The construction of all or any part of the San Joaquin Pumping System may be deferred until such time as the department determines that the construction of it is required and is economically justified.

In case the construction of all or any part of the San Joaquin Pumping System is deferred, the construction of all other units of the project shall be commenced and carried to completion without reference to the construction so deferred.

The department shall ascertain and determine when the project or any unit thereof is completed and thereupon the project or unit shall be deemed completed for all purposes of this part.