All moneys of the district applicable to the payment of improvement costs shall be placed in a fund designated “construction fund,” the moneys in which shall be disbursed by the treasurer of the district as ordered by the board of directors. This fund may be used to pay all improvement costs, all necessary engineering, legal and other operating costs of the district, including salaries of officers, agents and employees, and for the payment of the cost of the purchase and acquisition of all necessary property and rights of way required for any district project.