7220 RAINIER DR 2018-01-01 MF Import

DOWNS i REAM ANALYSIS Runoff from the site sheet flows into the ditch adjacent to the site. The ditch enters from the scuthwest corner of the site and flow easterly to the intersection of 74"' St. SE and Rainier Drive. At the intersection the ditch tums to the north and continues flowing northerly adjacent to the eastside of the site. Near the northeast corner of the site, the ditch enters a 36-inch concrete pipe and into an underground storm sewer system (see Photo 3). This system, consisting of pipes and catch basins, eventually discharge into Pigeon Creek No. 1. PROPOSED CONDITIONS Develooed Site Descriotion The proposed site includes building 11 townhomes and a parking area with 22 stalls. There are two entrances to the site, one from the north and one from the south. The north entrance can be accessed from Ttereve Drive and the south entrance will connect into Rainier Drive, crossing the south ditch via a 36-inch reinforced concrete culvert. Stormwater Management Requirements This site is categorized as "Redevelopment of 5000 square feet or more" in Table 1- 1.1 on page 1-1-4 (rev8/99) from the Stormwater Manual. The required plans are SSP and tfie required stormwater controls are source control and runoff treatment. fOposad RunoffTr�t� � �� –, �.S ' ^�) �'7^ 3 —3 Runoff from the proposed impervious areas will be routed tdan open treatment cell located on the east side of the site. The t tment cell was designed to treat the 6- mo`h design storm and to convey-th 00-year storm event. It was also designed to meet tfie�City of Everett Stormwater Management Manual guidelines. The Stormshed (formerly Watenvorks) program was used to produce the proposed runoff and the analysis and results can be found in the appendix. EROSION RISK ASSESMENT 8� MITIGATION Slope Average slope from the site is from 0% to 2.0%. Critical Areas There are no critical areas on the site. Ground Movement There are no features on the site to indicate any potential for seismic or landslides events. Proposed Erosion Control BMP's Source control for the proposed developments include filters fabric fence, straw covering, hydroseeding, and or plastic covering. These measures are typical BMP's and will be implemented according to the City of Everett Small Parcel Erosion and Sediment Controi for disturbing less thatn one acre of land. Tubbs 8 Duesenberg Apartments Page 3 Drainage Report