Cal. Water Code § 13540

(a) A person shall not construct, maintain, or use any waste well extending to or into a subterranean water-bearing stratum that is used or intended to be used as, or is suitable for, a source of water supply for domestic purposes. (b) (1) Notwithstanding subdivision (a), when a regional board finds that water quality considerations do not preclude controlled recharge of the stratum by direct injection, and when the State Department of Public Health, following a public hearing, finds the proposed recharge will not degrade the quality of water in the receiving aquifer as a source of water supply for domestic purposes, recycled water may be injected by a well into the stratum. The State Department of Public Health may make and enforce any regulations pertaining to this subdivision as it deems proper. (2) This section shall not be construed to do either or both of the following: (A) Affect the authority of the state board or regional boards to prescribe and enforce requirements for the discharge. (B) Preempt the exercise by a water district of its existing ordinance authority to impose or implement stricter standards for protecting groundwater quality in the receiving aquifer. (c) If the State Department of Public Health makes the findings provided for in subdivision (b), the department shall consider the state board’s Statement of Policy with Respect to Maintaining High Quality of Waters in California, as set forth in Resolution 68-16, dated October 28, 1968, and shall also consider current and potential future public health consequences of the controlled recharge.