Cal. Water Code § 13951

Notwithstanding any other provision of law, on or after January 1, 1972, waste from within the Lake Tahoe watershed shall be placed only into a sewer system and treatment facilities sufficient to handle and treat any such waste and transportation facilities sufficient to transport any resultant effluent outside the Lake Tahoe watershed, except that such waste may be placed in a holding tank which is pumped and transported to such treatment and transportation facilities. As used in this section “waste” shall not include solid waste refuse. The further maintenance or use of cesspools, septic tanks, or other means of waste disposal in the Lake Tahoe watershed on or after January 1, 1972, by any person, except as permitted pursuant to this section, is a public nuisance. The occupancy of any building from which waste is discharged in violation of this section is a public nuisance, and an action may be brought to enjoin any person from occupying any such building. This section shall not be applicable to a particular area of the Lake Tahoe watershed whenever the regional board for the Lahontan region finds that the continued operation of septic tanks, cesspools, or other means of waste disposal in such area will not, individually or collectively, directly or indirectly, affect the quality of the waters of Lake Tahoe and that the sewering of such area would have a damaging effect upon the environment. This section shall not be applicable to any area or areas within the Fallen Leaf Lake watershed in the event the regional board for the Lahontan region finds that with the export of toilet wastes by single-family residences or with the export of toilet and kitchen wastes with respect to any commercial properties, the continued use of septic tanks, cesspools, or other means of waste disposal in such area or areas for the treatment and disposal of the remaining wastes, will not, individually or collectively, directly or indirectly, affect the quality of the waters of Lake Tahoe, and that the sewering of such area or areas would have a damaging effect upon the environment. This section shall not affect the applicability of Section 13950.