01/25/2011 Env Bd Packet - Laserfiche WebLink

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DRAFT 01 -19 -2011 The minimum information requirements of the Stormwater Management Plan shall be consistent with the most recent version of the NPDES Permit requirements and include the following information: (a) A Grading, Erosion and Sediment Control Plan and, for projects that require a NPDES permit, a Stormwater Pollution Prevention Plan. (b) Bankfull discharge rate of creek, stream, or river if there is a water course on the site or if the site discharges directly to the water course. (c) Existing and Proposed hydrologic calculations for total runoff volume and peak discharge rates by subwatershed for the 2 -year 24 -hour frequency event, 10 -year 24 -hour frequency event, and 100 -yr 24 -hour frequency event or the 100 -year 10 -day snowmelt. These shall include: 1. Assumed runoff curve numbers. 2. Time of concentration used in calculations. 3. Pre - existing total runoff volume and peak discharge rates. 4. Configuration of all drainage areas. 5. Total amount of new impervious surfaces created by the project. 6. Post - construction total runoff volume and peak discharge rates with no detention. 7. Post - construction total runoff volume and peak discharge rates with detention. (d) Locations of all stormwater management practices, infiltration areas, and areas not to be disturbed during construction. (e) Location of all drain tiles on the project site shall be identified. (f) Location and engineered designs for structural stormwater management practices including stormwater treatment devices that remove oil and floatable material (e.g., basin outlets with submerged inlets). (g) Normal water level, high water level, and emergency overflow elevations for the site and all ponding systems. (h) Layout of proposed streets showing centerline gradients, section widths and typical cross sections. Alternative Format 12 • • •