HomeMy WebLinkAboutWPO202000032 Correspondence 2020-07-20SHIMP ENGINEERING, P.C.
Design Focused Engineering
July 17, 2020
David James
County of Albemarle
Department of Community Development
401 McIntire Road, North Wing
Charlottesville, Virginia 22902
RE: Response Letter #1 for (WP0202000032) 1300 Richmond Road — Flow Automotive
Dear David,
Thank you for your review of the VSMP plan for 1300 Richmond Road. This letter contains responses to
County comments dated July 6, 2020.Our responses are as follows:
A. General
1. Cover —Add `WP0202000032' under title.
RESPONSE: This was added to the cover sheet under the title.
2. Submit a floodplain development permit for disturbance in the floodplain.
RESPONSE: A floodplain development permit with no floodplain impact has been submitted.
B. 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 ESOP, (3) a SWMP, and (4) any TAML measures necessary.
1. Registration Statement:
a. Add `County of Albemarle' under Section W.E.
RESPONSE: Completed.
b. Check the yes box under Section V.B.
RESPONSE: Completed.
C. Pollution Prevention Plan (PPP)
The PPP content requirements can be found in County Code section 17-404.
1. Show staging, stockpile, borrow, concrete washout locations on the PPP. Also, show locations
where concentrated stormwater may discharge.
RESPONSE: Staging areas, concrete washout, and locations of concentrated stormwater are all
noted on the PPP. Borrow and stockpile areas are not noted since the stockpiles exist on site and will be
moved first thing. They are shown on the E&SC plans, though.
2. Show possible stockpile/waste areas with silt fence around it.
RESPONSE: This site has existing stockpiles with almost all of the fill that will be needed for the
912 E. High St. Charlottesville, VA 22902 1434.227.5140 1 shimp-engineering.com
site. The PPP plan shows a later phase of the plans, when stockpiles will have already been used to fill
that back parking area where ST2 is.
3. Provide detail of concrete washout on the plans or with PPP.
RESPONSE: A concrete washout detail is now provided on the PPP.
D. Stormwater Management Plan (SWMP)
VSMP Re,; lion 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. Sheet 3: provide deed book/page of existing SWF easement (ex. 48" detention pipe).
RESPONSE: No easement exists. These pipes were put in before this was a requirement.
2. Sheet 4: Show proposed SWM facility & access easement for the pond.
RESPONSE: The SWM easements for the pond and for access to the pond are now included on
the plans.
3. Sheet 10:
a. Show the HGL in the profiles, LD-347 calcs or equivalent.
RESPONSE: Hydraulic grade lines are now shown on the profiles.
b. Show the 2, 10, & 100 yr design WSE lines for the basin.
RESPONSE: The water surface elevations for the various storms are now shown on the
detention pond profile.
c. Provide 2' minimum cover height over pipes.
RESPONSE: The pipe manufacturer specifications have a minimum cover of 1 foot in traffic
applications. I have attached the specifications for your reference.
d. Reduce outlet velocity to under 10 fps at F 1 end.
RESPONSE: The outlet velocity is now 9.7 fps at F 1 end.
e. Provide endwall at F1 end.
RESPONSE: An end section is now specified, ES-1. This is a much cheaper option and still
and acceptable practice.
f LD-229 design table — Provide pipe diameter in inches under column 14.
RESPONSE: Thank you, this has been updated to show diameter in inches rather than feet.
4. Detention basin:
a. Provide a sediment forebay. Follow the erosion & flood control guidelines from VADEQ,
Appx. D.
RESPONSE: In the guidelines referenced, a sediment forebay is required for BMPs. The
proposed detention pond is just a dry pond with no water quality treatment. I see instances where a
forebay would be desirable and cost effective, but in this instance the pond is small and easily accessible
for maintenance.
b. Design a low -flow, smaller diameter orifice(s) in riser structure before considering larger
diameter.
912 E. High St. Charlottesville, VA 22902 1434.227.5140 1 shimp-engineering.com
RESPONSE: The orifice has been changed from 12" to 8". A smaller orifice would require
a larger detention pond to still meet water quantity calculations (energy balance) while containing the 100
year storm. Due to site constraints of surrounding preserved slopes, parking lot, and floodplain, the pond
cannot be expanded further.
c. Show detail of trash rack.
