3322 BROADWAY COMPASS HEALTH 2025-10-03

STORMWATER SITE PLAN COMPASS HEALTH PHASE AUGUST 5, 2022 PAGE 3 0114&111►1010IisL71111I[Q►&**11IT, I►71/_1:V1 DESCRIPTION The project is located to the west of Broadway between 33rd and 34t" and east of the alley, see Figure 1: Vicinity Map. It is part of the larger Compass Health properties in the area. The site currently contains a large behavioral health service building with supporting parking and infrastructure. The balance of the site is impervious with some planter areas. All fronting streets are fully developed with Broadway having parallel parking, curb and gutter and a sidewalk; and 33rd Street having angled parking, curb and gutter, and a sidewalk; and 341" Street having parallel parking, curb & gutter, a planter strip and sidewalk. The alley way is fully paved. Topography drops from the alley to Broadway ranging from 10-12 percent along 33rd and 341n There is no natural topography left and the building has been cut deeply into the original grade. See Figure 2: Existing Site Map. SOILS DESCRIPTION Geotech Consultants, Inc prepared a geotechnical report titled, Geotechnical Engineering Study dated August 31, 2017. They performed 4 test pits and 1 test boring on the Phase 1 site at the corner of Lombard and 33rd. The boring was located in the upper portion of the site and the 4 test pits in the lower area west of the existing buildings. The underlying soils in the east were determined to be topsoil overlying 2 to 5 feet of fill over till. The boring encountered weathered till over the dense till. See geotechnical report in Appendix B. Since the Phase 2 site is adjacent and cut deeply into the native soils, the expected soils encountered will be dense till. EXISTING BASIN The site is located in the Combined Sewer Area of the City of Everett. As such, detention is required if there is 200 sf of added impervious over that of the current site development. In this case, Phase 2 will see a marked reduction in impervious surface (18,800 sf). Therefore, the site does not meet the requirement for a detention system and no basin has been delineated. UPSTREAM ANALYSIS There is no upstream basin. The alley, the curb along 33rd and the curb along 341" block any flow from the west. DOWNSTREAM ANALYSIS Currently runoff either sheetflows to the curb of Broadway or is piped from the site to either the intersection of Broadway and 33rd storm system or the intersection of Broadway and 34tn storm system. Runoff from the alley flows to 33rd in the northern % or 34t" for the southern %. In any direction, the runoff ultimately drains into the combined sewer system. The proposed on -site storm system discharges to the combined sewer system. The City of Everett mapping indicated no basement flooding issue in the local area. [^�crk\Pr e".Ls\i021v,2 -OSG Arkrom mRass He a J L ivDc..S�.,�'ral 7riinaoe Repc-L.dcc