About Us

Wastewater TreatmentGoal

It is the goal of SASM to operate, maintain, and manage the SASM Wastewater Treatment, Reclamation, and Disposal Facilities in an efficient, cost-effective, and well-planned manner in order to protect our water environment.


The Mission of the Sewerage Agency of Southern Marin is to efficiently provide wastewater treatment services to its member agencies and work cooperatively with government agencies on all compliance requirements, guided at all times by the following core values:

  • Public health and safety with an emphasis on facility operations, employee safety, and neighborhood well-being
  • Operational excellence, customer service and public education
  • Environmental stewardship with an emphasis on quality treated effluent, zero controllable spills, and re-use of biosolids, methane and reclaimed water
  • Support and encourage cooperative activities between all member agencies


The Sewerage Agency of Southern Marin (SASM) is a Joint Powers Agency formed in 1979 to consolidate the wastewater collection, treatment, water reclamation and disposal needs of about 29,500 residents in Southern Marin County.

Member Agencies

SASM is made up of six Member Agencies (MAs). They are:

  • The City of Mill Valley
  • Tamalpais Community Services District
  • Almonte Sanitary District
  • Alto Sanitary District
  • Homestead Valley Sanitary District
  • Richardson Bay Sanitary District

Each Sanitary District has one seat on the SASM Board of Commissioners. View a map of SASM's service area.

Each MA owns, operates and maintains a sanitary sewer system. These sewer systems connect to the main sewer lines owned by SASM which carry the wastewater to the wastewater treatment plant.

Wastewater Treatment

At the wastewater treatment plant, the water flows through several treatment units which reduce and remove a variety of pollutants and organic materials. The processed wastewater is disinfected and pumped 6 miles to Racoon Straits in Tiburon for deep water discharge into the San Francisco Bay.

To see how a typical wastewater system functions, please visit Go With the Flow, an informational website provided by the Water Environment Federation.

Processed wastewater is further treated, or reclaimed, and used for landscape irrigation. The City of Mill Valley Parks Department uses reclaimed water throughout Bay Front Park. Use of reclaimed water for landscape irrigation saves precious fresh water supplies for domestic use.

The City of Mill Valley staff at the SASM Wastewater Treatment Plant is dedicated to protecting our water environment by meeting all regulatory requirements while providing the highest level of service and efficiency. For contact information, please visit our Contact Us page.