Sewage from homes and businesses in the Mill Valley area is currently piped to the wastewater treatment plant at the end of Sycamore Ave.
In 1900 when Mill Valley became a town, there were septic tanks, out houses and creeks that became open sewers.
An outfall line had been installed down Miller Avenue to collect sewage and discharge it into Arroyo Corte Madera del Presidio.
By 1926, the outfall line had been extended, first to the marsh, then to the estuary and finally to a slough inlet of Richardson Bay.
Mill Valley and bordering communities gradually installed sewer lines to collect and connect to the outfall line.
In 1979, the Sewerage Agency of Southern Marin (SASM) was formed to develop a state of the art wastewater treatment plant. SASM is made up of six Member Agencies: City of Mill Valley, Almonte Sanitary District, Alto Sanitary District, Homestead Valley Sanitary District, Richardson Bay Sanitary District and Tamalpais Community Services District. Sewage flows through several treatment operations that remove a variety of pollutants.
Processed wastewater is disinfected and pumped 6 miles to Raccoon Strait in Tiburon for deep-water discharge into San Francisco Bay.
(For more vignettes on Marin history see the Mill Valley Historical Society website at mvhistory.org or go the Marinscope Community Newspapers website at MarinLocalNews.com.)