HomeMy WebLinkAboutWPO202200005 Action Letter 2022-07-21SHIMP ENGINEERING, P.C.
Design Focused Engineering
July 21, 2022
David James
County of Albemarle Community Development
401 McIntire Rd, North Wing
Charlottesville, VA 22902
RE: Response Letter #3 for WPO202200005 Castalia Farm Winery
Dear David,
Thank you for your review of the VSMP plan for Castalia Farm — New Facility. This letter contains
responses to comments dated July 14, 2022.Our responses are as follows:
A. Stormwater Pollution Prevention Plan (SWPPP)
1. Addressed.
2. Registration statement: The start date should be changed. (Rev. 2) Acknowledged. Please include
and submit with SWPPP/
RESPONSE: The start date has been updated and the registration statement has been included
with the SWPPP.
B. Pollution Prevention Plan (PPP)
1. Addressed.
C. Stormwater Management Plan (SWMP)
1. Addressed.
2. Addressed.
3. Addressed.
4. Addressed.
5. Bioretentions: (Ensure bioretention meets all requirements per DEQ specifications:
https:Hswbmpvwrre.wp.prod.es. cloud.vt.edu/wp-content/uploads/2017/ 11 BMP-Spec-No-
9_BIORETENTION_v 1-9_03012011.pdf )
a. Addressed
b. Addressed
c. Addressed
d. Acknowledged.
e. Addressed
912 E. High Sr. Charlottesville, VA 22902 1434.227.5140 1 shimp-engineering.com
f. Addressed.
g. Addressed.
h. Addressed
i. (Rev.1) Provide infiltration rate of V2 in/hr in order to remove underdrain requirement.
RESPONSE:
L Underdrain has been added to bioretention basins 1 and 2 in lieu of infiltration.
6. Addressed.
7. Addressed.
8. Addressed.
9. Addressed
10. Coordinate nutrient credit agreement with Ana prior to purchase. Purchase of credits 'A i l I be
needed prior to bond request. (Rev.'/z) Acknowledged — Currently 1.64 TP credits nc
Response: We will be dedicating open space in lieu of purchasing nutrient credits. As shown in
the revised VRRM calculations, the open space dedication and treatment provided by the
biofilters provides all of the reduction required. This has been updated in the swm talc packet and
the narrative on sheet C8 as well.
11. Addressed
12. Addressed
13. Addressed
14. Acknowledged
15. Addressed
16. (Rev. 2) Record SWM Maintenance Agreement
Response: This will be recorded prior to plan approval. Please provide an agreement for us to
complete.
D. Mitigation Plan (MP)
1. Addressed.
2. Addressed.
3. Acknowledged.
4. Addressed
5. Addressed.
6. Addressed
912 E. High St.. Charlottesville, VA 22902 1434.227.51401 shlmp-engineenrig.rom
7. Addressed
8. (Rev. 1) Provide mitigation to stream buffer areas first and foremost, then, provide to areas
outside of stream buffer. Areas outside of buffer will need to be shown in a mitigation or
conservation easement.
RESPONSE: The mitigation plan has been revised to only include areas within the stream buffer.
Per the revised plan, the required area will be cleared of dead trees and invasive species as
directed by a certified arborist.
E. Erosion and Sediment Control Plan (ESCP)
1. Addressed.
2. Acknowledged.
3. SheetC10/11
a. Show existing drainage divides.
b. Addressed.
c. Addressed.
d. Addressed.
e. Addressed
f. Ensure channel diversion directional change is not too severe & greater than 90 degrees.
Energy dissipation check dams can be implemented. (Rev.1/2) Partially addressed. This
area needs to be corrected for a number of reasons.
g. (Rev. 1) RWD should be shown on E&S ph2 instead once the access is graded. (Rev 2.)
Not addressed,
h. (Rev. 1) Show a staging and stockpile location. Show SF around the stockpile. (Rev. 2)
Not addressed.
i. i. (Rev. 1) Provide the channel design for the diversions as well, including CWD. Show
the drainage area maps, cross-section dimensions, 2-yr & 10-yr WSE, and appropriate
liner type needed. (Rev. 2) Not addressed.
j. (Rev. 1) ST #4 detail needed? (Rev. 2) Not addressed.
