HomeMy WebLinkAboutSDP201200069 Review Comments Final Site Plan and Comps. 2012-12-19A77
vIRGIN�A
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: Albemarle County Public Safety Training Facility - Final
Plan preparer: Brian McPeters [fax 804 - 673 -3980]
Owner or rep.: County of Albemarle Office of Facilities Development [fax 972-4091]
Plan received date: 12/12/12
Date of comments: 12/17/2012
Reviewer: Michelle Roberge
A. Final Site Development Plan (SDP201200069)
1. VDOT approval is required. Comments will be forwarded when received. [DM905]
2. A 3:1 slope is a preferred slope over the proposed 2.5:1 for areas surrounding the fire range. If a 3:1
cannot be achieved, a soil stabilization of blanket/matting is recommended. The 5' berms in between
the firing ranges are ok, but I recommend 10' wide berms around the site (Per Table 3.01 -1, Minimum
Standard of Virginia SMP).
3. It appears there are two wetlands delineated on sheet CG -100. One wetland is located about 70' west
of the proposed firing range. The other wetland, which will be disturbed, is located east of the firing
range. Per Sec. 17 -317, please provide the stream buffers no less than one hundred (100) feet wide on
each side streams and contiguous nontidal wetlands, measured horizontally from the edge of the
nontidal wetlands. Section 17 -321 allows types of disturbance within the buffer. A mitigation plan will
be required if authorization to disturb the wetland is granted.
4. The proposed road is a gravel road with a crown. It is difficult to achieve a permanent crown with a
gravel road. I recommend a using a sealcoat, especially on the section with a 9% grade.
5. The ditch is too close to the edge of the 20' access aisles. I recommend a 4' shoulder along the access
aisles on both sides due to the ditch being V below the edge of gravel road. Gravel is not necessary on
the shoulder, but permanent stabilization will be recommended to help minimize soil erosion and road
washouts.
6. On sheet CG101, it shows grading beyond the landfill limits. DEQ will need to review the plans if the
landfill is disturbed.
7. There is no note regarding the surface cover in between the parking lot (gravel surface) and the firing
range (stone dust). Please specify permanent stabilization. I recommend providing vegetation cover to
reduce lead movement off site.
8. The section "Proposed Drainage Improvements" in the narrative states that the parking lot will drain
into a stormsewer. Please provide on your siteplan. I recommend an inlet on the NW corner of the
parking lot to be piped into the detention basin.
9. It appears that a removal rate calculation was prepared for the extended detention basin. Please provide
the same calculation for all the biofilters. I have attached an example for the project site. Please note
that this is an estimate.
10. The RR% is about 90 %. I recommend changing the extended basin to a bioretention basin. This will
allow you to remove the smaller biofilter and increase the size of the basin. It will be easier to maintain
one bioretention basin than having an additional network of storm sewer. Please note that a WPO
application, fees and plans are required for review and approval prior to final approval [17 -203, 17-
303].
Sincerely,
19&r—
Michelle Roberge
County Engineer
Short Version BMP Computations
Albemarle County Water Protection Ordinance: Modified Simple Method
Plan: Biofilter Pond Water Resources Area: Development Area
Preparer: Date: 19- Dec -12
Project Drainage Area Designation DA# Project Area
L storm pollutant export in pounds, L = [P(Pj)Rv /12 ] [ C(A)2.72 ]
Rv mean runoff coefficient, Rv = 0.05 + 0.009(1)
Pj small storm correction factor, 0.9
1 percent imperviousness
P annual precipitation, 43" in Albemarle
A project area in acres in subject drainage area, A
C pollutant concentration, mg /I or ppm target phosphorus
f factor applied to RR
V required treatment volume in cy, 0.5" over imperv. area = A(1)43560(0.5/12)/27
RR required removal , L(post) - f x L(pre)
%RR removal efficiency, RR100 /L(post)
Impervious Cover Computation (values in feet & square feet)
Item
1 Rv(pre)
I L(pre)
I L(post)
1 RR
I % RR
Area Type
0.23
pre - development
1 23.88
1 13.15
55%
Area
post - development
1 1.37
Area
Roads
Length
Width
01 01
0 0
subtotal
0
Length Width
01 0
0 0
0 0
1
subtotal
0
0
0
0
0
0
0
0
0
Driveways Length
and walks
Width
0
0
no.
0 0
0 01
subtotal
0
0
0
0
Length Width no.
subtotal
0
0
0
0
0
0
0
0
0
1
0
Parking Lots
1
0
2 3
4
0
1 2 3
4
40
29401
1 1 0
Gravel areas Area
Structures
Actively - grazed pasture &
Ards and cultivated turf
Active crop land
4500 x 0.70 =
Area no.
0 01
0 01
0 01
Area
F 01x 0.08 =
Area
0 x0.25=
subtotal
0
0
0
3150
Area
17000
x 0.70 =
E15 00
200000
0
Area no. subtotal
1700 1 1700
0 0 0
1 0
1700
0
Area
11670001x 0.08 =
13360
0
Area
0 x0.25=
0
Other Impervious Areas
0
0
Impervious Cover
1%1
51
I(pre)
Rv(post)
0.51 262.2
New Development (For Development Areas, existing impervious cover <= 20 %)
C
0.70
0.35
0.40
" min. values
f I (pre).
1.00 20%1
1.00 0°/
1 Rv(pre)
I L(pre)
I L(post)
1 RR
I % RR
Area Type
0.23
1 10.73
1 23.88
1 13.15
55%
Development Area
0.06
1 1.37
1 11.94
1 10.58
89%1
Drinking Water Watersheds
0.06
1.57
13.65
12.07
88%
Other Rural Land
Redevelopment (For Development Areas, existing impervious cover > 20 %)
C f I pre * Rv pre
L pre
L(post)
RR % RR
Area Type
0.23
10.73
1 23.88
1 14.22 1 60%1
Development Area
0.06
1.37
1 11.94
1 10.78 90%1
Drinking Water Watersheds
0.06
1 1.57
1 13.65
1 12.31 1 90%1
Other Rural Land
I(post)