HomeMy WebLinkAboutWPO200800039 Review Comments Stormwater Management Plan 2008-05-28ALg�,��
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COUNTY OF ALBEMARLE
Department of Community Development
401 McIntire Road
Charlottesville, Virginia 22902 -4596
Phone (434) 296 -5832 Fax (434) 972 -4126
Project: WPO- 2008 - 00039, Moser Radiation SWM and ESC plan
Plan preparer: Ammy George, Timmons Group fax 434.295.8317
Owner or rep.: Rectors and Visitors of the University of Virginia fax unknown
Date received: 15 April 2008
Date of Comment: 28 May 2008
Engineer: Phil Custer
The ESC and SWM plans accompanying the major site plan amendment for the Moser Radiation Building,
received on 15 April 2008, have been reviewed. Engineering review can approve the plans once the
following changes are made.
A. ESC Review Comments
1. Please remove the silt fence from the eastern property boundary. The proposed placement will not
filter any runoff in the field.
2. If tree protection fencing is shown, please show it to the standard: limits of clearing line shown
outside of fencing, no grading allowed inside fencing, fencing located around the dripline. Please
also note that the ARB review will be checking the tree protection areas as well and sometimes
their requirements are stricter than the minimum standard in the VESCH.
3. Any reference to the biofilter should be removed from the ESC sheet. The biofilter will be
installed once the site is stabilized to the satisfaction of the on -site ESC inspector.
4. The graded area for the biofilter should be used as a sediment trap during construction of the
building.
5. Please extend the construction entrance to the eastern property line. Please label this area as a
staging area as well. A variance will be given from the required 12'x70' dimensions for a
construction entrance. The construction entrance and staging area should drain into the sediment
trap by way of a defined ditch between the buildings.
6. Please clearly show the ditch between the two buildings to bring runoff north of the building
addition to the sediment trap/biofilter. There is to be no standing water in the Northeast corner of
the site.
7. Please provide an adequate channel analysis of the downstream storm sewer system. [VESCH,
DM]
8. All slopes steeper than 3:1 must have a low maintenance, non -grass groundcover. [DM]
9. Please provide dust control on the plan. [DM]
A. SWM Review Comments
A BMP removal spreadsheet was not received for this development. A total pollutant removal
computation was provided on sheet C2 instead. I have performed a computation for the post -
development drainage area as delineated on sheet C5 and found a required removal rate of 89%
using the County's Modified Simple spreadsheet. Because this required removal rate is
unattainably high for this drainage area, the current policy of engineering review is to accept a
facility with a removal rate of 65 %. No SWM facilities are required for drainage areas in which
impervious areas are not being modified.
2. Please remove the Luckstone mix from the biofilter section detail. Albemarle County currently
accepts only a state - approved mix.
3. Please provide a small forebay on the eastern end of the biofilter where the Swale enters. The
biofilter should be sized in accordance with the VSMH.
4. Stormwater management facilities must have a lft freeboard during the 100 -year storm.
5. The minimum ponding depth for biofilters is 6 ".
6. The 3" pea gravel layer should be included in the 1.5' layer of stone, not in the biofilter mix
section.
7. Please provide a planting plan for the biofilter. The planting plan should be designed using the
guidelines listed in the VSMH.
8. What type of grate will be used on the ADS inlet? This should be called out on the plan because it
affects the detention /routing calculations. Please specify the product number and provide on the
plan its stage- discharge chart that is provided by the manufacturer so detention compliance can be
confirmed.
9. Please submit a signed stormwater maintenance facility agreement and fee to the county with the
next submittal. Any questions regarding this procedure should be directed to Pam Shifflet
(x3246).
10. Please provide a letter from VEPCO stating that the biofilter will be allowed to be placed inside
their easement.
11. Please show the SWM access easement from the entrance aisle onsite rather than from the VDOT
ROW. The existing grades and condition of this area will not require anything other than the
delineation on the site plan.
File: E1 esc swm PBC 08 -039 Moser Radiation