6201 ASSOCIATED BLVD BASE FILE 2018-03-29

� U lam' 0 33 Post-Development Condition In order to achieve the Pre-Mining basin characteristics the entire 200,0000 square foot building rooftop area within Phase 1 & 30% within Phase 2 will flow into CEMEX's site and be incorporated into the zero discharge on-site stormwater management plan. Eventually this area will be tributary to Pigeon Creek when development of the remainder of the CEMEX property is complete. New pollution generating impervious surfacing in the proposed development will be pre-treated prior to entering the wetpond by a Vortechs pre-treatment vault. Runoff will then enter a water • quality wetpond prior to connection into the Glenwood regional facility. The water quality wetpond treating all new pollution generating impervious surfacing will provide up to 85%of the required storage area in a deep (3-6') treatment cell. The remaining required dead storage will be contained within a 15%water quality treatment cell with an average cell depth of 2 feet. The Glenwood regional infiltration / detention facility provides streambank erosion control in accordance with City of Everett requirements in effect at the time of construction. 4.0 OFF-SITE ANALYSIS REPORT This section evaluates the upstream and downstream drainage system. The intent of this section is to identify any existing or potential drainage impacts created or exacerbated by the proposed project and drainage facilities. 4.1 Task 1: Study Area Definition The offsite analysis study area was identified from a USGS contour map and several site visits during 2010. • 4.2 Task 2:Review of Available Information • The following resources were utilized in preparation of this section: AeroMetric Topographic&Existing Feature Map Snohomish County SnoScape Landscape Imaging Interactive Map National Resources Conservation Service Web Soil Survey 2.2 4.3 Task 3: Field Inspection Several field inspections were performed in 2010 to verify downstream conditions. Stormwater discharges from the Glenwood regional facility on the north side of Merrill Creek Parkway and flows unimpeded beyond 1/4 mile from the site. No sign of significant erosion or backwater • effects were noted. Review of the Snohomish, County Snohomish County Landscape Imaging, SNOSCAPE, website, indicates Glenwood Creek is categorized as Non Fish habitat. DAVID EvANs AND ASSOCIATES,INC. UNDERWOOD GARTLAND EVERETT FEBRUARY 3,2015 STORMWATER SITE PLAN PAGE 4