HomeMy WebLinkAboutWPO202000007 Correspondence 2021-05-21608 Preston Avenue
P 434.295.5624
Suite 200 IF434.295.1800
T I M M O N S GROUP
Charlottesville, VA 22903 www.timmons.com
May 21, 2021
John Anderson
County of Albemarle
Dept. of Community Development
401 McIntire Rd, Rm 227
Charlottesville, VA 22902
RE: Hark Vineyards Tasting Room — VSMP Plan Review — WP02020-00007 - Comment
Response Letter
Dear Mr. Anderson:
We have reviewed all of your comments from (Rev. 2) April 22, 2021 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.
1. Sec. 1, Registration Statement is incomplete. Complete Sec. 1 as condition of VSMP /
WPO plan approval.
a. Sec. I.A. Operator/Permittee information: Section is blank; please complete.
(Rev. 1) Not addressed.
Section has been checked and is completed.
(Rev. 2) Not addressed; may be technical, submittal -related issue. Please flatten
.PDF prior to re-submittal..PDF preview welcome prior to formal resubmittal.
Review of remaining Registration Statement -related comments tends to indicate
this is a .PDF file flatten issue.
The SWPPP has been flattened prior to submission to help solve the issue.
b. c..,- I\/ ❑ /CSt FZA@teal .. eGt El@tee; !'.,..-...I„r..
c. See IV F GepAi,. an Plan of P,...,.lepi,. ent! please ,.h,.ek Review error;
withdrawn.
d. Sec. VI/Certification: Please complete. (Rev. 1) Not addressed.
Section will be completed once a contractor selection has been finalized.
(Rev. 2) Persists. File flatten issue?
The SWPPP has been flattened prior to submission to help solve the issue.
e. New: Sec. II.B., C., E., G.I — Complete all sections of Registration Statement.
Please QC
Sections were completed on previous submittal.
ENGINEERING I DESIGN I TECHNOLOGY
(Rev. 2) Persists. File flatten issue?
The SWPPP has been flattened prior to submission to help solve the issue.
2. Sec. 4, 5: Update these sections with revised ESC and SWIM plan sheets, once comments
are addressed. (Rev. 1) Persists.
Section have been revised with updated plans.
(Rev. 2) May persist.
Sections 4 and 5 have been updated with the revised ESC and SWM plan sheets
3. Sec. 6.A / Exhibit: Indicate location rain gauge. (Rev. 1) Addressed. As follow-up:
(Rev. 2) a, b, c, below, addressed.
a. Provide silt fence downslope of stockpile.
Silt fence has been provided around stockpile.
b. Provide depression / small trap to collect vehicle wash waters (not VESCH design
/small).
A depression has been called out to collect vehicle wash waters.
c. Provide catchment / small trap to intercept runoff from dumpster, mortar mix,
temp. toilets. These items are shown on ungraded slopes with no downslope
catchment, or barrier to overland flow.
Dumpster, mortar mixing station, and temporary toilets have been relocated and are
now uphill of a depression / catchment for runoff.
4. Sec. 6.E. — List named individual responsible for pollution prevention practices prior to
VPDES permit registration. (Rev. 1) Persists. List named individual prior to VAR10 CGP
Registration for state permit.
This section will be completed once a contractor has been selected.
Rev. 2 Persists. Applicant response (April 6 letter): 'This section will be completed once a
contractor has been selected.'
This section now lists the contractors name and information.
5. Sec. 8. — List named individual qualified to perform compliance inspections prior to
VPDES permit registration. (Rev. 1) Persists. List named individual prior to VAR10 CGP
Registration for state permit.
Section will be completed prior to registration permit once a contractor and subs have been
finalized.
Rev. 2 Persists. Applicant: 'Section will be completed prior to registration permit once a
contractor and subs have been finalized.'
A contractor has been selected and this section has now been filled out.
6. Sec. 9., Signed Certification: Individual who prepared SWPPP document must sign as
condition of VSMP / WPO plan approval. Albemarle cannot register project with DEQ
until SWPPP Sec. 9 is complete. (Rev. 1) Persists.
Section will be completed once a contractor has been selected.
(Rev. 2) Persists.
This section has been filled out and will be signed prior to SWPPP approval.
