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Element #11: Maintain BMPs <br />Temporary and permanent erosion and sediment control BMPs shall be maintained and repaired <br />as needed to ensure continued performance of their intended function. <br />Element #12: Manage the Project <br />The project disturbs less than an acre of land and a Stormwater Pollution Prevention Plan <br />(SWPPP) is not required. Erosion control BMPs used will be monitored and inspected as needed. <br />Element #13: Protect Low Impact Development BMPs <br />Protect lawn areas from construction equipment. <br />ON -SITE STORMWATER MANAGEMENT <br />This project is a redevelopment project draining to the combined sewer system and is not <br />required to meet the stormwater management standards outlined in the 2019 Stormwater Manual <br />and Section 4 of the DOSS. <br />The project will generate approximately 3,400 square feet of new impervious surfacing and is <br />subject to meet the requirements of DCSS 6-10. 1, which includes matching peak runoff rates for <br />the 25- and 100-year storm events between the existing and developed conditions (see <br />Appendix B for stormwater calculations). <br />The following proposed On -site Stormwater Management BMPs will be used on the project. <br />1. Gravel Trench Dmin: Stormwater from the proposed pedestrian plaza will be collected in <br />a gravel trench to detain and release stornwater downstream. <br />a. Trench is 3 feet wide by 2 feet deep along the perimeter of the plaza area. <br />b. Outlet pipe has a 1-inch diameter orifice plate to meet discharge rate <br />requirements. <br />2. BMP T5.12 — Sheet Flow Dispersion: Stonnwater from the proposed pedestrian <br />walkway will disperse into the adjacent vegetation. <br />a. Ten feet of vegetative dispersion area is available for the sidewalk area. <br />BMP T5.13 — Post -Construction Soil Quality and Depth: All proposed landscape areas <br />will use imported topsoil mix to meet the requirements of this BMP. <br />CONVEYANCE <br />The new storm pipe will be sized to convey the 25-year recurrence interval peak flow from the <br />tributary site area. The Rational method was used to develop runoff flows from the site. <br />Manning's equation was used for preliminary pipe sizing. Appendix B provides sizing <br />calculations. <br />Stormwater Site Plan 8 ti® <br />Index Lawn Project <br />