RESPONSE:
a. Existing drainage divides are now shown on sheet C3.
f. The severity of directional change has been reduced and check dams have been added to
slow water exiting the diversions where outlet protection is not already provided. The clean
water diversion at this location has also been shifted to correctly follow existing grade and
will be installed per the ditch calculations on C 16.
g. The RWD is now shown on Phase 2.
h. A staging/stockpile area is now shown and protected by silt fence.
i. Channel design for all ditches and diversions have been calculated. The diversion detail
now shows max WSE and the required depth and liner. E&S diversions located along future
permanent ditch locations and should be designed per the calculations on sheet C 16. For
simplicity, the most conversative design was used for CWD and RWD typical details when
not located at a permanent ditch location.
j. A detail for ST 4 is now included.
4. Sheet C 12, etc. -
a. Conversion to permanent facilityBMP shall not occur until the road and all upstream
drainage areas are fully stabilized. This would be after #12 in the phase 2 sequence.
912 E. High St.. Charlottesville, VA 22902 1434.227.51401 shlmp-engineenrig.rom
(Rev.1) Clarify and label SWM facilities. Conversion to bioretention shall not happen
until all upstream areas are fully stabilized. You can provide the grading necessary, but it
will still function as a trap must meet volume requirements and must be cleaned out prior
to conversion. (Rev. 2) Partially addressed. Revise the sequence of construction to match
what you're stating.
b. Addressed.
RESPONSE:
a. The E&SC notes have been updated to clarify the transition from sediment traps to
bioretention basins. All upstream areas will be fully stabilized prior to conversion. This is
stated in the sequence of construction: "Install bioretention #1/2 once all upstream areas are
permanently stabilized." Sediment traps #1 and #2 should remain until bioretention basins #1
and #2 are complete as the basins are upstream of the sediment traps.
Sheet C12 should still be showing ESC sediment traps and not the permanent SWM features in place.
(Rev.1) SWM facilities should be only shown on SWM plan, unless protected and offline. (Rev. 2)
Partially addressed. Revise the sequence of construction to match what you're stating.
RESPONSE: Sediment traps are shown in phase 2 and are not removed until phase 3. The detention
pond grading is now removed from phase 2. Sediment trap 4 changes to be slightly larger during
phase 2 to allow for grading of the dam and upstream areas and is not fully converted until it is
protected.
6. Addressed.
7. (Rev.1) Sheets C3, C9-C12: Show all critical slopes (typ. shaded). Existing critical slopes are not to
be disturbed, unless a waiver or exemption has been granted. 18-4.2, 14-304. (Rev. 2) Per email — a
small hatch of critical slope is not shown.
RESPONSE: This critical slope is now shown. In order to avoid disturbing this area, the ditch was
rerouted.
8. (Rev.1) Sheet C4: Grading next to stream buffer appears to be in critical slopes but will need to
verify. Exception not allowed for drainageways if within. Provide alternate alignment. 18-4.2.6. (Rev.
2) Acknowledged, Will need to verify.
RESPONSE: See response to comment 7. Per email correspondence, critical slope adjacent to the
stream buffer was missing and is now shown. The ditch has been rerouted.
9. Addressed
10. Addressed
11. (Rev. 2) C3, etc: Please show the existing contour elevations.
RESPONSE: Existing contour elevations are now shown.
12. (Rev. 2) CI I-C14: Rc 11e appears to be F = 50'.
RESPONSE: The scale is F = 50' and was labeled incorrectly. This has been updated.
912 E. High St.. Charlottesville, VA 22902 1434.227.51401 shlmp-engineenrig.rom
If you have any questions or concerns about these revisions, please feel free to contact me at
chris@shimp-en ine eerine com or by phone at 434-227-5140.
Regards,
Chris Marshall, EIT
Staff Engineer
Shimp Engineering, P.C.
912 E. High St.. Charlottesville, VA 22902 1434.227.51401 shlmp-engineenrig.rom