HomeMy WebLinkAboutWPO202000043 Correspondence 2020-11-23L I N E + G R A D E
C I V I L E N G I N E E R I N G
November 20, 2020
TO: Department of Community Development
401 McIntire Road
Charlottesville, VA 22902
ATTN: David James
RE: Airport Road Sheetz— WPO-2020-00043
Mr. James,
On behalf of Airport Plaza, LLC we offer the following responses and plan revisions to
comments dated October 14`h, 2020. Our Responses are in bold italic text below each
comment.
Engineering — David James
General
1. VSMP Application -Please provide owner's correspondence info.
The application has been revised to include the owner's contact info. See
attached VSMP application.
2. The WPO/VSMP & FSP need to be separate plans.
The WPO/VSMP plan has been separated from the FSP. Please note both plans
are being submitted as separate submissions with a separate comment
response letter for each. Although separated, sheet numbers remain the same
as the previous submission, except where explicitly noted in our responses. See
attached documentation.
3. Cover
a. Please add the WPO# under title.
b. Please remove the VDOT Design Criteria, Submittal Log, and Signature
Panel.
c. Please remove sheets C0.2, C2.6 thru C3.3, C4.3, C9.0, C9.1, A1.0, A1.1
from the WPO plan.
The WPO number has been added to the title, and the listed sheets have been
removed from the set. Please note C0.2 remains, as it now contains an overall
legend for the plans.
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CIVIL ENGINEERING
113 4`" STREET NE, STE. 100
CHARLOTTESVILLE, VA 22902
LINE-GRADE.COM
Airport Road Sheetz — WPO-2020-00043
1" Comment Response Letter
November 20, 2020 1 Page 2
4. Add in the County's'General construction notes for Erosion and Sediment
Control plans', and 'General construction notes for Stormwater Management
plans'.
The general notes for Erosion and Sediment Control plan and Stormwater
Management plans have been added to the plans. See sheets C2.0 & C7.7.
5. Obtain VDOT entrance permits prior to start of construction.
Acknowledged. VDOT entrance permits will be obtained prior to construction.
VDOT has acknowledged the currently revised design is satisfactory.
6. Record any offsite easements prior to start of construction.
The offsite temporary construction and permanent shared access easements
have been recorded.
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.
1. Registration Statement:
a. Sec. I. A. — Provide Contact person & Primary Email information prior to
VSMP plan approval.
b. Sec. IV. C. — Part of parcel 32-39 lies in the County's MS4.
c. Sec. IV. F. — Please answer yes or no.
Comment noted. These changes have been made in the SWPPP Registration
Statement.
Pollution Prevention Plan (PPP)
The PPP content requirements can be found in County Code section 17-404.
1. Show where any fueling/fuel storage, chemical storage locations are on the PPP.
Also, show locations where concentrated stormwater discharges (Ex. Spillway
from VDOT basin, X-7, X-2).
The fueling, fuel storage, and chemical storage locations have been labeled on
the PPP. Concentrated stormwater discharges are now also labeled.
Please note that the spillway from the VDOT basin is an emergency spillway
and does not receive flows except in extreme rainfall events (greater than 10-
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GRADE
CIVIL ENGINEERING
113 4`" STREET NE, STE. 100
CHARLOTTESVILLE, VA 22902
LINE-GRADE.COM
Airport Road Sheetz — WPO-2020-00043
1" Comment Response Letter
November 20, 2020 1 Page 3
year return periods). X-7 also does not receive flow from this site, but from the
adjacent property (see drainage divides on sheet C2.6).
Stormwater Management Plan (SWMP)
VSMP Regulation 9VAC25-870-108 requires the VSMP authority to approve or
disapprove a SWMP. This plan is disapproved, and the reasons are provided in the
comments below. The stormwater management plan content requirements can be
found in County Code section 17-403.
1. Unfortunately, no infiltration BMP practice is allowed at this site due to gas
stations & car washes being a stormwater hotspot (VADEQ, BMP Spec#8, p.21).
