HomeMy WebLinkAboutWPO202200020 Correspondence 2023-01-13SHIMP ENGINEERING, P.C.
Design Focused Engineering
January 11t^, 2022
David James
Djames2@albemarle.org
Albemarle County
401 McIntire Road
Charlottesville, VA 22911
Regarding: WP0202200020 South Pantops - Parcel 20R
Review Comments
Dear Mr. John,
Thank you for your review of the SDP Plans for South Pantops-Parcel 20R. We have revised our plans per most
recent comments dated June 8th, 2022. Please see below for a detailed response to each of your comments.
Albemarle County Planning Services (Planner)
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.
Registration Statement:
a)
Sec.
1 B. - Check box ok
b)
Sec.
11 F. - Change to Albemarle Count, ok
c)
Sec.
11 H. - Check box ok
d)
Sec.
III - Complete prior to permit issuance To be determinated
e)
Sec.
V - Sign & date ok
2. Complete Section 9. Signed Certification prior to plan approvai Signed
3. Complete other sections prior to pre -con.
B. Pollution Prevention Plan ( PPP)
The PPP content requirements can be found in County Code section 17-404.
1. Appears complete; revise as needed. Checked
C. Stormwater Management Plan ( SWMP)
VSMP Regulation 9VAC25- 870- 108 requires the VSMP authority to approve or disapprove a SWMP.
This plan is denied, and the reasons are provided in the comments below. The stormwater management
plan content requirements can be found in County Code section 17-
403.
Show the Forest & Open Space easement(s) areas to be protected. According to VRRM 4.13ac
F/ OS pro
New VRRM Dev. Spreadsheet and VRRM Map has been updated and added on Sheet C9
2. A swm nary...,... �� ui need to b, included on the plans.
Narrative has been included with the DA Maps. See sheet C9 & C10.
3. 1 would prefer that information on the type and location of stormwater disch ^ predevelopment
and postdevelopment drainage areas be shown on the plans rather than � n talc. packet.
The Drainages area maps has been added on the plans. See Sheet C9 & C10
Also, you can see the Drainage area hatch colors in the swm packet.
4. Calculations packet:
a) Pg. 16 - Revise title of map to " POSTDEV...".
Revised.
b) Your pre- & post- development drainage area totals should match
The offsite drainage area now matches but, in this case, our Pre -Development onsite drainage
area is smaller than post -Development onsite (onsite= disturbed) drainage area because the
post -Drainage area re -directs additional onsite area to the POA at the channel. This
Development slightly increases the drainage area to the channel.
c) It' s not clear from the mans h^.. ^.� are reducinc ^ff,;* i^ pervious area ( 1S/ 8S)
postdevelopment.
This was a data entry typo which has been corrected.
d) Label/ show offsite & onsite drainage areas
Offsite & onsite drainage areas have been labeled on the drainage area maps.
e) Pg. 24 —
i. Please cite the page number, Number was added on each page
ii. Clarify why you are subtracting Max Qdev, from the Qprcdev? Max Qdev determined
( 0.15efs) is less than the Achieved Reduction ( 0.89efs).
This analysis now uses the DEQ Offsite run -on EBE analysis, so this comment is no
longer applicable. Note: Limits of Disturbance area has been added, because we got
the new survey topo area. Also note, we have utilized permeable paver driveways to
help achieve compliance with the energy balance equation.
iii. Use the Energy Balance (offsite) equation. Consult the Plan reviewer SWM participant
guide.
Noted, this has now been provided.
f) Please clarify: On pg. 24 you state you' re meeting flood protection under 66-C(2)b, but on pg. 3
for flood protection it looks like your trying to meet 66- C(1).
i. You're not showing you meet 66- C(2) b, Qpost> Qpre.
This development complies with 9VAC25-870-66-C(3).c
We have analyzed channels up to the limits of analysis at the mapped flood plain
g) VRRM - Please use New development spreadsheet. The parcel is undeveloped.
Updated New VRRM Spreadsheet. New swm forest / open space to be dedicated is 3.26
acres.
h) h. Provide inlet drainage area map and assumed values to match tale. table.
Post- dev structure (channel and Inlet) drainage area map has been added on sheet C9.
i) i. Provide channel adequacy/ protection is met from the Al discharge point to outfall natural
channel (i. e. portion of ex. manmade channel). 66- 13(1)
The Ld-268 table has been used to demonstrate that 2-yr velocity and 10-yr depth at the
concrete channel is adequate up to the outfall point. See table on sheet C9
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, 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. Cover —
a. Provide date( s) of LIDAR data.
A year has been provided on Cover Sheet.
b. Provide date of tieio verification of topography & existing conditions.
Information about Boundary and topographic survey has been provided on the cover
sheet
Please show LOD on the existing conditions sheet.
Limits of Disturbance have been added to the Existing conditions sheet
3. Show demolition operations.
Demolition operations are labeled (DEMO) on Ex. Conditions sheet.
4. Show cxisting trccnnc.
Existing Tree line has been shown. See sheet C2
Show accurate horizontal depth ( batter) of retaining wall.
Retaining wall information has been added on Sheet C4
Retaining wall information:
Max Hight=10 It
Max Thickness =1.0 It + 1.25 ft = 2.30 drawn
Batter =1.25 It
6. Show geogrid extent of retaining wall.
Geogrid hatch has been added along to the retaining wall.
Depth: 8.0 ft
7. Label TW/ BW elevations at each bend and wall ends.
TW/BW elevation has been provided.
8. Tie contour lines along new road to the retaining wall.
Contours lines have been tied to the retaining wall.
Note: Please submit retaining wall design & computations with the site plan. Separate building
permit required.
Comment noted. We have this in progress we will submit it separately.
10. Show all proposed contours at 2' intervals.
Contours have been updated with the new topo survey.
11. Reduce grade to 2: 1 or less adjacent to lot 1.
Update grate, to be 2:1 Slope.
12. Provide B/ M ( VAESC HB, 3. 36) between lots 5 & 6, and adjacent to lot 1.
Blanket Matting has been added on Sheet C5.
13. Where grade over 3: i provwe low -maintenance ( not grass) groundcover.
A note has been added on Sheet C7.
14. Show a staging and stockpile area. Show SF around stockpile.
Staging and stockpile area are shown on Sheet C6.
15. Show temporary construction easement for offsite improvements.
Not need, access easement already exits. See sheet C2.
16. Provide letter of permission from VDOT for work in the ROW prior to disturbance.
Letter should be provided from the contractor.
17. Provide volume estimate of cut & fill balances.
Estimated Fill is 4,000 cubic yards. See cover sheet.
If you have any questions, please do not hesitate to contact me at odria@shimp-engineering.com, or you may contact
keane Rucker at keane@shimp-engineedng.com or by phone at (434)-227-5140.
Best Regards,
Odria Barefoot -Diaz
Shimp Engineering, P.C.