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ae...<�'�.. =.�3�.,a'.e -.... _ ^2,�Y3.,.�.i.�:kt+..x....�.e.+�;: "c --.r':@x.�",_.`.<.... 2-..�.:_e.�..:.�..i y_.�.� •-, -ia^ '—...t��Wes�'9._..,d..�a.-��z��� <br /> Since critical areas and buffers encumber the majority of the property, impacts are <br /> proposed under the reasonable use provisions. The majority of parking areas and <br /> building will be placed in the non-forested portion of buffer. The Critical Area Study and <br /> Buffer Mitigation Plan propose two types of buffer enhancements. The area with <br /> established deciduous canopy will be inter-planted with conifers trees. Other areas will <br /> be planted with native trees and shrubs. <br /> The proposed drainage pattern will mimic the existing flows. A portion the site between <br /> the office building and wetland, out of the grading limits and enhanced with landscaping <br /> only,will sheet flow to the wetland undisturbed. Storm water from parking lot and <br /> adjacent grass areas will be conveyed to a CDS vault for pre-treatment. Then, combined <br /> with roof runoff, it will be conveyed to a detention vault for detention; through <br /> StormFilters for additional treatment before being released to the stream. Stream bank <br /> will be protected with a riprap to prevent erosion. <br /> Soils: <br /> Per soil report for this project by Earth Consulting Inc, dated March 31, 2008,most of the <br /> site has been filled. Test pits and borings show 2 to 6 inches of top soil underlying by <br /> medium dense silty sand gravel fill. Fill extends to the depth of 12 to 15 feet below <br /> grade. Underlying the fill and top soil, soft to medium stiff peat with wood debris was <br /> encountered to a depth of 25 feet below existing grade. Native glacial till soils were <br /> observed below the peat, which is consistent with soil map for area showing Alderwood <br /> soils. <br /> Site is located in X Zone on FEMA FIRM map, areas determined to be outside 500-year <br /> floodplain. <br /> See Appendix C for Soil Map and 100-year Floodplain Map. <br /> SECTION II-PRELIMINARY CONDITIONS SUMMARY <br /> There is no existing drainage facility other than the existing 48"concrete pipe which <br /> conveys storm drain waters from the wetland underneath of Casino drive right-of-way <br /> downstream. All existing storm water sheet flow to the wetland, except small portion of <br /> the site,which drains to the Casino Road drainage system. Adjacent ROW system <br /> conveys storm through inlets to underground pipe system. <br /> See Appendix D for Pre-developed Drainage Area Map of the area. <br /> Proposed storm drainage system mimics the existing drainage patterns. The buffer <br /> enhancement area will have no changes on the drainage flow peaks, durations, or <br /> directions. Flow will not become concentrated before entering wetland. <br /> 2 <br />