HomeMy WebLinkAboutWPO201900021 Correspondence 2019-06-21TIMMONS GROUP
YOUR VISION ACHIEVED THROUGH OURS.
June 12, 2019
John Anderson
County of Albemarle
401 McIntire Rd Rm, 227
Charlottesville, VA 22902
608 Preston Avenue P 434.295.5624
Suite 200 F 434.295.8317
Charlottesville, VA 22903 www.timmons.com
RE: UVA Research Park Loop Road — VSMP Permit Plan Review — WP02019-00021- Comment
Response Letter
Dear Mr. Anderson:
We have reviewed all of your comments from May 8, 2019 and made the necessary revisions.
Please find our responses to the comments below in bold lettering.
A. Stormwater Pollution Prevention Plan (SWPPP)
The SWPPP content requirements can be found in County Code Section 17-405. A
SWPPP must contain (1) a PPP, (2) an ESCP, (3) a SWMP, and (4) any TMDL measures
necessary.
a. Sec. 1 (Registration Statement): Revise to include:
I. An email address for Todd Marshall, UVA Foundation.
An email address for Todd Marshall had been added.
II. Registration Statement signature.
Acknowledged, A signature will be provided once a contractor has been
selected.
b. Sec.9 (Signed Certification): Please sign.
Acknowledged, A signature will be provided once a contractor has been selected.
c. Sec.11 (General Permit Copy) Please include 2014 VAR10.
The above is now included in the SWPPP
d. List WP02019-00021 on cover of SWPPP.
The WPO number is now included on the cover of the SWPPP
CIVIL ENGINEERING I ENVIRONMENTAL I SURVEYING I GIs I LANDSCAPE ARCHITECTURE I CONSTRUCTION SERVICES
The PPP content requirements can be found in County Code section 17-404.
1. If Sec. 6 PPP Exhibit is revised, please provide an updated Exhibit.
The PPP has been updated with the revised layout.
C. Stormwater Management Plan (SWMP)
VSMP Regulation 9VAC25-870-108 requires the VSMP authority to approve or
disapprove a SWMP. This plan is disapproved for reasons listed, below. The stormwater
management plan content requirements can be found in County Code Section 17-403.
1. Revise plan title to include ref. to VSMP / WP020190021.
The plan title has been revised to call out the WPO Number
2. VSMP Plan and Road Plan Design Calculations & Narrative, 3/25/19:
a. SWM Quantity Narrative — Include information highlighting (via prior -approved
graphic, narrative, zoning, site, or WPO data) how eastern side of project drains
to a large wet pond that was designed to handle Stormwater quantity for the full
build out of the research park. Recommend information identical to Timmons
Group Lewis and Clark Drive Road Extension VSMP Plan and Road Plan Design
Calculations & Narrative booklet, d. 3/25/2019, pg. 18-19.
Drainage exhibits have been added to calc book.
b. LD-229: Provide computational data requested at D.ESC Plan, items 7 and 8.
LD-299 has been updated. See revised calc book
c. Revise SWM routings — see items 14, 15 below.
SWM routings have been revised to match current drainage areas and CN
values.
3. Ensure dry pond design details on VSMP/WPO match details on SUB201900049, or
preferably limit design detail provided for dry pond on the Road Plan to conceptual
outline, saving details for the VSMP / WPO Plan.
Acknowledged plan is developed as one set with select sheets included in the road or
VSMP plan as necessary.
4. Show proposed SWM Facility / Access / Drainage Easements.
Easements have been added to plan See sheet C4.0.
5. Provide curb break / mountable curb to provide SWM Facility Access (ACDSM, pg.12).
Provide access label or note on plan and linework with proposed grading that meets
ACDSM standard, text image, below, for dry pond Access:
Best Management Practices for Stormwater Management: All practices must have
adequate vehicle access; 10' width graded at less than 20%. Anything over 20% must be
surfaced with gravel or pavement. Access must be to all structures and forebay cleanout
areas. Easements must be provided over all access and facilities, to accompany deeds
and agreements as available on the county website;
20' wide segment of CG-7 mountable curb, 10' wide vehicle access road with 20%
maximum slope, and easement lines have been added.
6. Provide typ. Detail, transition from CG-6 to mountable (rolltop) curb at point of SWM
facility access.
Detail has been added to sheet C1.1
7. Recommended ref. SUB201900049, UVA Research Park Loop Road (Road Plan), on C0.0.
Reference has been added to sheet C0.0
8. Sheet C1.1 is not strictly necessary. Recommend remove this sheet from the VSMP /
WPO Plan.
Acknowledged. Sheet has been removed.
9. C1.2: Provide VDOT IS-1 detail (inlet shaping).
Detail has been added to sheet C1.1
10. C4.2, C4.3 are not strictly necessary. Recommend remove these sheets from the VSMP /
WPO Plan.
Acknowledged. Sheets have been removed.
11. C5.3 is not strictly necessary. Recommend remove this sheet from the VSMP/WPO Plan.
Acknowledged
12. C6.1/Stormwater Quality: VSMP Plan and Road Plan Design Calculations and Narrative
(booklet) 3/25/19 submitted with SUB201900049 does not appear to include runoff
reduction spreadsheet (VaRRm.xls); apparently no booklet submitted with
WPO201900021. Provide VARRm.xls. (Only booklet re. to Water Quality in booklet,
image below pg.3).
VRRM pages have been added to the calc book and digital version of VRRM has been
provided.
Water Quality:
The current site is undeveloped. 4.66 acres of disturbed area was analyzed for water
quality. There will be 1.08 Ibs/year to be treated via manufactured treatment device.
