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1 <br /> T <br /> a <br /> 3.3 Post-Development Condition <br /> In order to achieve the Pre-Mining basin characteristics the entire 200,0000 square foot building <br /> rooftop area within Phase 1 & 30% within Phase 2 will flow into CEMEX's site and be <br /> incorporated into the zero discharge on-site stormwater management plan. Eventually this area <br /> will be tributary to Pigeon Creek when development of the remainder of the CEMEX property is <br /> complete. <br /> New pollution generating impervious surfacing in the proposed development will be pre-treated <br /> prior to entering the wetpond by a Vortechs pre-treatment vault. Runoff will then enter a water <br /> quality wetpond prior to connection into the Glenwood regional facility. The water quality <br /> wetpond treating all new pollution generating impervious surfacing will provide up to 85% of the <br /> required storage area in a deep (3-6') treatment cell. The remaining required dead storage will <br /> be contained within a 15%water quality treatment cell with an average cell depth of 2 feet. <br /> The Glenwood regional infiltration / detention facility provides streambank erosion control in <br /> accordance with City of Everett requirements in effect at the time of construction. <br /> 4.0 OFF-SITE ANALYSIS REPORT <br /> This section evaluates the upstream and downstream drainage system. The intent of this section <br /> is to identify any existing or potential drainage impacts created or exacerbated by the proposed <br /> project and drainage facilities. <br /> 4.1 Task l: Study Area Definition <br /> The offsite analysis study area was identified from a USGS contour map and several site visits <br /> during 2010. <br /> 4.2 Task 2: Review of Available Information <br /> The following resources were utilized in preparation of this section: <br /> AeroMetric Topographic & Existing Feature Map <br /> Snohomish County SnoScape Landscape Imaging Interactive Map <br /> National Resources Conservation Service Web Soil Survey 2.2 <br /> 4.3 Task 3: Field Inspection <br /> Several field inspections were performed in 2010 to verify downstream conditions. Stormwater <br /> discharges from the Glenwood regional facility on the north side of Merrill Creek Parkway and <br /> flows unimpeded beyond 1/4 mile from the site. No sign of significant erosion or backwater <br /> effects were noted. <br /> Review of the Snohomish, County Snohomish County Landscape Imaging, SNOSCAPE, <br /> website, indicates Glenwood Creek is categorized as Non Fish habitat. <br /> DAVID EVANS AND ASSOCIATES,INC. <br /> UNDERWOOD GARTLAND EVERETT FEBRUARY 3,2015 <br /> STORMWATER SITE PLAN PAGE 4 <br />