Central Marin Sanitation Agency is a joint powers agency or JPA formed by its member agencies, which are special districts and municipalities in the San Rafael and Ross Valley areas of central Marin County, California. CMSA was formed for the purpose of constructing and operating a wastewater treatment plant located in San Rafael.

The publicly owned and operated treatment plant has a yearly budget of about $8 million a year and treats an average of about 11 million gallons of wastewater a day. Flows contributed by our service area are approximately 8 million gallons per day in dry weather. Rain-induced flows can range over 115 million gallons per day.

Our staff consists of certified wastewater operators, maintenance specialists, laboratory technicians, and engineers whose mission is to safeguard the public health of Marin County residents and protect the environment.