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Eastern Washington Phase H Municipal Slorinii afer Permit When Core Element #5 Runoff Treatment is required, Core Element #7 Operation and Maintenance also is required. Basic Treatment Basic runoff treatment (to remove solids) is required for all new development projects creating 5,000 square feet or more of pollutant -generating impervious surface (PGIS) areas. Treatment is required for discharges to all surface waters of the state, including perennial and seasonal streams, lakes and wetlands where the PGIS threshold is met. Runoff treatment is also required for discharges of stormwater to ground where the vadose zone does not provide adequate treatment capacity (see Chapter 5.6 the Stormwater Management Manual for Eastern Washington (2004), or another technical stormwater manual approved by the Department). Basic runoff treatment is required for redevelopment projects creating 5,000 square feet or more of PGIS where: • The project takes place at an industrial site as defined by EPA (40 CFR 122.26(b)(14)) with outdoor handling, processing, storage, or transfer of solid raw materials or finished products, or • The project takes place at a commercial site with outdoor storage or transfer of solid raw materials or treated wood products, or • A need for additional stormwater control measures has been identified through a TMDL or other water cleanup plan or other planning process, or • The project takes place at a high -use site, or • The project takes place in an area subject to vehicular traffic under any of the following conditions: o The project improves a soft shoulder to a curb and gutter roadway with projected average daily traffic (ADT) of 7,500 or more vehicles. o The project replaces and/or improves the surface of a parking area where the projected number of trip ends exceeds 40 per 1,000 square feet of building area or 100 total trip ends per day. o The project replaces and/or improves the surface of an urban road where the projected ADT is 7,500 or more vehicles per day. o The project replaces and/or improves the surface of a freeway or rural road where the projected ADT is 15,000 or more vehicles per day. o The project affects the area within 500 feet of a controlled intersection on a limited access control highway with projected ADT of 7,500 or more vehicles per day. Only this area must be treated. Exceptions: Non -pollutant generating impervious surface (NPGIS) areas are exempt from basic treatment requirements unless the runoff from these areas is not separated from the runoff Appendix 1- Minimum Technical Requirements Eastern Washington Phase II Municipal Stormwater Permit —August I, 2014 Page 11