RESPONSE: A trash rack detail is now provided on the stone details sheet.
5. Provide storm inlet drainage map.
RESPONSE: A storm inlet drainage map is now included on Sheet C14.
6. SWM Calcs — Please correct the diameter of outlet device # 1 showing 24.0" culvert. The plans
show a 30" culvert.
RESPONSE: The stormwater calculations have been updated to show a 30" outlet diameter.
7. Show letter of availability from the nutrient credit bank or provider on the plans. Currently, 2.49
lb/yr TP credit required.
RESPONSE: The VRRM has been updated showing the added impervious area from required
upgrades to the entrances. Nutrient credit requirements are now 2.59 lb/yr and a letter of availability is
included with this submission.
8. Contact Ana Kilmer regarding the Nutrient Credit Agreement.
RESPONSE: Acknowledged.
9. Record the SWM maintenance agreement.
RESPONSE: Acknowledged. To be completed at a later time.
E. Erosion and Sediment Control Plan (ESCP)
Virginia Code Sec. 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 plan content
requirements can be found in County Code section 17-402.
1. Sediment trap (ST2) will not be allowed on top of fill material or be held up by retaining wall
(policy).
RESPONSE: Acknowledged. The sediment trap has been relocated such that it is no longer
located in fill material.
2. Show the key symbols in addition to linetype symbols (i.e. SF).
RESPONSE: Symbols have been added in locations where erosion and sediment control items are
proposed.
3. Include CE in your LOD.
RESPONSE: The alternate CE is now included in the LOD.
4. Show/Provide RWD to sediment trapping device for each construction entrance.
RESPONSE: RWD to silt fence is now shown at the construction entrances to keep sediment
from being released to Route 250.
912 E. High St. Charlottesville, VA 22902 1434.227.5140 1 shimp-engineering.com
5. Sheet 7:
a. DD is needed to direct runoff to ST2.
RESPONSE: The trap location has been updated and diversion dikes are shown to direct
runoff to ST2 in all applicable phases.
b. SF needed along here (see comments for picture): May need additional offsite construction
easement to tie into grade. Letter of permission from offsite owner will suffice for this
review.
RESPONSE: The construction on the adjacent site proposed grading of the hillside on this
site, which they had a grading easement for. We are just tying into the proposed grade from that site plan.
I have now included the linework for the adjacent site on the VSMP sheets so you can see the grading tie
in. This does not require offsite work. Silt fence has been added in the location shown.
c. In the Sequence of Construction clarify that A5a end will be blocked for the new pipe until
the downstream detention pond grading is complete.
RESPONSE: We do not intend for A5a to be blocked during construction. Water from the
existing parking lot area will need to drain out. A note has been added to phase 3 of the plans for the
existing rip rap ditch to remain during the construction of the pond to divert water around the pond.
6. Sheet 8/10:
a. Provide a detail of what this IP looks like and refer to that detail (see comments for
picture).
RESPONSE: This special inlet protection is no longer needed and has been removed from
the plans.
b. Add OP to Al & F1 end and/or show that existing riprap is adequate. The OP riprap will
need to be sized and extend along length, La. A filter fabric should be placed underneath
the riprap.
RESPONSE: Outlet protection is now shown at the correct size. A detail is included on the
E&SC Details sheet showing the required length, width, depth, class, and filter cloth.
7. Sheet 9:
a. Add in noted items here: (see comments for picture)
RESPONSE: I have added notes to clarify which slopes are 2:1 or 3:1, needing ground cover.
The slopes you are referring to in this picture are already proposed from the Pantops Comer
Site next door and will not actually be disturbed during construction.
b. Add in low maintenance cover here & where needed.
RESPONSE: Notes for low maintenance ground cover have been added to the specified
areas from your picture.
If you have any questions or concerns about these revisions, please feel free to contact me at
kendra@shimp-en ing eering com or by phone at 434-227-5140.
Regards,
Kendra Patrick, EIT
Shimp Engineering, P.C.
912 E. High St. Charlottesville, VA 22902 1434.227.5140 1 shimp-engineering.com