902 PINE ST NORTH SOUND BEHAVIORAL HEALTH TREATMENT CENTER 2025-11-04

I 3.0 Offsite Analysis 3.1 Task 1 —Define and Map the Study Area The North Sound Behavioral Health Treatment project site is located at 902 Pine Street in Everett, Washington, and is encompassed by a single parcel number(29051700102000) (see Appendix A-1, Site Vicinity Map). The project site contains one single TDA that discharges to a public storm system located in 10th Street. Refer to Appendix A-2 for the Existing Conditions Map and Appendix A-4 for the Downstream Study Map. The existing site contains impervious and pervious areas, including building roof area, parking area, drop-off area, sidewalks, service loading access drive, and landscape area. Catch basins are located in the existing parking lot. The downspouts of the existing building are connected to existing storm drain. Stormwater generated by the TDA flows south to the existing public catch basins in 10th Street, which then discharge to a private detention pipe owned by Snohomish County before discharging back to the public storm system. The public storm system conveys stormwater west and then discharges to the public combined storm/sewer system that flows south through Wiggums Hollow Park. In the Pre-Application Meeting notes by Public Works dated July 17, 2018, the City noted there are no level of service issues downstream. 3.2 Task 2—Resource Review The following resources were reviewed to discover any existing or potential problems in the study area: • Adopted Basin Plans: The project site is located within the Snohomish River Basin, as identified by the Snohomish Basin Protection Plan, dated December 2015 (see Appendix A-5). • Floodplain/Floodway(FEMA) Maps: The project site is determined to be located in Zone X per Flood Insurance Rate Map#53061C0715 F, which is determined to be outside the 500-year(0.02 percent reoccurrence)floodplain (see Appendix A-6). • Critical Area Maps: The project site is not identified as a critical area, as shown on Snohomish County GIS Maps. No critical aquafer recharge and wetland area is located within 1 mile of the project site. No other hazards such as erosion, landside, and seismic I • areas are identified within 1 mile of the project location (see Appendix A-7). Road Drainage Problems: No road drainage problems are known to exist on the site. • Soils Surveys: Soil types at the project site have been assessed by GeoTest Services Inc. and determined to consist of Glacial Till (Qtv) (see Appendix B-1). Per the USDA Soil Map, the soil type in the majority of the project site area is"Alderwood-Urban land complex, 2 to 8 percent slopes" (see Appendix A-8). In the Geologic and Geotechnical Investigation Report dated November 5, 1996, the site soil was arsenic contaminated and has been required to be cleaned up to Method A soil cleanup level by Department of Ecology(DOE). • Migrating River Studies: No rivers are located within 1 mile downstream of the project site. • Section 303d List of Polluted Waters: No polluted waters are located within 1 mile downstream of the project site per the DOE Clean Water Act Section 303(d) list of polluted water and published maps (see Appendix A-9). I Stormwater Site Plan Report North Sound Behavioral Health Treatment OMOGI AHBL No.2170857.10