HomeMy WebLinkAboutWPO202000028 Correspondence 2020-08-05 (2)SHIMP ENGINEERING, P.C.
Design Focused Engineering
August 3, 2020
David James
County of Albemarle
Department of Community Development
401 McIntire Road, North Wing
Charlottesville, Virginia 22902
RE: Response Letter #1 for WPO202000028 Regents School of Charlottesville
Dear David,
Thank you for your review of the VSMP plan for Regents School of Charlottesville. This letter contains
responses to County comments dated June 23, 2020. Our responses are as follows:
A. General
1. Show off -site disturbance in an easement. Record with plat.
RESPONSE: Off -site disturbance for the road is shown in an easement. The plat will be recorded
prior to approval. The pedestrian path to the Church parking lot will be in an easement, the
location is to be finalized soon.
2. Submit a floodplain development permit for proposed disturbance in the floodplain.
RESPONSE: Acknowledged. A floodplain development permit has been submitted.
3. Submit a mitigation plan for proposed disturbance in the stream buffer.
RESPONSE: Mitigation planting is now specified on Sheet C 11.
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 ESCP, (3) a SWMP, and (4) any TMDL measures necessary.
1. You'll need to update Section 5. See comment D.I.
RESPONSE: Section 5 has been updated.
2. Complete Section 9 prior to approval.
RESPONSE: Acknowledged. To be completed with final SWPPP.
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 and concrete washout locations are now shown. Stockpile locations are
shown on the E&SC plan, but the PPP does not include all phases of the plan.
912 E. High St. Charlottesville, VA 22902 1434.227.5140 1 shimp-engineering.com
2. Show possible stockpile/waste areas with silt fence around it.
RESPONSE: This is shown on the E&SC plan, but the PPP does not include all phases of the
plan. The phase with the most information / detail is used for the PPP plan.
3. Provide detail of concrete washout on the plans or with PPP.
RESPONSE: Concrete washout detail is now included on the PPP.
D. 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. You're discharging into a natural channel/stream and therefore site runoff must satisfy Energy
Balance regardless if the 2 LOA criteria are met in 9VAC25-870-66.B.4.
RESPONSE: After the clarification from DEQ was received, we revised the plans and
calculations to show that the drainage area to Point of Analysis B, a natural channel, satisfies the energy
balance equation. However, Point of Analysis A is actually a manmade channel. Included in the
stormwater calculations packet is a picture from VDOT plans for I-64 ramps showing the relocation of the
stream in the area of POA A. Also included is an exhibit showing the current VSMP plans overlaid on
this VDOT picture so that the portion of channel at POA A can be verified as manmade.
2. Show letter of availability from the nutrient bank provider on the plans if you intend to purchase
credits. Currently, VRRM shows 2.84 lb/yr credits required.
RESPONSE: The VRRM has been updated and is now showing 2.65 Ib/yr credits required. This
difference is largely due to the shoulder widening along Reservoir Road — I originally thought it would be
paved but it is actually just a graded shoulder. A letter of availability is now provided on the plans.
3. Show Forest/Open Space protected in an easement. Submit an easement plat. Plat and deed will
need to be recorded prior to VSMP plan approval.
RESPONSE: A Forest/Open Space easement is now shown. An easement plat will be submitted
in the near future.
4. Please include these notes: (see comments)
RESPONSE: The referenced notes are now included on the cover sheet.
5. Provide inlet & ditch drainage area maps and determine appropriate liner for ditch needed (see
comments for picture).
RESPONSE: Inlet and ditch drainage area maps are now included. An EC-3 type 1 liner has been
added to the ditch by Reservoir Road.
6. Velocity is excessive at AO and BO outlets. Try to reduce below 10 fps. Also, add ES-1 at outlet
end.
RESPONSE: The velocity at BO was incorrect in the spreadsheet (the values from B2-B 1 must
have been duplicated). It is actually 5.9 fps. The pipe slope of Al -AO has been adjusted to lower the outlet
velocity at AO. An ES-1 has been added to each outlet pipe.
7. Provide HGL in profiles (LD-347).
912 E. High St. Charlottesville, VA 22902 1434.227.5140 1 shimp-engineering.com
RESPONSE: The HGL is now shown on the profiles.
8. Show roof drain connections. Provide sizing & inlet design for the `yard drains'. Show profiles &
point of connection (invert out) locations.
RESPONSE: We do not have exact downspout locations from the architect yet, but approximate
connection locations are now shown. A nyloplast grate inlet capacity chart is now included in the
stormwater calculations packet for sizing of the yard drains. Profiles of the roof drains are not included, as
these locations are subject to change. However, a minimum slope is now specified on C 12 to ensure they
will function as intended (all 10 yr flow rates to each roof drain pipe is < 1 cfs).
E. Erosion and Sediment Control Plan (ESCP)
Virginia Code Sec. 62.1-44.15:55 requires the VESCP authority to approve or disapprove an ESCR 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. Sheet 1: Designer to verify existing site conditions and topography are accurate. Provide date of
field verification — topography should be visually field verified within the last year.
RESPONSE: Topography has been field verified by Justin Shimp on multiple occasions, the
cover sheet now lists his field verification date of 10/22/2019.
2. Sheet 2: Show the floodplain.
RESPONSE: The floodplain is shown, though it is not visible on every sheet because of the scale.
More labels have been added so that the floodplain location can be seen more easily.
3. Sheet 3: Please show existing drainage divides.
RESPONSE: A predevelopment drainage area map is now included, showing existing drainage
divides.
4. Construction Entrance: Show location of sediment trapping device.
RESPONSE: Silt fence was added downstream of the CE in phase 1, the diversion dike in phase 2
was extended to transport water from the CE to ST2, and the curb will be in place in phase 3 to capture
water from the CE.
5. Sediment traps: The height, H (ft) are reported incorrect in the table on Sheet 14 and need to
match the height shown on the plans. See the width to height table below (see comments).
RESPONSE: The heights (H) have been corrected on the detail on Sheet 14. The outlet berm
width (Z) for ST3 has been increased to 4.5 ft, the others will remain the same.
6. ESC sheets (phase 2 & 3): Add DC symbols.
RESPONSE: Dust control symbols have been added to the parking lot area in phases 2 and 3.
7. Sheet 7: Add a diversion (DV) to ditch (see comments).
RESPONSE: DV symbol added to ditch near Reservoir Road. Details for the ditch are included in
the SCC section detail.
912 E. High St. Charlottesville, VA 22902 1434.227.5140 1 shimp-engineering.com
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
Shimp Engineering, P.C.
912 E. High St. Charlottesville, VA 22902 1434.227.5140 1 shimp-engineering.com