7. Sec. 11— Include copy of 26-p 2019VAR10 VPDES General Construction Permit. (Rev. 1)
Addressed.
8. Sec. 12 —Include template inspection forms. (Rev. 1) Addressed.
9. Include 2019 Notice of Termination form. (Rev. 1) Not Addressed.
Notice of termination has been included with SWPPP. See section 13
(Rev. 2) Addressed.
10. Revise SWPPP title to include ref. to VSMP / WPO2020-00007. (Rev. 1) Addressed.
B. Pollution Prevention Plan (PPP) —See above. Limited follow-up items.
The PPP content requirements can be found in County Code section 17-404.
(Rev. 2) Addressed.
C. Stormwater Management Plan (SWMP)
VSMP Regulation 9VAC25-870-108 requires the VSMP authority to approve or disapprove a SWMP. This
plan is disapproved; please see items 21, 31, below. The stormwater management plan content
requirements can be found in County Code Section 17-403.
1. A SWM Facility Easement Plat is required for this project. Rev. 1 Withdrawn. Initial
comment is revised to require stormwater management maintenance agreement, Sec.
17-415, which ensures county access for periodic inspection/maintenance, and
stipulates owner obligation to maintain SWM facilities. Platted easement is not,
however, required. Platted easement with deed is required for: subdivision
developments [14-428]; site plan developments [18-32.7.4.2]; and if a forest -open space
(FOS) area/acreage value is entered as post -developed land cover in VRRM.xIs [DEQ
Guidance Memo No. 16-2001, May 2, 2016]. Chapter 17 alone does not stipulate
easement requirements for SWM facilities. Ch. 14 and 18, however, do. This site does
not require a site plan and does not propose subdivision or FOS Easement; therefore,
platted easement and SWM facility deed are not required. A SWM Facility Maintenance
Agreement and surety/bond for SWM facilities are required.
A SWM easement is now shown on plan sheet C5.0. We will begin coordination with Ana
Kilmer for a SWM Facility Maintenance Agreement and surety/bond for the SWM facilities.
C0.0:
2. Revise title to include VSMP / WPO2020-00007. Rev. 1 Addressed.
3. Revise Note 2. Shift install detention piping to sequence step 8., or revise notes to
ensure detention system remains off-line until upslope areas are stabilized. Rev. 1 NA
— Design revised.
4. Source of topography is given as county GIS. Provide source of survey basis of design
(SWM facility / storm pipe design elevations). Rev. 1 Addressed.
5. Revise drawing index, C-1.3 to ref. Site Layout. A VSMP/WPO plan cannot
include/approve a site plan. Rev. 1 Addressed.
C2.0:
6. Identify and provide ownership data for adjacent parcels (TMP #, Owner name, deed bk.
-pg.). Rev. 1 Partially Addressed. As follow-up: Provide large scale image that depicts
entire development parcel, with every adjacent TMP identified (TMP#, owner, deed bk. -
pg.). Also: list intersecting road distance SE / NW.
An Adjacent Property Exhibit has been provided to display the required information above.
See plan sheet C0.1.
Rev.2 Addressed.
7. Recommend coordinate entrance location with VDOT. Acquire VDOT permits, as
needed. Rev. 1 Persists. Entrance is shown on C3.4.
Comment Acknowledged. VDOT coordination is underway.
Rev.2 Addressed.
8. Label critical slopes. Rev. 1 Withdrawn. No critical slopes in vicinity of development
(lot/building).
C4.0:
9. Revise sheet title to site layout. Rev. 1 Addressed.
10. Recommend label typical parking space dimensions. Rev. 1 Addressed.
11. Show yard drain outfall (Show connection to SWM system, or release point). Rev. 1 NA —
Design revised.
12. Provide 50' gas pipeline easement bk.-pg. reference. Rev. 1 Addressed.
13. Provide note listing depth (or suspected depth) to gas pipeline. (Rev. 1) Withdrawn.
14. Provide precautionary Note to contractor concerning grading within gas pipeline easement.
Rev. 1). Persists — Provide Note on C5.0.
A precautionary note has been added to sheet C2.0 and C5.0.
Rev.2 Addressed.
15. Provide retaining wall details; for example: type, length, Max. height. Rev. 1 NA— Design
revised. A retaining wall (15' high; C4.0, C5.0) is incorporated into building design to be reviewed
as part of building permit application review/ approval process.