DEQ Spec. #8 identifies areas where infiltration practices are restricted. No
infiltration practices are proposed. The proposed bioretention filters are
governed by DEQ Specification No. 9. On page 15 of this specification, the
design of bioretention filters within designated hotspot areas is addressed. In
short an impermeable bottom liner and underdrain must be installed to treat
hotspots. This is specified on the plans, as is shown on BMP profiles on sheet
C7.5 and in the material list under the BMP filter section on sheet C7.6. No
changes made.
2. C7.2:
a. Please provide VRRM spreadsheet for verification (email is fine).
b. Please provide Letter of Availability from nutrient entity provider.
The VRRM excel spreadsheet will be provided digitally with this submission via
email. Please note A letter of availability was previously included on sheet C7.2.
3. C7.5:
a. BMP A - Runoff from 15" pipe could short circuit to riser structure.
Provide some alternate design or configuration to achieve 0.3 min.
b. Bioretentions (#1) - Provide a form of pretreatment (Section 6.4). C7.6
does depict a Gravel flow spreader, but it's not called out or shown in the
BMP plan views. Pre-treatment should be located at the concentrated
outflow, but located outside of biorentention's bed surface area.
As shown in detail 3 on sheet C7.6, the riser structure for both BMPs is elevated
above the soil media surface. This prevents short-circuiting of flows (runoff is
forced to pond up prior to reaching the lip of the riser). This method of short-
circuit prevention is endorsed by DEQ specification No. 9 on page 22.
The proposed gravel flow spreaders are now labeled specifically in the BMP
plan views. The geometry of the gravel flow spreaders has been revised to
locate them outside of the soil media surface. See revised sheet C7.5.
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CIVIL ENGINEERING
113 4`" STREET NE, STE. 100
CHARLOTTESVILLE, VA 22902
LINE-GRADE.COM
Airport Road Sheetz — WPO-2020-00043
1" Comment Response Letter
November 20, 2020 1 Page 4
4. C7.4 -Please also provide channel design & liner needed from SD-12 to channel.
The short channel downstream of SD-12 has been designated B2. A new
channel cross section and computation can be found on sheet C7.4. The design
flow used in the computation is inclusive of the outflow of SD-12 and flow from
channel B. See revised sheet C7.4.
5. Bioretention setbacks (Section 5):
a. BMP A-
i. It appears that the car wash is within 10' of the facility and must
be located outside.
ii. It appears that water lines are within 5' of the facility and must
be located outside.
iii. It appears that the facility is located within 35' of a sanitary line
and must be located outside.
iv. Gas & cable lines can cross under the facility, but you must show
that these lines are protected & can be accessed (repaired)
without disturbing the facility.
The shape of BMP A has been adjusted to provide SO' of horizontal clearance
with the car wash building and 5' of horizontal clearance with the water service
line. The sanitary line is not a septic drain field, so the applicable setback
distance from the facility is 5, per page 16 of DEQ BMP specification No. 9. The
gas service line now has an encasement where the line passes within 5' of the
facility. See revised sheet U.S.
b. BMP B— It appears that the facility is located within 35' of a sanitary line
and must be located outside.
As discussed in the 1116120 meeting with staff, the sanitary line is not a septic
drain field so the applicable setback distance from the facility is 5, per page 16
of DEQ BMP specification No. 9. The current layout satisfies this setback.
6. C8.1 (Section 5.8) —The landscape plan shows a hatched area for the
bioretentions, but does not indicate what plants or bio-seed mix is used there. -
75% (min) plant surface coverage needed within 2yrs.
The landscape plan has been updated to show plantings within the bioretention
areas. See revised sheet C8.1.
C7.0/7.1— Your pre -development land cover areas, specifically forest/open space
area, doesn't match land cover areas found in GIS. This is what the 2013 land
cover overlay looks like: [see image from comment letter]. Please provide an
accurate account of land coverages values to justify pre -/post- runoff quantity
analysis, and VRRM worksheet.
