Cal. Pub. Res. Code § 3222

The owner or operator of any well shall, at the request of the supervisor, demonstrate that water from any well is not penetrating oil-bearing or gas-bearing strata or that detrimental substances are not infiltrating into underground or surface water suitable for irrigation or domestic purposes. The owner or operator shall give the district deputy adequate notice of the time at which he will demonstrate the test for shutoff in the well.