Acknowledged.
16. Provide SWM facility description (material, slope, overall L x W x DIA x # lines). Rev. 1 NA —
Design Revised.
17. Recommend label post -developed improvements, i.e.: asphalt parking, concrete walk, etc. Rev.
1Addressed.
18. Label two culverts near vineyard entrance. Rev. 1 NA— Design revised.
19. Recommend show site water supply (well). Rev. 1). Addressed.
C-1.3:
20. VaRRm.XIs land cover summary post -development lists Final Post Dev Site Rv = 0.53; revise
Energy balance equation to use this post-dev Rv. Rev. 1 NA— Design revised.
21. Ensure energy balance equation indicates compliance. Rev. 1 Persists. Also, item 50., below.
Stormwater design has been revised to comply with Energy Balance for the disturbed areas
that will be concentrated in the post condition.
Rev. 2 Partially addressed. As follow-up: Please see email sent 03/08/20219:00 AM, which
includes: 'To be consistent with what we've required on other projects, the engineer should
show the flowrate and orifice size required to meet the energy balance in addition to the
flowrate resulting from the 3" orifice. They need to also request an Exception from the
regulations to discharge mor than what the energy balance allows. The request should be a
letter with a fee ($240) and the letter should compare the rates and provide justification for
using a 3-inch discharge.' If unable to meet the energy balance requirement with a 3-inch
orifice, please request an exception requesting to construct underground detention shown on
C6.0 with a 3-inch orifice, rather than 2.5".
Exception request has been submitted to the county and approved per email from Frank Pohl
on May 191h.
22. Provide Q(1) un-detained calculations, since methodology unclear. 14.31 cfs does not match C-
1.9 hydrographs. Label un-detained drainage divide in image. 'Overall drainage areas.' Align
graphic, routings, calculations, energy balance, and compliance narrative with aim toward
simplicity, and clarity. C-1.3 and C-1.9 provide a partial, somewhat confusing analysis of drainage
and SWM compliance data. Rev. 1 Design revised.
23. Revise using I.F. = 0.8. Engineering check, energy balance: Qpost = (0.8)(14.50)(0.20)/0.53 —
Qpost undetained. Rev. 1 Persists —Although design revised, this comment is relevant. Water
quantity compliance requires energy balance since proposed discharge is to a natural
conveyance (ref. review item 50., below). Note: Simply altering location of outfall does not
address comment. Given slopes across site, ELS is a non -viable stand-alone concentrated -to -
sheet flow transition device. Runoff must be detained (reduced) on this site.
Stormwater management for the site has been revised to include detention of the impervious
concentrated areas in the post condition. See sheet C7.0 for revised flood and channel
protection.
Rev. 2 Addressed, but please see item 21, above.
24. Provide post -developed impervious cover table, listing impervious area (sf) of: Rev. 1 Persists.
Rev.2
Addressed.
a.
Drive
b.
Walks
c.
Parking
d.
Buildings
'' Q
Bldg. 2
tee.
Impervious cover table has been provided under the Water Quality Calculations
on plan sheet C7.0.
25. Show existing structures (structures visible in GIS). Rev. 1 Addressed.
26. Label terrain contours; provide elevation labels. Rev. 1 Addressed.
27. Label roads beyond property boundary. Rev. 1 Addressed.
28. If nutrient credit purchase proposed, coordinate with Ana Kilmer, Management Analyst, prior to
purchase. Rev. 1 Persists— Plan proposes 1.59 lb nutrient credit purchase.
Comment Acknowledged. Nutrient Credit purchase will be coordinated with Ana Kilmer prior
to purchase.
Rev.2 Persists.
Coordination for nutrient credits will be coordinated with Ana Kilmer prior to purchase.
C4-4 Design Calculations and Narrative, Feb-5, 2021 (Timmons Group)
29. Culvert 4 proposed 27.5% exceeds Max. 16%. Pipe grade steeper than 16% requires anchors.
Ref. VDOT drainage manual, 9.4.8.7, maximum grades. Rev. 1 Not addressed. Though design
has changed and culvert 4 does not exist, design proposes pipe 101, 19.74%. Provide anchor
block detail, notes, narrative, sequence, etc. to guide installation of anchors for pipe > 16%
slope, per VDOT Drainage Manual standards. Provide / show anchors, anchor detail, noes,
narrative, sequence, etc., requisite for pipe 101 installation, for plan approval. Ref. Calc. Report,
p. 5. Note: "Slopes in excess of 16% are not preferred because of the need for anchor blocks.
