HomeMy WebLinkAboutWPO200700038 Review Comments Stormwater Management Plan 2009-02-25ALg�,��
1'IRGINZ�
COUNTY OF ALBEMARLE
Department of Community Development
401 McIntire Road
Charlottesville, Virginia 22902 -4596
Phone (434) 296 -5832 Fax (434) 972 -4126
Project: WPO- 2007 - 00038, Pollak Vineyards SWM Plan Amendment
Plan preparer: Alan Franklin, Terra Concepts, PC (fax 434.295.2103)
Owner or rep.: Darmar Farms LLC (fax unknown)
Date received: 26 January 2009
Date of Comment: 25 February 2009
Engineer: Phil Custer
The SWM plan amendment for Pollak Vineyard, received on 26 January 2009, has been reviewed. The
plan cannot be approved until the following items are addressed:
1. Please provide calculations confirming that the Water Quality Volume has been impounded
behind the check dams. My calculations show that with the current design only 735cf is
ponded. (I have attached an excel spreadsheet that I used for this calculation.) Engineering
review will provide some relief by requiring that the only patio, building, and gravel portions
of the water quality volume (ignoring the phosphorous load from the vineyard) to be treated.
This reduces the WQv from 2832cf to 1440cf. It appears that by increasing the height of the
check dams (up to 18 ") or widening the channel (up to 6ft) this can be achieved.
2. The depth of the soil mixture for the water quality swale must be 30 ". (VSMH)
3. An underdrain pipe in at least 6" of gravel must be provided underneath the biofilter mix. The
only justification for removing the gravel and underdrain pipe would be soil tests showing that
the in -situ soils have a permeability rate of greater than 0.52 in/hr.
4. Please remove "Luckstone Biofilter mix" from detail 13/20.
5. Each check dam must have a centralized low point or weir. The low point or weir must be
sized to pass the ten -year storm within the banks of the swale. (Engineering review will waive
the 6" freeboard requirement specified by the VSMH because of the rural location.) Please
show this in a detail (or existing detail 13/20).
6. Please note the location of each check dam in the profile.
7. Please correct the width (from inches to feet) of the swale in detail 13/20.
8. Detention requirements have been met. However, I do not see anywhere in the VSMH that
attributes a 20% removal rate to a dry detention basin. Please remove any reference to this
from the plan and calculations.
File: El_swm_PBC_07 -038 Pollak Vineyards SWM Amendment.doc