Upon the final acceptance from the contractor of any specific project on the Chickasaw basin plan, the governing body or bodies of the county or counties wherein the project is physically located may at their option require the authority to relinquish the control and operation of the project to the county; provided, that such county shall thereafter be fully responsible for the cost of maintenance and operation of such project and shall receive all revenues therefrom, except such revenues as might be pledged to the payment of obligations theretofore incurred by the authority.