When anchor blocks are used, they should be installed at every other pipe joint, as a minimum.
(See Special Design Drawing No. A-73 and MA-73 for Anchor Details for Concrete Pipe).
Corrugated pipe may be used on steep slopes in situations similar to those where shoulder slot
inlets are proposed. Corrugated pipe should not be used in areas where the flow is expected to
carry an abrasive bed load or that have PH and resistivity factors beyond the ranges specified in
the Allowable Pipe Type Table C in Standard PC-1 of the VDOT Road and Bridge Standards. (See
VDOT's Road and Bridge Standard PI-1for Anchor Details for Corrugated Pipe). In steeper terrain,
large elevation differences can be accommodated using drop structures, otherwise known as
"step down" manholes, to reduce the pipe gradient.
The storm system has been revised and pipe slopes have been revised to be less than 16%.
(Rev. 2) Addressed.
30. Design, show, and label riprap outfall protection for culverts 1 and 5. (Rev. 1) NA— Design
Revised.
31. Provide LD-229, storm culvert design tables for all culverts. Avoid flow velocities in excess of 10
fps. Rev. 1 Partially addressed. As follow-up:
a. List pipe 101 outfall V 2-yr.
Comment Noted. Culvert Calcs are now provided
Rev. 2 Not addressed. Velocity calculation is provided for pipe 201, at site
entrance. Please provide V 2-year for pipe 101, which is site storm outfall.
The 2 year velocity is now being used for pipe 101. An updated LD 229 has
been included on the calc book.
b. Provide outfall protection (OP) sized for outfall flow / velocity.
Outfall protection has now been provided and called out on plans. Based on
velocity Class I riprap has been used and sized to meet or exceed VDOT Road
and Bridge Standards EC-1.
Rev. 2 May Persist. Able to evaluate riprap once site outfall velocity reported.
Please alert if pipe 101 V 2-year is presented on plan or calculation booklet and
overlooked.
The 2 year velocity is now being used and can be found on the LD-229 in the
calc book.
c. Label pipe outfall riprap dimensions (L x W x D).
Pipe outfall riprap dimensions are now included on the plan sheet.
(Rev. 2) Addressed.
32. Provide storm profiles: label INV IN/OUT, rim, etc. Rev. 1 Addressed.
33. Label structures. Use VDOT nomenclature. Rev. 1 Addressed.
34. Provide Nyloplast typical details, as needed. Rev. 1 Addressed.
35. (C5.0) Provide flow arrows to indicate direction of flow in pipes. Rev. 1 Not addressed.
Flow arrows have been provided as requested. See sheet C5.0.
(Rev. 2) Addressed.
36. If culvert 2 passes beneath proposed retaining wall, show retaining wall in storm profile. Rev. 1
NA — Design revised.
37. Provide design details of storm detention system; see comments elsewhere (slope, DIA, overall
length, # lines, etc.). Rev. 1 NA— Design revised; detention eliminated.
38. If storm detention is a Mfr. System (ADS, Contech, etc.). provide manufacturer recommended
installation, and periodic maintenance guidelines (on the plans). Rev. 1 NA — Design revised.
39. Ensure manways to detention system are accessible. Provide clear view of 15" HDPE end cap
and debris cage from above, without requiring inspectors to enter 4' MH confined space. Rev.
11 NA — Design revised.
40. Culvert 5: Outfall is shown at elev. 602', while invert out is listed as 600.0'. Revise for
consistency. (Rev. 1) NA — Design revised.
41. Provide swale adequacy calculations (pre -post listed as 3.35 and 3.55 fps, respectively). Provide
10-yr swale capacity (cfs) and 2-yr swale velocity (fps) calculations. Rev. 1 NA — Design revised.
42. Provide culvert 3 velocity / capacity calculations; see comments elsewhere re. LD-229. Rev. 1
NA — Design revised.
