1605 SE EVERETT MALL WAY WALMART 2018-01-01 MF Import

Seattle,Washington = r = , ' www.pacland.com T206.522.9510 TURNING VISIONS INTO REALITY E. Storm water Treatment Plan Stormwater treatment is provided for the equivalent area of new pollution generating impervious created for this project. See the Redeveloped Hydrology section above for a detailed breakdown of the proposed site improvements. The step-by-step process in Volume I, Chapter 4 of the Manual was consulted to determine the type of treatment facilities applicable to the equivalent area of treatment proposed for Fthe project. The results of these steps are below: Step 1: Determine the pollutants of concern The receiving water is not listed for pollutants which are expected to be present on the project site. Additionally, in coordination with the City, additional water quality issues or special basin requirements were not identified. Step 2: Determine whether the facility will be City-owned or privately owned The on-site system will be privately owned. Step 3: Determine whether Oil Control facility/device is required The proposed land use, supercenter, is a commercial site with an expected design year average daily traffic county of 50 to 60 vehicles per 1,000 square feet of gross building area. This is less than the 'high-use site' threshold of 100 vehicles per 1,000 square feet of gross building area. Additionally the site does not propose to store petroleum or transfer in excess of 1,500 gallons per year, park, store or maintain 25 or more vehicles over 10 tons, or contain a road intersection. Therefore, Oil Control is not required. Step 4: Determine whether infiltration for pollutant removal is practicable The onsite soils, and the extent of disturbance done to native soils as a result of past development activities, limit the site suitability for infiltration for pollutant removal. Therefore, infiltration for pollutant removal is impracticable. Step 5: Determine whether Phosphorus Control is required There are currently no established phosphorus control requirements specified by Ecology or the United State Environmental Protection Agency in the City of Everett. This determination was confirmed with the City of Everett. Therefore, Phosphorus Control is not required. Step 6: Determine whether Enhanced Treatment is required The new pollution generating impervious surface requires enhanced treatment due to the fact that the site disturbs an acre or more of land and the receiving water (Silver Lake)is fish-bearing. However, this step specifically includes a note about developments with a mix of land use types. The project area requiring enhanced treatment is less than 50% of 111 the overall 8.57 acre threshold discharge area. Therefore, Enhanced Treatment is not required. Step 7: Select a Basic Treatment Facility Everett Mall Plaza Parcel Ill Retail Expansion Stormwater Site Plan Page 22