The medical superintendent shall make triplicate estimates, in minute detail, as approved by the State Department of Developmental Services of such supplies, expenses, buildings, and improvements as are required for the best interests of the hospital, and for the improvement thereof and of the grounds and buildings connected therewith. These estimates shall be submitted to the State Department of Developmental Services which may revise them. The department shall certify that it has carefully examined the estimates, and that the supplies, expenses, buildings, and improvements contained in such estimates, as approved by it, are required for the best interests of the hospital. The department shall thereupon proceed to purchase such supplies, make such expenditures, or conduct such improvements or buildings in accordance with law.