HomeMy WebLinkAboutWPO201400068 Review Comments Stormwater Management Plan 2014-10-06�pF A
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COUNTY OF ALBEMARLE
Department of Community Development
401 McIntire Road, Room 227
Charlottesville, Virginia 22902 -4596
Phone (434) 296 -5832 Fax (434) 972 -4126
Project: Farmington Country Club Southside Improvements -WPO
Plan preparer: WW Associates
Owner or rep.: Farmington Country Club
Plan received date: 11 Aug 2014
Date of comments: 6 Oct 2014
Reviewer: Michelle Roberge
A. WPO (WP02014000068)
1) Show soil map of site.
2) The drainage area A table on sheet C -13 shows a BMP practice to a rain garden #2. The plan does
not show a rain garden. Please clarify if you are proposing a rain garden.
3) The sloped area south of the proposed parking lot all drain to the biofilter, but only .5 acres is
shown going to the bioretention practice. It appears more than .5 acres will drain to biofilter.
Please revise.
4) Add this note on C -12 for biofilter mix. "Tested for acceptable phosphorus index between 10 and
30 or between 7 and 23 mg/kg of P in soil media."
5) Submit perc rate for biofilter area. (One per 1,000 sq ft of filter surface). Also, verify that the
bottom of #57 aggregate is 2' above seasonably high water table.
6) Label underdrain with Schedule 40 PVC with cleanouts. Show 12" depth for #57 aggregate.
7) The geometry of basin does not meet spec of bioretention design criteria. Short circuiting should
be prevented. Please revise.
8) Show the 2' gravel diaphragm level spreader at pretreatment area. On profile view, show the lip on
level spreader.
9) I recommend moving the curb cut location away from the corner of parking lot and shifting layout
of gravel spreader to enter far east side of biofilter.
10) Two rip rap strips are shown on plan, but only one profile view is shown. Please show both since
one is from sidewalk and the other from the culvert under the golf cart path. My concern is that
#57 stones will wash away at steeper slopes. The detail shown is for sheet flows off pavement,
Engineering Review Comments
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then into a pretreatment area that is flat. Please clarify design since the detail has been modified.
11) The water quantity analysis for channel protection should show the actual drainage area to the
point of analysis, such as drainage area A, B, C and existing areas. The CN should be different to
drainage area D. The spreadsheet shows how much phosphorus to remove, but channel analysis
cannot be determined by the separate disturbed drainage areas alone since the CN is not correct.
12) Please clarify the total drainage area to pond. It appears to be larger than what is shown.
13) Clarify the surface elevation of the bioretention area. The profile shows 607, but the plan view
shows 606.
14) Relabel bioretention facility #2 under the Bioretention Facility sizing calculations. It should be
bioretention facility #1.
15) Submit a Pollution Prevention Plan and a Stormwater Pollution Prevention Plan.
Sincerely,
r&vde--
Michelle Roberge