HomeMy WebLinkAboutWPO202200005 Correspondence 2022-05-27SHIMP ENGINEERING, P.C.
Design Focused Engineering
May 27, 2022
David James
County of Albemarle Community Development
401 McIntire Rd, North Wing
Charlottesville, VA 22902
RE: Response Letter #2 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 May 19, 2022.Our responses are as follows:
A. Stormwater Pollution Prevention Plan (SWPPP)
1. Addressed.
2. Registration statement: The start date should be changed.
RESPONSE: The start date has been updated.
B. Pollution Prevention Plan (PPP)
1. Addressed.
C. Stormwater Management Plan (SWMP)
1. Addressed.
2. Addressed.
3. Addressed.
4. Det. Pond: Show number and spacing of barrel antiseep collars. (Rev. 1) Provide what the
residence time says regarding seepage through embankment? Show the 4:1 phreatic line from the
design high WSE, if it intersects the downstream slope seepage control required. See antiseep
collar design for spacing requirements.
RESPONSE: The phreatic line is shown in the graphic below based on the 10-yr WSE. The line
does not pass the toe of the embankment.
912 E. High Sr. Charlottesville, VA 22902 1434.227.5140 1 shimp-engineering.com
5. Bioretentions: (Ensure bioretention meets all requirements per DEQ specifications:
https:Hswbmpvwrrc.wp.prod.es. cloud.vt.edu/wp-content/uploads/2017/ 11 BMP-Spec-No-
9—BIORETENT10N_vl-9-0301201 1.pdf )
a. Ensure 2-ft minimum bottom to bedrock separation.
b. Ensure 2-ft minimum bottom to seasonal high water table separation.
c. Filter media: Please go with the 2011 standards on recommended bioretention soil mix
composition (Table 9.6). We have found that higher % of fines (clay content) have
caused issues with water filtrating though. (Rev.1) Not addressed —Replace table 9.7
shown on sheet C7.
d. Acknowledged.
e. Acknowledged, pending test results.
f. Addressed.
g. Addressed.
h. Provide that the pretreatment SOD is approved as an acceptable form. (Rev.1)
Show/verify that the pre-treatment cell is at least 15% of the total treatment volume
(inclusive). Show dam or berm before entering biorientation are, sec. 6.4.
i. (Rev.1) Provide infiltration rate of S4 in/hr in order to remove underdrain requirement.
RESPONSE: a. Soil testing will be performed to confirm bedrock separation. A supplemental
report will be provided. b. Soil testing will be performed to confirm high water table
separation. A supplemental report will be provided. c. Table 9.7 has been replaced with Table
9.6 from the 2011 standards. h. The pretreatment sod is included in the BMP design standards
as an acceptable form. The BMP design table has been included on sheet C 16 which allows
for grass filter strips. A berm is now shown between the pretreatment area and the
bioretention basins. Pretreatment volume is calculated and shown in the design tables for
each basin as 15% of the treatment volume. L An infiltration test and report will be provided.
6. Addressed.
7. Addressed.
8. Addressed.
912 E. High St.. Charlottesville, VA 22902 1434.227.51401 shlmp-engineenrig.rom
9. Provide letter of availability from nutrient source provider. 0.91 TP credits currently required
according to VRRM.
RESPONSE: A letter of availability is now included.
10. Acknowledged.
11. (Rev.1) Sheet CT
a. Verify top of weir.
b. Filter media depth needs to be 4' where trees are proposed.
RESPONSE: a. Top of weir elevation has been corrected in profile. b. A note has been added that
locations with trees shall have 4' of filter media.
12. (Rev.1) Sheet C 16: Add note for bioretention tree planting area filter media to be composed of
50/30/20 ratio mix per sec. 6.6.
RESPONSE: A note has been added specifying the desired filter media mix.
13. (Rev.1) Please use the new development VRRM. I don't consider this a prior development
because the land is agriculture, nor are impervious areas (0.27ac pre-dev) being altered (if any).
RESPONSE: The new VRRM spreadsheet is now being used. There is no change to nutrient
treatment requirements.
14. (Rev.1) According to VRRM there are 0.55ac of Forest/Open space that will need to be protected
post -development. This area will need to be shown and called out as Forest & Open Space in an
easement on the plans.
