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HomeMy WebLinkAboutWPO201100043 Review Comments Erosion Control Plan 2012-04-25� OF AL ,. vIRGI1`IZP COUNTY OF ALBEMARLE Department of Community Development 401 McIntire Road Charlottesville, Virginia 22902 -4596 Phone (434) 296 -5832 Fax (434) 972 -4126 Project: Bramley Farm ESC Plan (WPO- 20 1 1 - 00043) Plan preparer: Mr. Alan Franklin, PE; Water Street Studios Owner: Bramley Farm LLC Plan received date: 7 July 2011 (Rev. 1) 18 August 2011 (Rev. 2) 4 April 2012 Date of comments: 14 July 2011 (Rev. 1) 18 October 2011 (Rev. 2) 25 April 2012 Reviewer: John Diez (Rev. 2) Phil Custer The third submittal (Rev. 2) of ESC plan for the Bramley Farm (WPO- 20 1 1 - 00043), received 4 April 2012, has been reviewed. This third submittal has been significantly modified since the last submittal, most notably the removal of a sediment basin. For this reason, new review comments have been provided below. 1. Silt fence appears to be the sole treatment method for the eastern half of the disturbed area. However, the drainage area for 100ft of silt fence is greater than 1/4 acre standard in most cases and the sediment -laden water heading to the eastern level spreader is released unfiltered entirely. Please provide a sediment trap or basin in the place of the eastern level spreader and provide a diversion dike west of this trap. Please also replace the silt fence south of the driveway between the two traps with a diversion dike that will direct runoff to either of the facilities. 2. Please draw the maximum drainage areas to both traps. The design of the sediment traps cannot rely on internal or cleanwater diversions to micromanage the drainage areas because these cannot be realistically maintained on a construction site. For instance, please remove the cleanwater diversion above the barn and redesign of the western facility accordingly. 3. Please provide a diversion dike or permanent channel on the west side the driveway from the construction entrance to the sediment trap to assure that runoff is not released from the site without treatment. 4. Minimum Standard 19 has not been addressed with this application. The only reference to MS -19 is when the narrative states that an adequate channel analysis will need to be provided when Phase I1 is submitted. The current application warrants an analysis downstream channel adequacy according to state parameters. Additionally, when designed properly, level spreaders only meet downstream channel adequacy concerns until the overland flow reconcentrates, which seems to be immediately after the eastern level spreader. Analyses of the channels downstream of level spreaders still need to be provided. Level spreaders do not have a good track record in the county and I would advise against relying on them for even a small percentage of downstream channel concerns. 5. Flow from level spreaders cannot be directed over fill as implied around the western sediment trap. 6. Level spreaders can only be used when there is a slope of less than 10% downstream of the facility. It appears the location of both level spreaders violate this rule. 7. A grading permit cannot be issued for this project until the ESC bond is posted. Bonds will not be Albemarle County Community Development Engineering Review Comments Page 2 of 2 computed until after plan approval. To receive a bond computation, please submit a Bond Estimate Request Form to the County Engineer after the plans have been approved.