 MGD
Oakland · 14 mi away
—
Novato · 14 mi away
—
Pinole · 15 mi away
—
Rodeo · 18 mi away
—
Pacifica · 19 mi away
2.59 MGD
Southern Marin WWTP: frequently asked questions
Sources and methodology
Flow, permit and violation figures come from the EPA's ICIS-NPDES discharge monitoring records. Population served comes from the Clean Watersheds Needs Survey 2022. Treatment structures are identified by Klarifi's review of aerial imagery, and capital improvement projects are extracted from published municipal budget documents. Violations are counted over the last three years of monitoring reports.
Data refreshed October 26, 2026; facility record last updated September 13, 2026.
Wastewater terms: POTW · MGD · NPDES permit · Inflow and infiltration · Equalization tank · Centrate · all terms