HomeMy WebLinkAboutWPO201800078 Correspondence 2020-04-02TIMMONS GROUP
March 31, 2020
John Anderson
County of Albemarle
401 McIntire Rd, Rm. 227
Charlottesville, VA 22902
608 Preston Avenue P 434.295.5624
Suite 200 F 434.295.1800
Charlottesville, VA 22903 www.timmons.com
RE: Keswick Hall Spa — VSMP Permit Plan Review — WP0201800078 - Comment Response
Letter
Dear Mr. Anderson:
We have reviewed all of your comments from January 15, 2020 and made the necessary
revisions. Please find our responses to the comments below in bold lettering.
C0.0:
1. In text box/lower left, ref. 5/21/19 purchase of 1.09 lb. phosphorus nutrient credits,
which, combined on -site BMPs met WP02018-00078 phosphorus load reduction
requirement of 1.65 lb. Amendment 1 total phosphorus load reduction reduces the
initial 1.65 lb. requirements to 1.28 lb. A surplus, 0.36 lb./yr. (on -site BMPs provide 0.55
lb.) is available to Keswick Hall for future development. A note is recommended as CDD
has no reliable means to track on -site phosphorus credits that accrue from Amendment
1. CDD urges Applicant to rely on credits purchased, and Amendment BMP design; these
combined exceed 9VAC25-870-65 requirements and yield a 0.36 lb. surplus.
Note: Amendment (on -site) BMP provides 0.55 reduction. Initial on -site BMP design
provided 0.56 lb./yr., which, combined with 1.09 lb./yr. purchase, met 9VAC25-870-65
requirements.
On Sheet C0.0, information has been provided under the site information in regards too the
nutrient credits. See section titled "Stormwater Nutrient Credits".
2. Revise Plan title (line 2) to: WPO Plan Amendment 1.
Plan titled has been revised
3. Ensure C3.0 project description LOD (2.60 Ac.) and plan labels are consistent (during
1/15 meeting, discussed possible revision to LOD).
The LOD has been revised to capture additional area of work (2.65 AC).
ENGINEERING I DESIGN I TECHNOLOGY
4. Note: Initial ESC Plan bond amount is based on 2.67 Ac. LOD, 1 sediment trap (2.10 Ac.
DA), 340 LF of diversion dike. Amendment 1 ESC plan requires 2 STs (2.82 Ac. DA = $
expense), and 1,280' +/- diversion dike ($5,170 increase). Current ESC plan bond incl.
$3,987.95 (10% contingency), sufficient to meet required (Amendment) ESC plan bond
amount (C3.1).
Acknowledged. Bonds to remain in place if they are sufficient.
5. Note: Initial SWM Plan bond is based on 2 detention systems, while Amendment 1
proposes a single, slightly larger DIA and longer detention. Applicant may request a
bond reduction based on difference in installed expense (material / labor + contingency)
between 2 facility and 1 facility designs. A bond inspection request form and revised,
design- and Mfr. — furnished estimate of installed expense of larger /longer single
detention vs. two -system detention would be required in order to process SWM plan
bond reduction request. Likewise, there appears to be a reduction in permeable paver
qty., a bonded SWM line item. Any reduction in permeable pavement materials,
earthwork, or labor is basis for bond reduction request, if inspection request form,
revised qty. estimates are submitted, and bond reduction process followed.
Acknowledged. Bonds to remain in place if they are sufficient.
6. C4.0 —Increase proposed 3' walkway width to 4, min. —see image, below.
Sidewalk width was increased to 4 ft.
7. C5.0 — Relocate structure 100 (24" DIA pipe outfall) to a point not more than 50' stream -
ward of the WPO buffer. Ref. 17-604.A. (storm line within landward 50' of WPO buffer is
permissible) Also image, below.
The stormwater outfall has been relocated per SDP comments.
C6.0:
8. Please confirm Flood Protection post -developed Q2, Q10 CFS values are consistent,
wherever they appear (apparent typos during plan review on 01/15).
Sheet C6.0 has been updated to fix typos.
9. Beneath Water Quality Analysis text box, lower -left, please provide initial
WPO201800078 post -developed impervious area, managed turf, and initial total load
reduction required, = 1.65 lb.
Additional information has been added to reflect the original stormwater quality calculations
for reference. See Sheet C6.0.
10. C6.1— Ensure table below is legible once plan is printed.
Font size has been increased accordingly. See Sheet C6.1.
11. C6.2 — Str. 120 allowable ponding depth, 0.4', appears to exceed height of curb opening,
0.333'. Review / revise Str. 120 DI length, as needed.
Calculations have been revised accordingly.
12. C6.6 — Recommended revise SWM facility easement plat, since easement for SW4 is not
needed (SW4 eliminated) and trim SW3 easement dimensions so future improvements
may be built outside recorded easement. Without easement plat revision, SWM facility
easements appear excessive and may conflict with easement. Without easement plat
revision, SWM facility easements appear excessive and may conflict with future
development in proximity to revised building footprint.
Timmons Group is currently working to amend the previously recorded easement plat. Plat
submission to follow soon.
13. Provide sheet similar to L3.30, Mitigation Planting Plan. Ensure proposed mitigation
meets required 2:1 ratio offset required of buffer impact, which may be less than initial
WPO201800078 WPO buffer impact.
Sheet L3.30 has been updated and added back to the plan set.
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 434.295.5624.
Sincerely,
Andrew Allison
Project Engineer