HomeMy WebLinkAboutWPO202100007 Correspondence 2021-10-15® COLLINS ENGINEERING
October 15, 2021
Emily Cox, P.E.
Department of Community Development
401 McIntire Road
Charlottesville, VA 22902
RE: Brookhill Blocks 16-17 VSMP Plan (WPO 20210007)
200 GARRETT ST, SUITE K CHARLOTTESVILLE VA 22902
�434.293.3719 PH 434.293.2813 Fx
www.collins-engineering.com
Thank you for your comments sent on August 27, 2021 on the above referenced project. Below are our detailed responses to your
comments. Should you have any questions during your review and approval of this project, feel free to contact Graham Murray at
¢rahamC&collins-eneineerine.com or at (434) 566-3011.
A. Stormwater Pollution Prevention Plan (SWPPP)
2. The overall coverage map exhibit has been updated to include all permit numbers, project numbers, and acreages
3. The registration statement has been updated to be a modification without acreage increase.
B. Pollution Prevention Plan (PPP)
I nip-111—__
C. Stormwater Management Plan (SWMP)
1. This comment is acknowledged and the SWM agreement will be executed prior to plan approval.
2. FDP 20210009 is under review. The applicant will notify the County Engineer once it is approved.
13. In an October 7'h Microsoft Teams meeting between Mr. Murray and County Engineering Staff it was determined that
subareas A and B needed to meet energy balance threshold flows, even if the low -flow orifices were less than 3". As a
result, the plans and calculations have been updated to meet energy balance requirements and now propose orifice
diameters less than 3" for dry detention basins A and B. Additionally, during the October 7'h meeting County Engineering
Staff recommended dry detention basin A's stub pipe have a headwall, metal plate with a cut-out for the low -flow orifice
and a larger trashrack. Sheet 16B and 19B have been updated to accommodate this revision and meet minim State and
County requirements. And lastly, when the low -flow orifice was redesigned for stormwater management system 'B'the
system was reevaluated. Because temporary sediment basin 'B' is being constructed behind the cul-de-sac and lots for
erosion protection, the applicant decided it made the most sense to convert this to a permanent dry detention basin. This
update is reflected in the plans and calculations, and dry detention basin B's riser also includes a metal plate with a cut-out
for the low -flow orifice, a large trashrack and other features intended to reduce the risk of clogging such as a depressed
stone pit below the low -flow orifice.
20. Following the issuance of the comment letter on August 27'h, Mr. Murray provided Ms. Cox with an approval letter from
ADS on August 30v'via e-mail. Ms. Cox then responded on September P stating the ADS approval was sufficient to
address this comment. Additionally, the applicant has included with this submission a re -approval of the Contech
underground detention system 'B', which corresponds to the updated design submitted for approval.
21. Sheet 16B has been revised to include the requested two cross sections. Please note, with the introduction of these two
new cross sections, and the details for the new trashracks and headwall described above in comment 13's response, the
applicant ran out of room on the sheets and was required to add sheet 19B to the set.
D. Erosion and Sediment Control Plan (ESCP)
12. The applicant has submitted documents to Vincent Pero for his approval. The applicant will notify the County Engineer
once it is approved.
Sincerely,
Graham Murray, PE