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SAGE HOMES NORTHWEST, LLC <br />HARBORS EDGE DRAINAGE REPORT <br />AUGUST 2022 <br />7. OTHER PERMITS <br />Building Permits for each of the buildings will be required. <br />8. CONSTRUCTION STORMWATER POLLUTION PREVENTION PLAN <br />A formal stormwater pollution prevention plan (SWPPP) report will be submitted separately from this <br />report with the construction drawings; however, the discussion below is intended to provide a summary <br />of how the thirteen required SWPPP elements are intended to be addressed. <br />8.1 ELEMENT 1- PRESERVE VEGETATION/MARK CLEARING LIMITS <br />The project will identify the intended clearing limits and mark them in the field with high -visibility <br />construction fencing or silt -fencing. Critical areas and buffers will also be clearly identified in the field, <br />and the project will retain and stockpile the duff -layer and replace it on the completed site to the <br />greatest practical extent. <br />8.2 ELEMENT 2 - ESTABLISH CONSTRUCTION ACCESS <br />A rock -stabilized construction access will be provided at the entrance to the site. Sediment that is <br />tracked off site shall be swept at the end of each day, or as determined necessary by the project's <br />erosion/sediment control lead <br />8.3 ELEMENT 3 - CONTROL FLOW RATES <br />The permanent detention facility will also be used as a temporary sediment trap with the sediment <br />removed after the site is stabilized. <br />A temporary sediment trap will be installed for use during the vault construction. The calculation for <br />the minimum surface area (SA) of the sediment trap is shown below: <br />Sediment Trap <br />SA = 2080Q22 <br />SA=2080*0.39 <br />SA = 811.2 square feet <br />8.4 ELEMENT 4 -INSTALL SEDIMENT CONTROLS <br />Sediment control is expected to be provided via a temporary sedimentation pond on the north side of <br />the property near where the detention facility will be. A series of interceptor trenches will be <br />proposed to route site runoff to this facility. Perimeter silt -fencing will also be installed on the <br />downhill portions of the site. <br />8.5 ELEMENT 5 - STABILIZE SOILS <br />Exposed soils which are expected to remain unworked for an extended period will be stabilized with <br />mulch, seed, or other measures. Soil stockpiles are expected to be covered with plastic or other <br />sediment -trapping measures. <br />PACE l PAGE 20 <br />