General Wastewater Discharge Permit

General permits are wastewater discharge permits that are developed for a category of discharger instead of an individual facility. General permits may be issued under federal (actually combined NPDES/state) or state‐only authority. The Waste Discharge General Permit Program rule, Chapter 173‐226 WAC, clarifies the intent in its purpose statement: “Permits issued under this chapter are designed to satisfy the requirements for discharge permits under 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).” General permits are typically issued for five years. Facilities which are eligible for coverage under the permit apply for coverage and then are covered for the remaining length of the permit. Permittees must reapply for permit coverage at least 180 days before expiration.

Wastewater Flow Rate

Because the hydraulic design of both collection and treatment facilities is affected by variations in wastewater flow rates, the flow rate characteristics have to be analyzed carefully from existing records. In cases where only flow rate data in the collection system is available, it must be recognized that the flow rates may differ somewhat from the flow rate entering the treatment plant because the flow.

Quality Assurance

Very low detection and quantification limits must be achieved to reduce analytical variation and the number of samples below the analytical detection limits. To help reduce sample variation, QA procedures during sample collection and analysis should include careful attention to the major elements identified by U.S. Environmental Protection Agency (USEPA 1995a), including special cleaning procedures for sample containers and filter units, grab sample collection directly into pre‐cleaned sample containers, field filtration with laboratory‐cleaned filter units, field and laboratory blanks, standard reference materials, and field and laboratory duplicate samples. QA procedures and results should be documented in individual project plans and reports for any study.