HomeMy WebLinkAboutWPO201900021 Correspondence 2019-08-30TIMMONS GROUP
YOUR VISION ACHIEVED THROUGH OURS.
August 27, 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 August 9, 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.
Rev.1 Addressed.
II. Registration Statement signature.
Acknowledged, A signature will be provided once a contractor has been
selected.
Rev.1 Acknowledged. Acceptable to Engineering.
b. Sec.9 (Signed Certification): Please sign.
Acknowledged, A signature will be provided once a contractor has been selected.
Rev.1 Acknowledged. Acceptable to Engineering.
c. Sec.11 (General Permit Copy) Please include 2014 VAR10.
The above is now included in the SWPPP
Rev.1 Partially addressed. As follow-up; please replace 23-pg. 2014 General VPDES Permit
with 2019 General VPDES Permit.
The SWPPP has been updated with the updated 2019 General VPDES Permit.
CIVIL ENGINEERING I ENVIRONMENTAL I SURVEYING I GIs I LANDSCAPE ARCHITECTURE I CONSTRUCTION SERVICES
d. List WP02019-00021 on cover of SWPPP.
The WPO number is now included on the cover of the SWPPP
Rev.1 Addressed.
e. New: Sec. 7, Enhanced inspection frequency change with 2019 General VPDES
Permit. Please ref. II G.2.a (pg.13/PDF-ref.link, above). Revise Sec.7, SWPPP.
Section 7 has been revised to reflect the changes in the updated General VPDES Permit.
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.
Rev.1 Partially addressed. As follow-up; Include rectangle labeled concrete washout for
dedicated concrete truck washout (differs from mortar mixing station).
An area dedicated for concrete truck washout has been included.
2. New: Indicate rain gauge location ('x' or rectangle or similar). Label rain gauge.
A rain gauge location has been called out.
3. New: Recommend revise construction entrance label/legend to ref. paved
construction entrance (PCE).
The construction entrance label has been revised accordingly.
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
Rev.1 Addressed.
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.
Rev.1 Addressed.
b. LD-229: Provide computational data requested at D.ESC Plan, items 7 and 8.
LD-299 has been updated. See revised calc book
Rev.1 Addressed.
c. Revise SWM routings — see items 14, 15 below.
SWM routings have been revised to match current drainage areas and CN
values.
Rev.1 Addressed. Also, items 14,15, below.
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.
Rev.1 Partially addressed. As follow-up; See item 18.d., below.
See response for comment 18.
4. Show proposed SWM Facility / Access / Drainage Easements.
Easements have been added to plan See sheet C4.0.
Rev.1 Partially addressed. As follow-up; Revise '10' wide grass access road' label to
'SWM Facility Access.' Outline SWM Facility easement/s. (Please show/label SWM
Facility Access on SUB201900106 — UVA Research Park Loop Road Final Plat.)
Easements have been revised as requested.
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.
Rev.1 Addressed.
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
Rev.1 Not addressed. Sheet C1.1 is not included in the plan, and C1.1 is not listed in
C0.0 sheet list table. Please restore typ. Detail from C1.1 to plans.
Sheet C1.1 has now been included in the VSMP Plan submission.
7. Recommended ref. SUB201900049, UVA Research Park Loop Road (Road Plan), on C0.0.
Reference has been added to sheet C0.0
Rev.1 Addressed.
8. Sheet C1.1 is not strictly necessary. Recommend remove this sheet from the VSMP /
WPO Plan.
Acknowledged. Sheet has been removed.
Rev.1 Addressed. Also, see item 6., above. (Typ. Detail).
9. C1.2: Provide VDOT IS-1 detail (inlet shaping).
Detail has been added to sheet C1.1
Rev.1 Not addressed. Ref. items 6./8.; restore detail to plans.
Detail Sheet C1.1 has been included with the VSMP Plans.
10. C4.2, C4.3 are not strictly necessary. Recommend remove these sheets from the VSMP /
WPO Plan.
Acknowledged. Sheets have been removed.
Rev.1 Addressed.
11. C5.3 is not strictly necessary. Recommend remove this sheet from the VSMP/WPO Plan.
Acknowledged
Rev.1 Addressed.
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.
