For purposes of this chapter, the following definitions are applicable:

(1) "Ecology" shall mean the Washington state department of ecology.

(2) "Approval and a certification of necessity" shall mean an order of ecology which gives approval to a water district to establish, maintain, construct and operate a sewer system in a proposed service area in accordance with RCW 57.08.065.

(3) "Necessity" shall mean a reasonable need and not mean an indispensable need.

(4) "Proposed service area" shall mean the area proposed to be served with a sewer system by the applicant water district.

(5) "Sewer system" shall mean a system of sewers and appurtenances for the collection, transportation, treatment and disposal of sewage and industrial wastes.

(6) "Sewage" shall mean the water-carried waste products or discharge from human beings or other wastes from residences, public or private buildings, or industrial plants, together with such ground, surface or stormwaters as may be present.

(7) "Industrial wastes" shall mean the liquids, solids, or other wastes resulting from any process of industry, or from the development of any natural resource.

(8) "Drainage basin" shall mean a geographic area drained by a surface stream or body of impounded water together with all tributary surface streams and bodies of impounded surface water.

(9) "Sewer entities" shall mean any municipal or public corporations which by law are entitled to construct and operate a sewer system.