(1) The purpose of this subchapter is to establish effluent limitations, treatment standards, and other requirements for point sources discharging wastes into state waters. These requirements, together with the rules in subchapters 13 and 14, are adopted to discharge the responsibilities of the board and department under Title 75, chapter 5, parts 3 and 4, Montana Code Annotated, the Montana Water Quality Act, to adopt effluent standards and treatment requirements and to require compliance with such standards in permits issued to point sources discharging into state waters. These requirements are adopted in a manner the national pollutant discharge elimination system (NPDES) established and administered for the EPA under the federal Clean Water Act.