3214 BROADWAY BROADWAY KINECT APARTMENTS 2021-08-11

• • • SECTION 2: SITE ASSESSMENT • Topography: • The site slopes to the east and ranges between 4 and 11 percent. Prior to being cleared the project site contained • miscellaneous buildings, parking lots,and gravel areas.Currently the site is cleared with dirt and gravel throughout • the site. • Drainage: • Drainage from the site flows to the east and is intercepted by Broadway and flows into catch basins and inlets in • Broadway Ave.Stormwater from the alley flows north into 32"d St.where it flows east into catch basins located on • 32"d St.and Broadway Ave. • Soils: . Per the geotechnical report provided by Earth Solutions NW, LLC,the site contains soils described as silty sand with • gravel (SM)with quaternary till deposits throughout. Groundwater was not encountered. See Appendix 5 for the • geotechnical report. • Ground Cover: • The project site was recently cleared within the past couple years. Prior to clearing,the north portion of the site • was an asphalt parking lot,there were gravel areas south of the parking area.The project site also contained a house,a garage,and other miscellaneous small buildings with associated parking. 111 • Critical Areas: • No critical areas have been identified for the project from the City of Everett GIS data. • Adjacent Areas: • To the north of the site,across 32"d Street is an apartment building. To the west of the site across the alley are • residences and a church. To the south of the site is a couple of businesses, and further to the south,another • apartment building. To the East of the site across Broadway Ave are offices. No adjacent areas will be affected • during and after construction,all stormwater will be detained on-site.Stormwater flows from the alley,and along 32"d St.and Broadway Ave. will not be affected. • SECTION 3: SITE DEVELOPMENT PLAN W/ON-SITE STORMWATER MANAGEMENT • The house,garage, building and parking areas have been demolished and removed. The proposed apartment • building will cover the entire site. A stormwater vault will be placed within the parking garage with access through a vault door. The vault has been sized to mitigate the stormwater flowing from the site. MGS Flood was used to size the vault using the conditions prior to the project site being cleared. Flow discharge requirements state,flow • control may be provided by limiting the peak developed rate of runoff from the 2-year,24-hour design storm to 50 • percent of the existing condition 2-year, 24-hour design storm while maintaining the existing condition peak runoff . rate for the 10-year,24-hour and 100-year,24-hour design storms. Stormwater will be conveyed from the roof of the apartment building through roof drain pipes down into the vault located in the northwest corner of the lower level of the parking garage.The vault dimensions are 28.5 feet long, 40 11 feet wide,and from the floor to the ceiling.The flow control structure contains two orifices with an emergency • overflow at elevation 83.35,created approximately 3 feet of freeboard.The bottom elevation of the live storage of • the vault will be 78.12,the vault with have 6"of sediment storage in the bottom.The 50-year water elevation will be 83.35.The stormwater will gravity flow from the flow control structure into an 8" pipe at 1.5%, until it meets • • Broadway Apartments 6 of 9 Stormwater Site Plan • •