Cal. Civ. Proc. Code § 1240.510

Any person authorized to acquire property for a particular use by eminent domain may exercise the power of eminent domain to acquire for that use property appropriated to public use if the proposed use will not unreasonably interfere with or impair the continuance of the public use as it then exists or may reasonably be expected to exist in the future. Where property is sought to be acquired pursuant to this section, the complaint, and the resolution of necessity if one is required, shall refer specifically to this section.