Cal. Food & Agric. Code § 33513

Human excreta or other human wastes shall be properly disposed of by the use of flush toilets and septic tanks, approved pits, or chemical toilets. Such toilets shall be conveniently located and properly constructed, operated, and maintained, so that the waste is inaccessible to flies and does not pollute the surface soil or contaminate any water supply. No approved pit or chemical toilet, however, shall be permitted within 100 feet of the milk house or room or within 50 feet of any milking barn, stanchions, or other place where milking is done.