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t t <br /> 0 <br /> 3.0 Developed Site Conditions <br /> A clubhouse and clubhouse parking area for the Grandview Apartment complex is proposed to <br /> be built where the playground and storage building once were.A total of 10,900 square feet of <br /> non-pollution generating impervious surface will be added upon completion of the <br /> improvements. <br /> Stormwater runoff from the parking lot will sheet flow west and into a drainage swale located <br /> along the proposed sidewalk west of the parking area. Stormwater within the swale will flow <br /> north towards the clubhouse building and shall be captured within a 12-inch area drain with an <br /> atrium grate. The wall drain for the proposed lock-block wall on the east side of the parking lot <br /> will also drain to this point via 4"PVC pipe. Stormwater collected within the area drain shall be <br /> conveyed west to rain garden which shall be placed along the east side of the clubhouse building. <br /> Stormwater runoff from the clubhouse roof shall also be conveyed to the rain garden from the <br /> roof downspouts. <br /> The proposed rain garden shall provide 6 inches of ponding depth with a 6"underdrain installed <br /> at a minimum of 2.5' beneath the rain garden media. In the event that the 6"ponding depth is <br /> exceeded, stormwater will flow into a Type 1-L catch basin with a beehive grate which will be <br /> placed in the rain garden.Upon over-saturation of the rain garden soil media, excess stormwater <br /> will flow into the 6"perforated pipe and to the Type 1-1 catch basin intended for rain garden <br /> overflow. Stormwater collected within the catch basin will flow north via 6"PVC pipe and into <br /> the combined sewer conveyance system located on site.As this system is being routed to a <br /> combined sewer system,the Type 1-L catch basin located within the rain garden shall be <br /> equipped with a floatable material separator and gas trap. Please see the stormwater plan and <br /> details and sheets C3 and C4 of the attached improvement plans. Rain garden sizing was <br /> determined using WWHM. Refer to the Appendix for the WWHM results. <br /> Rain Garden Design: <br /> Bottom Length: 32.5-ft <br /> Bottom Width: 3-ft <br /> Side Slope: 3H:1V <br /> Ponding Depth: 6" <br /> Freeboard: 6" <br /> Underdrain: 6"perforated PVC pipe <br /> Riser: Type 1-L CB with beehive grate, floatable material separator, and gas trap <br /> Top Rain Garden Elev= 110.0' <br /> Riser Elev= 109.5' <br /> Underdrain Invert Elevation= 106.0' <br /> DAVID EVANS AND ASSOCIATES,INC. <br /> GRANDVIEW APARTMENTS CLUBHOUSE MARCH,2017 <br /> STORMWATER SITE PLAN PAGE 6 <br />