43. Show, design, and label outfall protection, culvert 3. Provide channel protection, as needed, for
drainage formed by proposed and existing contours downslope of culvert 3. Rev. 1 NA— Design
revised, but please see ESC Plan, item 14.h., below.
Comment Acknowledged.
44. Recommend steeper slope for culvert 2, flatter slope for culvert 4. Rev. 1 NA — Design revised.
C-1.8:
45. Provide additional plan / profile data for detention system: (Rev. 1) NA — Design revised.
a. Elev. base of bedding,
b. Label hatch to 15" pipe,
c. Show debris cage for 2.5" DIA orifice in end cap,
d. Provide additional endcap detail (specify watertight, means of affixing to 15"
HDPE, end cap material, etc.),
e. Label culvert 5,
f. Label MH diameter,
g. Label / revise rectangular image in right-hand profile view of detention structure,
which appears inconsistent with plan view.
46. Provide debris cage detail (2.5" DIA orifice). Rev. 1 NA— Design revised.
47. Add .PDF image of Construction Record Drawing (As -Built) for VSMP to the plans. Rev. 1
Addressed.
48. Submit easement plat. Easement plat must be recorded prior to VSMP /
WP0202000007 approval. Rev. 1 Review error / withdrawn. Also, SWIM review item 1.,
above.
New:
49. C8.0:
a. Reconcile pipe 101 profile 12.00% slope with calc. report, p. 5, pipe 101 slope
19.74%.
The storm system has been updated and pipe calcs have been revised
accordingly.
Rev.2 Addressed.
b. Str. 104: Provide label requiring %:" steel plate in floor of MH.
Per VODT Design Standard 9.4.8.7, a steel plate is only required in a manhole
where the inlet pipe and outlet pipe are greater than 4' apart and the flow is
either continuous live flow, carrying abrasive materials, or the size of the main
pipes is 48" or greater. There is no live flow through this system and therefore
a steel plate is not required for the manhole.
Rev.2 Withdrawn.
c. Recommend Note requiring 95% compaction beneath pipe 105 / str. 106, since
in fill sections.
Comment Acknowledged. A note has been added to the storm profile sheet requiring
compaction for structures located in fill.
Rev.2 Addressed.
50. 9VAC25-870-66.D./copied from
https://law.lis.virginia.gov/admincode/title9/agency25/chapter870/section66/ D.
Increased volumes of sheet flow resulting from pervious or disconnected impervious
areas, or from physical spreading of concentrated flow through level spreaders, must be
identified and evaluated for potential impacts on -down -gradient properties or
resources. Increased volumes of sheet flow that will cause or contribute to erosion,
sedimentation, or flooding of down gradient properties or resources shall be diverted to
a stormwater management facility or a stormwater conveyance system that conveys the
runoff without causing down -gradient erosion, sedimentation, or flooding. If all runoff
from the site is sheet flow and the conditions of this subsection are met, no further
water quantity controls are required.:
a. Initial design included detention, a SWWM facility that would limit runoff
without causing down -gradient erosion, sedimentation, or flooding.
The design has been updated to include detention for the concentrated runoff
from the proposed impervious areas in the post condition.
b. Please revisit / restore stormwater management facility design to this VSMP.
The design has been updated to include detention.
c. Revise / delete reference in plan narrative, or calculation report that water
quantity is met by sheet flow, without detention, with an ELS. Downgradient
slope / contours indicate a nearly proximate existing natural conveyance channel
will concentrate increased volumes of sheet flow.
Acknowledged. Design has been updated.
d. Sheet flow Vol. increases with this project with construction of significant
impervious land cover.
The design has been updated to include detention for the concentrated runoff
from the proposed impervious areas in the post condition.
e. Divert site runoff to a stormwater management facility or a stormwater
conveyance system that conveys the runoff without causing downgradient
erosion, sedimentation, or flooding.
The design has been updated to include detention for the concentrated runoff
from the proposed impervious areas in the post condition.
f. Water quantity compliance is not met with this design; please see images below.
The design has been updated to include detention for the concentrated runoff
from the proposed impervious areas in the post condition.
(Rev. 2) Addressed. The design has been updated to include detention.
51. Engineering urges applicant to coordinate septic field / plan review with VDH at earliest
convenience:
Comment Acknowledged
(Rev. 2) Comment acknowledged.