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CIVIL ENGINEERING
113 4`" STREET NE, STE. 100
CHARLOTTESVILLE, VA 22902
LINE-GRADE.COM
Airport Road Sheetz — WPO-2020-00043
1" Comment Response Letter
November 20, 2020 1 Page 5
As discussed in the 1116120 meeting with staff, the land cover areas calculated
are measured directly from the actual ground survey performed in 2020 (see
attached survey). GIS is inherently limited in its mapping capabilities and is not
relied on to show compliance with state regulations. The land cover tabulations
shown on sheets C7.0 and C7.1 accurately reflect the actual land cover
conditions and have been field verified by the engineer of record.
8. Please provide SWM routing/ponding reports: Summary of pre-/post-dev. runoff
values for Energy Balance is not enough.
A stormwater calculation binder accompanies this submission.
9. Provide manufacture's long-term maintenance for the UD system & Specs. What
are the orifice or weir controls present (locations)? Show the release rates for
each. Show the design storm elevations at these control release locations.
Two sheets have been added detailing the proposed detention system.
Detention calculations have also been included with this submission. See new
sheets C7.7 and C7.8.
10. Provide list of materials, cost -estimate for the UD system.
We are awaiting this material and cost estimate from the manufacturer and
will email it to the County upon receipt.
11. C6.2 — For storm pipes operating under pressure flow (HGL above) provide that
these pipe joints & connections are made water -tight.
A note has been added to BMP profiles and to sheet C6.2 to this effect.
12. Provide inlet shaping (IS-1) at X-2.
Inlet shaping is proposed at all inlets, as notated below the inlet computations
table on sheet C7.4 and in the notes on sheet C6.2.
13. Reduce spread to under 10ft for SD-11.
Inlet SD-11 has been upsized to 8' in length, resulting in a spread that is less
than 10'. See revised sheet C7.4.
14. Show that the entrances won't flood during 25-yr storm. Show 100% capture of
flow will happen at entrances.
Per meeting with County staff on 111612020, it was determined that the
applicable regulation is that no concentrated flows greater than 1 cfs in the 10-
year design storm may flow across travel ways or entrances. As can be seen on
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CIVIL ENGINEERING
113 4`" STREET NE, STE. 100
CHARLOTTESVILLE, VA 22902
LINE-GRADE.COM
Airport Road Sheetz — WPO-2020-00043
1" Comment Response Letter
November 20, 2020 1 Page 6
sheet C7.4, inlets SD-17 and SD-19 bypass less than 1 cfs across the proposed
entrances in the 10-year storm.
Erosion and Sediment Control Plan (ESOP)
Virginia Code §62.1-44.15:55 requires the VESCP authority to approve or disapprove
an ESOP. This plan is disapproved, and the reasons are provided in the comments
below. The erosion control plan content requirements can be found in County Code
section 17-402.
1. Sheet C2.2, 5.0, etc.: Please tie in 557', 558' contours along west entrance.
The proposed 557 and 558 contours were previously tied into the existing grade
correctly. The limits of disturbance line was pushed out past the tie-in points of
these contours because existing gravel will be removed in this area, and the
surface restored to existing grade. To further clarify this surface change, the
proposed 557 and 558 contours have been drawn on top of the existing 557 and
558 contours up to the limits of disturbance line.
2. Provide low maintenance (not grass) ground cover specified on the plans where
grades are steeper than 3:1. [DSM, Sect 8A]
Proposed grades do not exceed 3:1.
3. Please confirm that you will not be using the existing entrance off Rt. 29 as a
construction entrance.
Correct construction traffic will utilize the construction entrance at the Airport
Road entrance only.
L I N E +
GRADE
CIVIL ENGINEERING
113 4`" STREET NE, STE. 100
CHARLOTTESVILLE, VA 22902
LINE-GRADE.COM