Pub. Contract Code, § 9203

(a) Payment on any contract with a local agency for the creation, construction, alteration, repair, or improvement of any public structure, building, road, or other improvement, of any kind which will exceed in cost a total of five thousand dollars ($5,000), shall be made as the legislative body prescribes upon estimates approved by the legislative body, but progress payments shall not be made in excess of 95 percent of the percentage of actual work completed plus a like percentage of the value of material delivered on the ground or stored subject to, or under the control of, the local agency, and unused. The local agency shall withhold not less than 5 percent of the contract price until final completion and acceptance of the project. However, at any time after 50 percent of the work has been completed, if the legislative body finds that satisfactory progress is being made, it may make any of the remaining progress payments in full for actual work completed.

(b) Notwithstanding the dollar limit specified in subdivision (a), a county water authority shall be subject to a twenty-five thousand dollar ($25,000) limit for purposes of subdivision (a).