D. Erosion and Sediment Control Plan (ESOP).
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..
C-1.5:
1. It is not apparent how proposed buildings, [and] parking, And 51444 dAtPR"^^ can be
built while maintaining per diversions. Ensure diversions and all ESC can be
maintained, as proposed, throughout construction. SheW ...,...,.sed � passible inteFAa'
ArPPAA h..a.,...... co ccn ARGI A9tFWGtiQR site. (Rev. 1) Persists.
Notes have been added to Erosion and Sediment Control Phase 2 to better convey to
the contractor and planner the construction sequence that shall occur in order to
maintain acceptable Erosion and Sediment Control measures until site stabilization is
completed.
(Rev. 2) Addressed.
2. Label OP1, OP2. Rev. 1 NA —Design Revised.
3. Recommend initial location for staging and parking, solid waste dumpster, port-a-john,
and concrete washout that does not require relocation for installation of detention
system, or culvert 5. LLev. 1 Addressed.
4. Concrete wash -out station must drain to a trapping device; show location of trapping
device. Rev. 1 Not addressed.
A wash -out trapping device has been added to the Pollution Prevention Plan and
called out accordingly.
(Rev. 2) Addressed.
5. Provide design details for level spreader (ELS) at outfall of culvert 3. Ref. VA DEQ
Stormwater Design Specification No. 2, Table 2.2 for ELS design criteria (13 lin. Ft. per
each 1 cfs of inflow). (Rev. 1) May persist. An ELS may transition concentrated release
from a detention system / SWM facility to sheet flow. Provide design details for any ELS
that persists as a design feature.
The design has been updated to include detention for the concentrated runoff from
the proposed impervious areas in the post condition. Energy balance is being met for
the concentrated stormwater outfall and the ELS has been removed.
(Rev. 2) Addressed.
6. Include ELS, culvert 3, in SWIM narrative. Rev. 1 NA— Design Revised.
7. Label all culverts on this plan sheet. LLev. 1 Addressed.
8. Revise CE symbol at site entrance to PCE (paved entrance). (Rev. 1) Not addressed.
CE symbol has been revised accordingly
(Rev. 2) Addressed.
9. Provide additional existing contour labels, to aid review and analysis. Rev. 1
Addressed.
10. Show / label sanitary line (crossing) in culvert 5 profile (proposed san. Line from building
to septic field). (Rev. 1) Not addressed. Show / label sanitary line (crossing) in pipe 103
profile, C8.0 (FM crossing x 2).
The stormwater system has been revised and no longer crosses the proposed sanitary.
(Rev. 2) Addressed.
C-1.7:
11. Provide specific OP details (OP1, 0132), Rev. 1 NA— Designed revised.
12. Provide standard VDOT details: Rev. 1 Persists.
(Rev. 2) Addressed.
a. PB-1 (pipe bedding)
b. ST-1 (safety steps)
c. IS-1 (inlet shaping)
Details have been added to plan sheet C1.0
New:
13. C3.1: Provide paved wash rack detail; p.8, ACDMS - link:
A paved wash rack detail has been added to plan sheet C3.1.
(Rev. 2) Addressed.
14. Provide ESC phase interim to phase 1 (C3.2) and 2 (C3.3) that shows phase 2 final site
grading with phase 1 sediment traps:
Rev. 2 Items a. — k., addressed, via labels, ESC sequence notes, measures, and
linework.
a. Phase 1 sediment traps (ST1, ST2) control runoff from 3.82 Ac.
Phase 1 ESC diversions have been designed to allow the phase 1 drainage areas
to closely match the phase 2 drainage areas and notes have been added to
maintain the similar drainage divide and areas to each trap through
construction.
b. Phase 1 indicates trap placement, diversions, but apart from ST grading, no
grading, whatsoever.
Correct. The existing site allows, and phase 1 diversion dikes allow for the site
to drain to the proposed sediment traps without the need for additional site
grading.
c. Phase 2 indicates final, built condition, but no sediment traps.
Sediment trap outlines and notes have been added to Phase 2 to better convey
that all E&S measures must remain in place until the site is fully stabilized as
also required by the sequence of installation narrative on sheet C3.0.
d. The interim phase, where all site work / grading and building construction occur
while STs receive diverted runoff during constructive phase, are not shown.
