Cal. Health and Safety Code § 4760

The district board may, by agreement with any city or other public agency, take possession of, or acquire by condemnation or in any other manner any sewerage system, or any sewage or refuse disposal or treatment plant, or any combination of the foregoing necessary or convenient to carry out any of the objects of the district, or may acquire by agreement or in any manner the right to use them, and any city or other public agency may enter into such an agreement with a county sanitation district. A compliance with this chapter is sufficient to authorize such an agreement by either a county sanitation district, city, or other public agency entering into such a contract with a county sanitation district. Whenever any sewerage or refuse disposal system, or sewage or refuse disposal or treatment plant so taken possession of or otherwise acquired was built from the proceeds of a bond issue, the district may assume and pay out of its funds the outstanding bonds of the city or public agency according to their terms, and in that case the principal sum remaining unpaid shall be credited to it and deducted from any sum to be paid by it to the city or public agency. Funds may be obtained by the county sanitation districts to pay the principal and interest on the assumed bonds in the manner as is provided for paying the principal and interest on its own bonds.