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12 <br />Stormwater <br />1) A Stormwater Impact Statement will be prepared for any proposed improvement to the site. <br />The Stormwater Impact Statement will include the following information: <br />a) Written narrative describing existing and proposed conditions, anticipated stormwater <br />impacts and management structures and strategies to mitigate impacts <br />b) Description of land uses and area (in square footage) <br />c) Existing and proposed impervious surface area in square feet for all subareas and project <br />area <br />d) Ground cover and uses information <br />e) Soil information (classification, infiltration rates, depth to groundwater and bedrock) <br />f) Tim of concentration calculations and assumptions <br />g) Topography (2 -foot contours) <br />h) Pertinent on -site and off -site drainage conditions <br />i) Upstream and /or downstream volumes <br />j) Discharges and velocities <br />k) Backwater elevations and effects on existing drainage conveyance facilities <br />1) Location of jurisdictional wetlands and regulatory FEMA Special Flood Hazard Areas <br />m) Water quality volume calculations <br />n) Drainage areas and sub -areas delineated <br />o) Peak discharge calculations and rates (1, 2, and 25 -year storms) <br />p) Hydrographs for pre -and post - development without mitigation, post — development with <br />mitigation <br />q) Volume calculations and documentation of retention for 2 -year storms) <br />r) 85% total suspended solids (TSS) removal for post - development stormwater run -off <br />s) Nutrient loading calculations <br />t) Stormwater best management practice (BMP) sizing calculations <br />u) Pipe sizing calculations and schedule (include hydraulic grade line and energy grade line <br />calculations and profiles) <br />2) A Stormwater Management Plan is required for all new work at the site. The plan will included <br />proposed and existing contours at a 2 foot intervals. All existing drainage conditions, features <br />and stormwater piping and structures shall be shown on the plan. All Resource Conservation <br />District (RCD) areas on the site shall be noted with delineated boundaries. All proposed <br />stormwater systems and drainage conditions must be shown. A piping system for the new <br />stormwater system shall be shown with the associated schedule. New roof drains from all <br />buildings shall be shown to their terminations. All proposed stormwater easements shall be <br />labeled and provide a 20 foot width at a minimum. All proposed best management practices <br />shall be shown on the plan with associated details and sections. New plantings and stabilization <br />techniques shall be noted on this plan. A Stormwater Management Plan will included <br />compliance with the latest Town of Chapel Hill requirements as well as Jordan Lake Rules, and <br />shall be approved prior to issuance of a Zoning Compliance Permit. <br />Lighting /Street and Parking Lots <br />All street and parking lighting plans will be approved by the Town of Chapel Hill Community Design <br />Commission (CDC) prior to issuance of a Zoning Compliance Permit. <br />Southern Orange County Government Services Campus I MASTER PLAN Page 8 <br />