Drainage divided and notes have been added to Phase 2 to ensure E&S
measures are required and must remain until site is fully stabilized.
e. No ESC information is provided for the entirety of site grading / building
construction.
Phase 2 has been revised to show and note E&S measures that must remain
until the contributing drainage areas are stabilized.
f. Phase 2presents sparse perimeter controls unequal to challenge of controlling
runoff from 3.82 Ac. DA, once diverted to sediment traps, now released to
newly graded fill slopes.
Notes have been added to phase 2 to ensure that diversions and sediment
traps remain in place until site is stabilized. Parking layout and storm have also
been revised which will decrease flow from impervious areas to newly graded
fill slopes.
g. Final grading proposes uniform contours that in theory support sheet runoff,
once stabilized.
Comment acknowledged.
h. Stabilization may not occur for weeks, or months. Until site is stabilized,
sediment traps must operate with relocated diversions routing runoff from
graded slopes to same / similar traps, with diversions designed to convey runoff
to the traps. Also, please consider temporary slope drain/s.
Per the E&S narrative on sheet C3.0, all E&S measures are to remain in place
until site has been fully stabilized and signed off on by the E&S inspector.
Notes have been added to phase 2 ESC plan to reiterate this. Divisions are
located such that they can remain in place through final grading. A curb and
gutter have been added along the top of the slope from the parking and a note
about temporary division to a proposed inlet has been added to limit flow
down slope.
In ESC phase 2, no ESC or channel design is provided for concentrated runoff at
intersection of existing grade and proposed grade at NW side of site. The total
vertical fall on the NW side of the site is 40' (658' — 618'). Design permanent
storm conveyance channel (may be grass -lined if velocity non -erosive / provide
EC-2, EC-3 matting, as needed) where runoff concentrates. Evaluate channel
velocity, and armoring (EC-2, EC-3), as needed (blue arrow below).
Slope edge has been regraded to have a gradual tie into existing grade and
avoid concentrated flow as much as possible. A channel calculation has been
run and it is determined that the velocities are non -erosive in the final
condition. See sheet C6.0 for calculation and channel cross-section.
j. Please consider permanent surface water diversion to collect / divert runoff from
edge of parking lot to base of slope, rather than across slope face. Design
assumes slope stability, even if parking lot runoff releases across 15' -20' H fill
slope. Sheet runoff from impervious areas across newly constructed fill slopes of
this height will likely cause rill erosion, which may worsen, or prove difficult or
expensive to fix, once rills established. This is a recommendation. Also, see 18-
4.3.3.C.4.
Curb has been added to the parking areas to reduce runoff from pavement to
the slopes.
k. C3.3: Perimeter controls for expanse of 15-20' high fill slopes are inadequate, or
simply not provided. Provide adequate phase 2 perimeter controls; see image,
below:
A temporary diversion dike is provided in phase 1 and shall remain in place
until the entire site is stabilized and approved by the E&S inspector.
15. C3.2:
a. Label ST floor dimensions in plan view (L x W).
Dimensions have been added to the Sediment Traps as requested.
(Rev. 2) Addressed.
b. Label ST stone weir dimensions, plan view (L x W).
Stone Weir dimensions have been added to the plans as requested.
(Rev. 2) Withdrawn.
16. New: Recommendation unrelated to WPO (Note, An SDP Application is not required;
agricultural use): Since project does not require a site or road plan, VDOT will not see
information shown on C5.1, Sight Distance Profile. Recommend coordinate entrance
design at Markwood Road with VDOT since sight distance (left) profile indicates SDL is
within 3" of existing grade at SDL station 350'. VDOT may offer recommendation; in any
event, post -construction adjustment would only require slight additional cut beyond
public RW, on development property, to ensure unobstructed SDL, left (so, not a critical
issue).
Acknowledged. VDOT has reviewed and noted sight distance will be field verified
after grading is completed.
17. New: Recommend revise C6.0 SR 664 — Markwood Road label to read 'prescriptive'.
Typo; not critical.
Spelling has been corrected on plans.
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 or email at
jonathan.showalter@timmons.com .
Sincerely,
Jonathan Showalter, PE
Project Manager