Mailing Address:
Alto Sanitary District
PO Box 163
Mill Valley, CA 94942

*Please note that the District does NOT have a physical office. In-person inquiries about the District may be directed to the SASM treatment plant staff at:

Sewerage Agency of Southern Marin
450 Sycamore Avenue, Mill Valley, CA 94941

District Manager (Part-Time Administrator)

Bill Hansell
Tel: (415) 388-3696