SD1 (A special enterprise district involving Larkspur, Ross Valley, and San Quentin) has a total of 20 pump stations, 6 being force main stations, and covers over 27 square miles. Since 1981 the District has had a contract with the State of California for wastewater collection at San Quentin Prison. The Larkspur Sanitation Area was annexed to SD1 in 1993, at the request of the City of Larkspur. At the same time SD 1 took over the contract Larkspur had with Murray Park Sewer Maintenance District.