2320 RAILWAY AVE INTERWEST CONSTRUCTION INC 2023-06-12

INTERWEST — EVERETT CONTRACTOR'S YARD INTERIM FILL PROJECT Sitts & Hill Engineers, Inc. CONSTRUCTION STORMWA TER POLLUTION PREVENTION PLAN Job Number 17,733 Section 2 — Existing Site Conditions ' Existing site surfaces include gravel, asphalt pavement, natural vegetation, and an area covered with concrete debris. The exact amount of impervious area is difficult to determine due to the spread of compacted gravel surfaces across the site. Based on site observations, it does not appear that stormwater readily infiltrates. The project site may receive some incidental run-on from neighboring properties to the north, east, and south, though the topography of the site and the boundaries it shares ' with these properties are quite flat. The steepest slopes on site are three to four percent. Runoff from the project site is generally directed to the west where it enters a ditch along the adjacent BNSF railway. This ditch conveys water to a City of Everett pump station located northwest of the project site. This pump station directs water to the City of Everett water treatment facility on the north side of the Snohomish River, northeast of the project site. This downstream flow path can be verified from City of Everett GIS mapping (see Figure 2) and the Public Works Director Interim Policy for Stormwater Control in the Combined Sewer Area (see Figure 3). The City treatment facility ultimately discharges to the Snohomish River. See Figure 5 for contours depicting existing site topography. SI1TS & HILL ENGINEERS, INC. 5 TACOMA, WASHINGTON