Government Code § 55085
ARTICLE 4. Agreements for the Joint Construction and Maintenance of Sanitation Facilities
When by resolution a legislative body determines and declares that it is for the interest or advantage of the local agency to become a party to the amended or supplemental joint agreement, it may provide for the joint payment of the costs, and joint use, benefit, and maintenance, of the outfall sewers and conduits upon the terms and under the regulations approved by the legislative bodies of all the local agencies entering into the amended or supplemental agreement.