(1) A district shall have power to establish, maintain, and operate a mutual water, sewerage, drainage, and street lighting system, a mutual system of any two or three of the systems, or separate systems.
(2) Where any two or more districts include the same territory as of July 1, 1997, none of the overlapping districts may provide any service that was made available by any of the other districts prior to July 1, 1997, within the overlapping territory without the consent by resolution of the board of commissioners of the other district or districts.
(3) A district that was a water district prior to July 1, 1997, that did not operate a system of sewerage or drainage prior to July 1, 1997, may not proceed to exercise the powers to establish, maintain, construct, and operate any system of sewerage or drainage without first obtaining written approval and certification of necessity from the department of ecology and department of health. Any comprehensive plan for a system of sewers or drainages or addition thereto or betterment thereof, proposed by a district that was a water district prior to July 1, 1997, shall be approved by the same county and state officials as were required to approve such plans adopted by a sewer district immediately prior to July 1, 1997, and as subsequently may be required.