HomeMy WebLinkAboutSDP202200029 Correspondence 2022-06-27ipROUDABUSH, GALE & ASSOC. , Inc.
A PROFESSIONAL CORPORATION Serving Virginia Since i956
June 24, 2022
Ben Holt, Senior Planner
Albemarle County Community Development
401 McIntire Road
North Wing
Charlottesville, VA 22902
RE: SDP202200029 S.L. Williamson Asphalt Plant (at Red Hill Quarry) — Final Site Plan
Dear Mr. Holt,
have reviewed your comment letter dated May 27, 2022. 1 am offering my responses to the
individual comments below in red.
Albemarle County Planning Services
1. [32.6.2.A] —General info. Include conditions of approval for SP2019-09.
The conditions of approval for SP2019-09 have been added to the Cover Sheet.
2. [32.6.2.A] —General info. Update Critical Slopes note from under review to approved.
The critical slopes note has been updated to state that it has been approved.
Albemarle County Engineering Division
1. Sheet 4:
Provide existing spot shot elevations to delineate /establish there is an existing berm
along west edge of (S.L. Williamson) lease area not precisely reflected by existing
topographic contours. FSP does not indicate proposed change to berm along west edge
of lease area. Without such grade change, existing topography will direct site storm
runoff to proposed settling basins, which then in turn may (on rare occasion) fill to the
point that detained volume crests proposed settling basin rim (please provide spot elev.
for each proposed settling basin to establish low point of rim, sheet 8), at which point,
given existing topography, Engineering anticipates shallow flooding of the asphalt plant
could occur (as it may at present) prior to breaching overall perimeter lease area berm.
This is important: existing perimeter grade prevents storm runoff reaching a stream to
the west without first passing through a settling basin. The manner of settling basin
pass -through is via shallow flooding with detained basin volume first breaching existing
settling basin rim, and then (which may occur infrequently, or perhaps never during a
10-yr storm event) ponded elevation may rise until such point detained runoff may crest
lease area perimeter elevation. During site visit 4/15/22, Engineering observed no trace
or pattern of detained storm runoff escaping lease area. Rather, ponded runoff level
does not appear to exceed existing settling basin capacity. Drawdown of existing
settling basin ponded volume appears to occur via infiltration to earth, or evaporation.
Ref. email to Applicant (J. Anderson to Planning Div. coordinator /RGA: April 19, 2022
4:27 PM; ISP/FSP review comments, SDP202100092) for additional information. The
999 Second Street SE. Charlottesville. VA 22902. www.Roudabush.com 434.977.0205
SL Williamson Final Site Plan SDP2022-29
6/24/2022
purpose of discussing settling basin elevations in detail is to affirm Engineering
understanding of design, which is: site storm runoff will in fact reach one of two
proposed settling basins depicted on sheet 8 prior to reaching the stream to the west
(unnamed tributary to North Fork Hardware River). Also, item 2.a., below (from
4/19/22 Engineering review comment email).
Grading Detail sheets have been added to the plan set to show that show that the
existing berm will be re -shaped during the construction of the project. The berm is still
in place near Settling Basin #1 to prevent any water leaving the site prior to entering the
basin.
b. Remainder of Engineering review comments for SDP202200029 mirror text sent as April
19, 2022 4:27 PM email; specifically:
2. "C7 [Now Sheet 8/Grading Plan with SDP202200029]
a. Provide spot elevations that indicate all site storm runoff reaches proposed settling
basins, and that establishes relative grade as close as possible to existing vertical
interval between rims of existing settling basins and perimeter site grade before slope
falls steeply to the creek.
The Grading Detail sheets show the rim elevations of the basins and shows how the
runoff will pass through plant to the settling basins.
b. With WPO plan:
i. Provide mitigation plan (with proposed plantings) for proposed improvements
within landward 50' of stream buffer.
The stream buffer mitigation plan is provided in the WPO plan as Sheets 11 and 12.
ii. Compare (via table) existing volume and proposed volume of settling basins. Total
proposed settling basin volume should equal to or exceed total existing settling
basin volume.
The table to compare the volumes of the existing and proposed settling basins is
provided on Sheet 7 of the WPO Plan.
iii. Recommend submit WPO plan /application at earliest convenience.
Ackowledged.
iv. Note: site visit 15-Apr by county engineering indicates volume of existing settling
basins, existing basin rim elev., inlet design, site perimeter elevation, and circulation
patterns appear to provide adequate storm runoff management for routine
operations at the plant, and as discussed /outlined in correspondence with RGA
(email, Friday, April 15, 2022 1:03 PM), design that mimics current basin volume, rim
elevation/s, and site perimeter elevation are goals that may alleviate nearly entirely
storm runoff concerns relative to adjacent stream water quality.
3. An approved WPO plan (ESC, SWIM, Mitigation) is required prior to FSP approval.
Acknowledged.
4. Settling basins are not SWM facilities, but rather serve industrial site runoff settling
/filtering function. Water evaporates from basins. Ex. settling basins have no outlet.
999 Second Street SE. Charlottesville. VA 22902. www.Roudabush.com Page 2 of 3
SL Williamson Final Site Plan SDP2022-29
6/24/2022
Engineering anticipates similar design with WPO plan: details that provide basin volume,
profiles, with no outlet."'
Basin details and comparison are on Sheet 7 of the WPO plan along with the profiles of the
existing and proposed basins. Basins have been designed to catch all water from the site.
Sincerely,
AvutvvuU c,eorge, PLA
999 Second Street SE. Charlottesville. VA 22902. www.Roudabush.com Page 3 of 3