Cal. Pub. Util. Code § 1501
The Legislature recognizes the substantial obligation undertaken by a privately owned public utility which is franchised under the Constitution or by a certificate of public convenience and necessity to provide water service in that the utility must provide facilities to meet the present and prospective needs of those in its service area who may request service. At the same time, the rates that may be charged for water service by a regulated utility are fixed by the Public Utilities Commission at levels which assume that the facilities so installed will remain used and useful in the operation of the utility for a period of time measured by the physical life of such facilities.
The Legislature finds and declares that the potential loss of value of such facilities which may result from the construction and operation by a political subdivision of similar or duplicating facilities in the service area of such a private utility often deters such private utility from obtaining a certificate or extending its facilities to provide in many areas a water supply essential to the health and safety of the citizens thereof.
The Legislature further finds and declares that it is necessary for the public health, safety, and welfare that privately owned public utilities regulated by the state be compensated for damages that they may suffer by reason of political subdivisions extending their facilities into the service areas of such privately owned public utilities.
Ca. Pub. Util. Code § 1501