Agenda - 09-05-2000-9b - Laserfiche WebLink

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ORANGE COUNTY PLANNING & L~TSPECTIONS DEPARTMENT P05T OFFICE BOX Sl$1 306-F REVERE ROAD HILLSBOROI7GH, NORTH CAROLINA 2727$ ~~wnt~ a e. d~ '+. u EROSION CONTROL DMSION Carrporo/Chapel Hill 968501 burham 688-7331 Hillsborough 732-81$1 Mebane 227-2031 Telephone Extension 2586 FAX 919-644-3002 Memorandum TO: Craig Benedict, Planning Director FROM: warren Faircloth, Erosion Control Supervisor SVHJECT: Woodlands Subdivision Hydrologic & Hydraulic Engineering Report DATE: August 1, 2000 The report answers questions about the culvert under Nine Gates Road but does not address other questions about increased flow through the Cox property. The illustration in the report demonstrates the benefits of using a 54" culvert instead of the 24" pipe to handle the existing flow without overtopping the road. This is a NC DOT requirement. - The report just states the increase in the rate of runoff from the 8 lots through the Cox property. It does not address the effects, if any, this increase will have on the existing wet soil or on the diversion that conveys runoff in a path different than that shown on the topographic map. (The engineer would not have been aware of this man made diversion unless he went onto the Cox property.) It appears that the increased runoff through the Cox woods and pasture will not will not have significant impact since the flow follows the existing, natural flow path. The path is not developable because of the poor soil and any structures would have to be built outside of the~drainageway. The suggestion has been made to retain the temporary sediment basin as a permanent stormwater detention basin above the Cox property. A basin would have to be properly sized, particularly the outlet, to provide any benefits. Given the large lots, retention of vegetation, limits on impervious surface, and use of grass swales the need for a basin is questionable. If provided, the homeowners association should maintain the basin. a /~57 6-14-00