The purpose of this chapter is to establish a state general permit program, applicable to the discharge of pollutants, wastes, and other materials to waters of the state, including discharges to municipal sewerage systems. Permits issued under this chapter are designed to satisfy the requirements for discharge permits under sections 307 and 402(b) of the federal Water Pollution Control Act (33 U.S.C. §1251) and the state law governing water pollution control (chapter 90.48 RCW).