RESPONSE: Acknowledged, this will be reflected on the easement plat.
15. (Rev.1) Add note to Cover Sheet: "The SWM Forest and Open Space Easement is subject to the
guidance set forth by DEQ in the Virginia Stormwater Management Program. The areas will
remain undisturbed in a natural, vegetated state, except for activities as approved by the local
program authority, such as forest management, control of invasive species, replanting and
revegetating, passive recreation (e.g., trails), and limited bush hogging to maintain desired
vegetative community (but no more than four times a year)."
RESPONSE: This note has been added to the cover page.
D. Mitigation Plan (MP)
1. Addressed.
2. Addressed.
3. Acknowledged.
4. The stream crossing shall not disturb more than 30 1-ft. It appears you exceed this amount at the
second crossing.
RESPONSE: The road has been adjusted to more directly cross the stream, limiting the total
disturbance within the stream buffer. Disturbance may exceed 30' for fill slopes. The total fill has
been reduced with a more optimal slope in order to limit the extent of the fill slope. A maximum
10% slope is now used leading up to the stream buffer crossing to decrease the slope over the low
point of the stream, limiting the overall fill.
912 E. High St.. Charlottesville, VA 22902 1434.227.51401 shlmp-engineering.rom
5. Addressed.
6. Provide copy of approved permit from USACE for the stream crossings. (Rev.1) Acknowledged.
I would need some sort of confirmation from USACE that permitting is not required.
RESPONSE: Verification will be provided. USACE has been contacted to confirm permit
coverage.
7. Show the design for a single stream crossing. Provide justification for two stream crossings. [17-
604 C1 [ 17-406 A.31. (Rev.1) It's the access road (# of crossings) to be able to use the lot. The
proposed parking is not in violation of Zoning ordinance and it was determined the access road is
allowed.
RESPONSE: Acknowledged.
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: Disturbed area within the stream buffer was selected for mitigation first. The
mitigation areas are shown as turf and not as protected open space so a conservation easement is
not required.
E. Erosion and Sediment Control Plan (ESCP)
1. Addressed.
2. Acknowledged.
3. Sheet C 10/11—
a. Show existing drainage divides.
b. Addressed.
c. Addressed.
d. Addressed.
e. Show drainage area to diversions (5ac max).(Rev.1) Acknowledged, Update the legend
key for DV & remove DD.
f. Ensure channel diversion directional change is not too severe & greater than 90 degrees.
Energy dissipation check dams can be implemented. (Rev.1) Partially addressed. This
area needs to be corrected for a number of reasons.
RESPONSE: e. The legend has been updated on all E&SC sheets to reference DV instead of
DD. E 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.
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.
(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.
b. Acknowledged; see 10.b.
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.
912 E. High St.. Charlottesville, VA 22902 1434.227.51401 shlmp-engineenrig.rom
Only sediment trap #3 is located within the footprint of a bioretention basin. Sediment traps
# 1 and #2 should remain until bioretention basins # 1 and #2 are complete as the basins are
upstream of the sediment traps.
5. Sheet C 12 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.
RESPONSE: SWM facilities are shown in the third phase of the E&SC plan when all upstream
areas are stabilized. The E&SC narrative has been revised to clarify the transition from sediment
traps to bioretention basins.
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
RESPONSE: Critical slopes are now shown but are not within the limits of disturbance.
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
RESPONSE: The current design does not disturb any critical slopes.
9. (Rev.1) Sheets C11-14: Please label or callout the sediment traps, bioretentions, and basins for ease
of identification and to follow construction sequence (ST# 1, Basin #3, etc).
RESPONSE: Labels are now shown.
10. (Rev.1) Sheets C11/12
a. Reduce grading to under 2:1
b. Show TS/PS & MU for constructed slopes adjacent to road ditches.
RESPONSE: a. Grading does not exceed 2:1 slope. b. TS/PS/MU is now shown for all constructed
slopes.
If you have any questions or concerns about these revisions, please feel free to contact me at
chris@shimp-en ing eering 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
912 E. High St.. Charlottesville, VA 22902 1434.227.51401 shlmp-engineenrig.rom