§ 22. Supervision of contracts. The corporation shall provide for field supervision over improvement, maintenance or repair work on the canal system that is done under contract. The corporation shall assign such engineers, inspectors and other engineering employees as may be necessary for control over the execution of the work embraced in the contract. Such corporation shall cause the preparation and approval of the estimates of the work accomplished, materials delivered, or other items embodied in the contract and the certificate of the amount of payment which may be due under the terms of the contract or legal modifications of the same. Upon the completion of any contract the corporation shall cause the preparation and approval of a certificate of acceptance, stating that the work has been well and faithfully performed in accordance with the terms and conditions of the contract and all legal modifications thereof.