HomeMy WebLinkAboutWPO201800078 Correspondence 2020-11-09608 Preston Avenue P 434.295.5624
Site 200 IF434.295.1800
T I M M O N S GROUP
Charlottesville, VA 22903 www.timmons.com
November 9, 2020
John Anderson
County of Albemarle
401 McIntire Rd, Rm. 227
Charlottesville, VA 22902
RE: Keswick Hall Spa — VSMP Amendment Plan Review— WP0201800078 -Comment
Response Letter
Dear Mr. Anderson:
We have reviewed all of your comments from November 6, 2020 and made the necessary
revisions. Please find our responses to the comments below in bold lettering.
1. C3.2: Label ST stone weir L x W dimensions, ESC Phase 2
The stone weir dimensions have been added accordingly.
2. CJ ST2: Revise total storage required label to read 68.3 CY
Label has been revised accordingly.
3. C6.1 permeable paver labels are somewhat confusing; label states 0 SF upgradient drainage.
Compare with calculations packet, p. 10 (VRRM.xls, Tech Spec 7, impervious cover credit 0.08
AC, or 3,485 SF. It is not apparent which 3,485 SF are contributes to the permeable pavers. Also,
please note that VRMM.xIs indicates downstream practice to be employed is 6.a. bioretention
#1. No downstream practice, other than underground detention, appears in -line with permeable
pavers. Please clarify, reconcile, revise labels and update .XLS as needed.
The total area of permeable pavement is 3,503 SF (1,753 SF + 1,750 SF from C6.1). This equates
to approximately 0.08 AC of surface area. Since upgradient drainage is not impervious area,
the VRMM spreadsheet reflects water quality treatment of stormwater that hits the surface
area of the permeable pavers (contributing drainage area is the same as the paver surface
area — 0.08 AC). The VRMM spreadsheet has been updated to reflect the removal of the
bioretention downstream practice.
4. C7.1, Str. 108: Provide label requiring %2" steel plate in floor of MH structure, since vertical drop
>4'
A callout has been added to C7.1.
ENGINEERING I DESIGN I TECHNOLOGY
5. Please compare C6.0 and C7.1 top of pipe elevations, 60" CMP storage system: 427.00' (detail
C6.0) vs 427.11' (C7.1). 180 LF (2x90') at 0.33 implies 0.3' fall over length of system; anticaipte
STR116A-SWM3 profile top of pipe elev. = 427.30' rather than 427.11'; similarly, pipe inv. Elev. _
422.30' rather than 422.11'. Please check elev./revise as needed.
Profile "STR324-SWM3" has been updated to better reflect the CMP elevations at this
connection point (Top=427.30'). Profile "STR316A-SWM3" has been updated to reflect the
CMP elevations at this connection point (Top = 427.17). Bottom/Top elevations were taken at
0.33% slope from the weir plate north towards pipes 115 and 117 accordingly.
We have included PDF copies of the plans and calculations for your review. If you have any
questions or comments, please feel free to give me a call at 704.941.4097.
Sincerely,
Andrew Allison
Project Engineer