Cal. Government Code § 865

The Legislature hereby finds and declares that: (a) The gradual movement of land, such as in prehistoric slide areas, or as a result of subsidence due to the depletion of underground or subterranean supporting substances, such as minerals, petroleum sources, water, and similar substances, can result in danger to persons or property. Although the movement is gradual and expressed in terms of numbers of inches, feet or meters per day, week or year, at some point the forces that are exerted by the movement will sever underground utilities, such as water, sewer, gas, electricity or telephone services and can cause the destruction of aboveground structures whose foundations become undermined or where support is denied altogether. Unlike an earthquake or rapid rockslide or landslide, these gradual earth movements permit possible intervention to arrest the movement and avoid harm which is posed to persons or property. If there is an adequate manifestation of the problem before actual harm to persons or property, it is possible to make some determinations as to a method of remedial action which can abate the hazard. However, any undertaking to arrest the earth movement may not be successful or may have within it the potential for hastening the movement and the damages resulting from such movement. Regardless of how slight that potential for aggravating the damages, local public entities are unwilling to undertake action to alleviate the hazard if such undertaking may invite potential liability. (b) It is the intent of the Legislature in enacting this chapter to create an incentive for local public entities, upon learning of the particular earth movement which will result in possible damage to substantial areas of property and constitute a threat of injury to persons, to undertake remedial action to abate the earth movement or protect against the danger therefrom without fear of incurring liability as a result of undertaking such action.