The remaining 0.22 Ibs./yr of required nutrient credits area to be purchased from a
DEQ-Approved Nutrient Credit Bank in Accordance with CA code 62.1-44.15:35.
Acknowledged
13. Note: Applicant must coordinate nutrient credit purchase with Ana Kilmer, Albemarle
County, once plan review comments are addressed prior to purchasing credits. Purchase
of nutrient credits is required for VSMP plan approval.
Design has been revised so that offsite credit purchase is no longer necessary.
14. C6.1: A fair portion of the 3.10 Ac. Off -site post -development area cannot reach the dry
pond without inlet west of N-S leg of loop road similar to inlet south of E-W section of
the loop road. See images, below (blue outlined area). Please provide inlet / pipe
connection to route this off -site runoff to the dry pond, to qualify for quantity
compliance as well as to collect flow at an otherwise low -point that lacks drainage
outfall, unless runoff is to sheet over the curb onto the paved surface.
The area indicated sheet flows over the curb or across the edge of pavement and flows to the
gutter and inlet.
C5.1: offsite routed low point without collection — blue circle/highlight (contour 576'+-)
Offsite runoff will sheet flow over curb into inlet 114
15. Ensure plan CN/Acreage match routing report values. Sub -catchment 3S, 9S report
values do not match plan data. Revise routings, consistent with plan sheet C6.1/ref.
images:
The CN values and acreage have been updated on sheet C6.1 to match the routing report.
16. L1.0: VDOT Std Class Al riprap dimensions need not appear on this sheet.
The dimensions no longer appear on this sheet.
17. L1.0: Recommend shift leader line of label reading 'Tie to nearest inlet (Typ.)' to more
clearly indicate UD-4 (Typ) is to tie to nearest inlet.
This leader line has been removed from this sheet.
18. Choose BMP practice from approved list, or an approved proprietary measure.
a. Use plan labels that identify/match a best management practice listed at 2011
Design Specifications for Practices 1-15.
Labels added to sheet C5.0 calling out Stormtech Isolator Row (Practice 17, filtering
device) and Baysaver Barracuda (Practice 16, hydrodynamic device).
b. If design proposes an Extended Detention (ED) Pond, use link to visit the
Clearinghouse and carefully consider design criteria listed at VA DEQ Stormwater
Design Specification No. 15, Section 6, including:
i. 6.1- Overall sizing
ii. 6.2 —Treatment Volume Drawdown and Detention Design
iii. 6.3
— Required Geotechnical Testing
iv. 6.4
— Forebay Design
v. 6.5
— Conveyance and Overflow
vi. 6.6
— Internal Design Features
vii. 6.7
— Landscaping and Planting Plan
viii. 6.8-
Maintenance Reduction Features
ix. 6.9
— ED Pond Material Specifications
Extended Detention is not proposed as part of this project. A dry pond
will be used to control stormwater quantity, but it will not be
considered a BMP for stormwater quality
c. Provide detailed plan and profile for a listed practice that meets design criteria.
Details have been added to sheets C6.2 and C6.3
d. Provide Landscaping and Planting Plan. Example of partially approved Ex. Det.
Pond profile / recent VSMP / WPO Plan submittal (photo, below):
Landscape plan was included in previous submission; however Extended Detention is
not proposed as part of this project. The pond is a dry pond for quantity only.
19. Additional SWM Plan (VSMP / WPO) review comments possible, once plan re-
submitted.
Acknowledged
D. Erosion and Sediment Control Plan (ESCP)
Virginia Code 62.1-44.15:55 requires the VESCP authority to approve or disapprove an
ESCP. This plan is disapproved for reasons listed, below. The erosion control plan content
requirements can be found in County Code Section 17-402.
1. C3.1: Provide Paved Wash Rack detail (ACDSM, pg. 8).
A Paved wash rack details has been added to the plan sheet. See sheet C3.1.
C3.2:
2. Show break in SSF at stone weir outfall, ST2.
Break in SSF has been added
3. Label ST1, ST2 stone weir dimensions (L x W) in plan view.
Weir dimensions have been added to weir labels
4. C3.3: Provide Str. # consistent with C3.0 Phase II Sequence.
Numbers have been added to pipe 401 and structure 402, as called out in Phase II Sequence
5. Cannot locate temporary 15" HDPE pipe. Edit/revise C3.0 Phase I sequence, as needed.
Temporary 15" HDPE is located near Construction Entrance. Labels have been modified to
clarify temporary nature of pipe
6. C3.3: Check C3.0 Phase II sequence Note 2.1 against C5.0. Revise if pipe / str. Ref. should
be Str. 300, 301.
Structure 402 and pipe 401 are correct. Note 2.1 on C3.0 has been revised to clarify that storm
system associated with dry pond must be operation prior to removal of temporary HDPE pipe,
which allows offsite runoff to bypass project site during construction
2.1.: Once the contributing drainage area to sediment trap #1 has been permanently stabilized
and approved by the ESC Inspector, remove sediment trap #1. Contractor to ensure silt fence
along the toe of slope is installed and in good condition at all times to ensure existing wetlands
are protected. Once the storm system associated with dry detention basin is operational,
remove the temporary 15" HDPE pipe and end section. Install structure 402 and pipe 401
accordingly.
7. LD-229 submitted with SUB201900049 does not appear to include design computations
for pipe 301. Evaluate design flow and discharge velocity against pipe capacity and
riprap outfall dimensions.
Pipe 301 is routed as part of the Hydrocad analysis for the dry pond.
8. Evaluate discharge velocity against riprap outfall, Str. 200 / VDOT ES (capacity appears
sufficient).
Riprap calculations have been added to calc book
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,
Jonathan Showalter, PE
Project Engineer