Notwithstanding any of the provisions of Chapter 31, article 5, the board of trustees of any sanitary district heretofore or hereafter organized under any of such sections which includes within its boundary or partially within its boundary a natural resources district, shall have full power without further authorization to contract with such natural resources district, for said sanitary district to discontinue all its activities, including the operation of any and all drainage systems located within or serving such sanitary district and including the right to construct sewers lying outside the limits of any corporate city or village, all as is provided for in said Chapter 31, article 5. Said contract may also authorize the transfer of all properties and assets used or useful by said sanitary district, and the assignment of all obligations and liabilities of said sanitary district, to such natural resources district upon such terms and conditions as may be agreed upon between such natural resources district and such sanitary district.