5900 36TH AVE W PRE APP 015 - 032 - SOUNDVIEW BUSINESS CAMPUS - VERITAS Drainage Report 2025-04-22

SOUNDVIEW TECHNOLOGY CENTER EVERETT, WA EXISTING CONDITIONS The Soundview Technology Center project is located at 5900 3611 Avenue West in Everett, Washington. It is identified as parcel #28040300200100. The total site area is approximately 39.45 acres and is currently undeveloped, forested land. The property is zoned Industrial (M-1). The site is generally rectangular and is bordered to the west by undeveloped, forested land in the City of Mukilteo, to the north by residential of Mukilteo, to the east by residential of Everett, and to the south by undeveloped forest land in the City of Everett. The topography of the site is hilly, sloping to the northwest corner of the site. Elevations range from 282 feet to 442 feet. There are four primary drainage basins which drain this site. These basins are shown in Exhibit B and labeled from west to east as Basin A, B, C and D, respectively. Basin A is bordered by a steep slope called Japanese Gulch. The remainder of the site generally drains to the north into two separate sub -basins, which converge approximately 1/4-mile downstream. Basin B discharges to the northwest and into a 12- inch culvert under Debrelon Lane. Basin C discharges to the northeast and into Edgewater Creek. Basin D is comprised of a small depression, south of Basin C, of approximately 1.70 acres which is a wetland in the southeast corner of the site. The wetland area drains into the drainage system within 36th Ave NE and ultimately outfalls into Edgewater Creek less than of a mile downstream. No development or drainage facilities currently exist on the subject site. The project site does appear to have upstream area tributary to the developed region. A portion of the area to the South of the site is tributary to basin A and D. Refer to the Existing Conditions Exhibit in Appendix A for a map of the existing conditions. SOILS CONDITIONS The USGS and soils report titled "Subsurface Exploration, Geologic Hazards, and Geotechnical Engineering Report" for Soundview Technology Center prepared by Associated Earth Sciences, dated June 22, 2016, defines the site soils as Alderwood — Everett Gravelly Loam with a hydraulic soil group C. DEVELOPED CONDITIONS The proposed development will consist of 4, 2-story buildings totaling approximately 461,800± SF with approximately 686 parking stalls, stormwater management facilities, utilities and on -site landscaping on a 39.45-acre site at 5900 36th Avenue West in Everett, Washington. The total developed site will be approximately 25.82 acres. The property is zoned M-1 (Industrial). On -site stormwater runoff that lands on roof surfaces of Building A, B, C, and D, will be collected by downspouts or roof drains and routed to on -site detention #1, #2, #4, and #5, respectively. Storm chamber system #1 will be discharged into Basin D at the east end of the site. Vault #2 will discharge into Basin A at the western portion of the site. Vault #3 & #5 will be discharged into Basin B at the northwest corner of the site. Vault #4 will discharge into Basin C at the northeast portion of the site. Stormwater runoff from roof surfaces will not be treated for water quality. All detention systems are located below parking areas. Stormwater runoff in the upper pavement area surrounding Building A & B plus a portion of Building A will be collected and routed to Vault #4. Runoff collected in Vault #4 will be treated with a Modular Wetland before discharging into Basin C at the northeast corner of the site. Stormwater runoff in the lower pavement area surrounding Building C and D will be collected and routed to Vault #3. Runoff collected in Vault #3 will be treated using a Modular Wetland before discharging into Basin B at the northwest corner of the site. Refer to the Developed Conditions Exhibit in Appendix A for a map of the proposed conditions. MAY 23, 2017 STORMWATER DRAINAGE REPORT PAGE 8 1