Rev.1 Partially addressed. The only VaRRM.xls data included with Calc. booklet is
Drainage Area 'A', which appears three times: twice with DA total acreage of 2.10 Ac.,
once with DA total acreage of 2.80 Ac. Please review / revise calculation booklet to
include VaRRM.xIs site, water quality compliance, runoff volume and CN, and summary
tab information, and as many discrete drainage area tabs as there are DAs routing to a
BMP practice. It may be DA 'A' appears multiple times to reflect routing to practices 16
and 17, but all three DA 'A' tab data appear to relate to the filtering device.
The VaRRM Spreadsheet has been revised, and areas have been revised to match
accordingly. Site Tab has been included to show 2.1 Acres the total post developed
disturbed area that does not flow to Preexisting SWM Pond 1. Tab A has been
included to show the treatment achieved by the Barracuda and Isolator Row in Series.
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.
Rev.1 Partially addressed. This is not immediately apparent. See item 12, above. Include
VaRRM.xIs data with calculation booklet, or VaRRM.xIs data clearly presented on plans so that
site and summary data depict phosphorus load reduction required, and practices which reduce
phosphorus to the point that offsite credit purchase is not required. Please do not send
VaRRM.xIs to reviewer to address this comment, since email or e-attachments are not approved
with a VSMP/WPO plan. Engineering, however, appreciates digital VaRRM.xIs submittals. Please
confirm if .xIs sent via email, and if so, date sent.
Offsite credits will be purchased. Credit availability letter has been included with submission.
Digital version of VaRRM spread sheet was emailed to John Anderson 8/27/2019.
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.
Rev.1 Withdrawn. Review of development plans for areas west will likely accommodate
drainage needs at this location. Applicant responses (acceptable in interim). (inlet 114)
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.
Rev.1 Addressed.
16. L1.0: VDOT Std Class Al riprap dimensions need not appear on this sheet.
The dimensions no longer appear on this sheet.
Rev.1 Addressed. Sheet L1.0 removed from WPO plan set.
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.
Rev.1 Addressed. L1.0 removed from WPO Plan set.
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).
Rev.1 Partially addressed. As follow-up: Please provide design plan / profile for Str.
102 (flow-splitter) — see example; photos, below. Include elevations.
A detail of the flow splitting manhole has been provided. Additional details are also
included for the Baysaver and Barracuda 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.
Rev.1 Partially addressed. As follow-up: A SWM quantity measure requires design plan
/ profile detail and calculations comparable to a SWM quality facility. Provide plan
/profile, design and calculations that demonstrate design intent, consistent with
HydroCAD routings. Profile information, in particular, is essential for construction,
inspection, bond estimates, and As -Built comparison with design. C6.0 / C7.0 plan and
riser details are insufficient. Label pond floor dimensions.
Dry pond profile has been added on C7.0. Pond floor dimension have been added to
sheet C5.0.
19. Additional SWM Plan (VSMP / WPO) review comments possible, once plan re-
submitted.
Rev.1 Acknowledged
20. New: Provide additional legible terrain contour labels west of Loop Road.
Additional terrain contours have been included.
21. New: Compare C3.3 pipe layout, which appears to route runoff north, then east, off -site,
bypassing dry detention pond, with C6.1 post -developed routed area/s. If area shown in
top image below bypasses dry detention pond, please revise relevant plan sheets, revise
routings, design, etc.
The bypass pipe is an ESC Phase 1 measure to allow offsite clean water to bypass the sediment
trap temporarily. Pipe has been removed from ESC phase II plan.
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.
Rev.1 Addressed.
C3.2:
2. Show break in SSF at stone weir outfall, ST2.
Break in SSF has been added
Rev.1 Addressed.
3. Label ST1, ST2 stone weir dimensions (L x W) in plan view.
Weir dimensions have been added to weir labels
Rev.1 Addressed.
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
Rev.1 Partially addressed. As follow-up; Please see / address New SWM Plan comment 21,
above.
Comment has been addressed bypass pipe has been removed from phase II.
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
Rev.1 Addressed.
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
Rev.1 Addressed.
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.
Rev.1 Not addressed. Please indicate, using Hydrocad analysis or other means, that pipe 301
capacity and riprap at pipe 301 outfall are sufficient to meet Q2-Vel./10-capacity (dry pond)
routed flows. Also, see dry pond riser structure detail (image, below). Routings include relevant
parameters, but do not explicitly address this comment.
Outlet Protection Sizing calculation has been included in calculations book.
8. Evaluate discharge velocity against riprap outfall, Str. 200 / VDOT ES (capacity appears
sufficient).
Riprap calculations have been added to calc book
Rev.1 Addressed.
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