Whenever a district has accumulated money in the maintenance fund or general fund of the district in excess of the requirements of that fund, the board of commissioners may in its discretion use any of that surplus money for any of the following purposes: (1) Redemption or servicing of outstanding obligations of the district; (2) maintenance expenses of the district; (3) construction or acquisition of any facilities necessary to carry out the purposes of the district; or (4) any other proper district purpose.