SW6110103_Response To Comments_20230127

AECOM
JSOC, SOF C4 Facility (LI66362) and Microgrid Installation & Integration
Responses to NCDEQ Request for Additional Information
27 January 2023
USACE Project No. PN97470
AECOM Project No. 60652522
Additional information was requested by NCDEQ State Stormwater Engineer Jim Farkas, in a letter dated
January 12, 2023. The original comments are enumerated below with AECOM responses below each comment.
Tease ensure that the proposed SCM is sized/designed based on the actual drainage area to the SCM.
Per 15A NCAC 02H .1003(3)(b), any off -site or existing BUA that is not bypassed around the SCM must
be accounted for in the sizing of the SCM. For example, based on the provided information for the
proposed bioretention cell, the drainage area to the SCM is approximately 0.54 ac and contains about
16,443 sf of BUA (from DAs A.1 & A. 2, including existing BUA). This is different than the drainage area
of approximately 0.61 ac and BUA of approximately 0.28 ac for this SCM that is shown in the Application
and Supplement-EZ Form. Please revise as needed.
AECOM Response: The actual drainage area for the bioretention SCM is 0.54 acres (23,647 sf)
with 0.40 acres (17,466 sf) impervious (existing and new BUA). The Application and Supplement-
EZ Form have been revised accordingly.
2. Please clearly delineate the drainage areas to the SCMs in the main set of plans. This item is required
per 15A NCAC 02H .1042(2)(g)(iv). It is noted that the drainage area to the downstream culvert is shown
in the plans, however, the drainage area to each individual SCM must be shown in the plans. NOTE: An
off -site component of an SCM drainage area is an area that drains to the SCM but is located outside of
the project area. For example, drainage area A.3 would not be considered an off -site part of the
drainage area to the proposed bioretention cell since it does not drain to it. Any areas like drainage area
A.3 would be accounted for in the "Entire Site" column on the Drainage Areas Page of the Supplement-
EZ Form.
AECOM Response: Drainage Area 1 of the existing permit for the underground infiltration trench
SCM is shown on sheets C-901 and C-902. Drainage Area 2, which is part of the permit
modification for the bioretention SCM, is shown on sheet C-902.
3. mease prov►ae Tne ex►snng grouna surface eievanon Tor Tne simVit i poring (biorerennon cell MDC 1). It
is noted that the depth from the existing ground surface elevation to the SHWT (or in this case, the lack
of SHWT indicators) is provided, however, without the existing ground surface elevation for this boring,
we cannot determine the elevation of the SHWT and cannot verify adequate separation between the
bottom of the bioretention cell and the SHWT.
AECOM Response: Boring B-02 is shown on sheet CD101 and has an approximate ground
elevation of 268.2 feet. Based on geotechnical report, no SHWT was detected. The boring was
taken to a depth of 13 feet (i.e. elevation 255.2) without encountering SHWT. Consequently, the
SHWT elevation was entered as 255.2 feet on the Bioretention tab of the Supplement-EZ form,
which is about 4.8 feet below the bottom of bioretention (260.0 feet). This information is included
in the additional information section of the Bioretention worksheet.
4. Plan sheet CG501 has callouts indicating the presence of outlet protection for the inlet into the
bioretention cell and outlet out of the bioretention cell but the plans do not indicate the presence of outlet
protection and the sizing calculations for outlet protection were not provided. If outlet protection is not
needed, please remove the references to outlet protection from the plans and indicate that calculated
flows are nonerosive in the calculations. If outlet protection is needed, please show it on the plans and
provide the sizing calculations. This item is required per General MDC 4.
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AECOM
JSOC, SOF C4 Facility (LI66362) and Microgrid Installation & Integration
Responses to NCDEQ Request for Additional Information
27 January 2023
USACE Project No. PN97470
AECOM Project No. 60652522
AECOM Response: Outlet protection schedule for OP-1 and OP-2 are on detail sheet CE505.
Calculations have been updated to include OP charts and calculations.
5. VVIIIIC I/UI IC(.IUIICd, It IS IIUICU UICII IJUI/Ullly III UIC UlU/CICIIUUII GCII mi, IJacn up Into tIIC ylass svvalc
during design storms and will nearly overtop the adjacent roadway during larger storm events (see
attached). It is strongly recommended to either design the SCM to be off-line (so that larger storm events
are bypassed before entering the SCM) or to include an emergency spillway to prevent structural failure
of the roadway and embankment during large storm events.
AECOM Response: The outlet control structure has been revised to lower the maximum water
surface elevation of the 10- and 100-year design storms so that the access drive is not
temporarily inundated during these design storm events.
6. Please correct the following issues with the Supplement-EZ Form:
a. Cover Page:
Line 7 — Please include this item (15A NCA C 02H .1003(4) & .1017(10)). It is noted that
there are no surface waters located on -site, however, we ask that this information be
included. Lines 8 & 9 can be left as "N/a" since there are no surface waters located on -
site.
AECOM Response: There is approximately 30 feet of vegetation from the new SCM
outfall to the edge of the site. The USGS Topo Map shows the nearest surface
water (intermittent stream) at least 400 feet from the railroad culvert. Line 7 on the
Cover Page of the Supplement-EZ form has been revised to 30 feet.
b. Drainage Areas Page:
Entire Site Column:
The entire site column is an accounting of the entire project area, not just a sum of
the other columns. Any BUA located within the project area (whether or not it drains
to an SCM) should be accounted for in this column and the "drainage area" for the
entire site column is equal to the project area. While not required, you can add
bypass or "Site I" & "Site 2" columns to help clarify things if you wish (The
information provided in the calculations was very through and well put together,
unlike our forms). If the form is unclear, please let me know, we can set up a
meeting to discuss.
AECOM Response: The entire site column is revised. We calculated the total
project area for the permit modification to be 3.38 acres, consisting of 2.49
acres (original permit) + 0.61 acres (SITE 1) + 0.31 acres (SITE 2) — overlaps of
SITE 2 fuel utility trench with "Drainage Area 1" in the original permit.
Additional columns were added in an attempt to make the modification
changes clearer.
2. I i- a & 19-21 are not required for the entire site column.
AECOM Response: Noted and revised.
ii. Please revise the other columns as needed.
AECOM Response: Noted and revised.
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AECOM
JSOC, SOF C4 Facility (1-I66362) and Microgrid Installation & Integration
Responses to NCDEQ Request for Additional Information
27 January 2023
USACE Project No. PN97470
AECOM Project No. 60652522
c. Bioretention Cell Page:
i. Line 2 — Please revise as needed. This value should be calculated based on the actual
drainage area to the SCM.
AECOM Response: Bioretention has been revised to reflect the actual contributing
drainage area of 0.54 acres.
ii. Line 12 — Please clarify this point in the Additional Information (Line 44). Typically, projects
require this item, but since this project is located at Ft. Bragg, it is not required.
AECOM Response: Additional information is provided on Line 44 stating that
easements are not required since the project is located within Fort Bragg.
iii. Line 18 — Revise if needec
AECOM Response: See response to comment #3.
iv. Lines 34 & 3, here is an error in the Manual with regard to the mix percentages.
Please refer to 15A NCAC 02H .1052(6)(b)&(c). NOTE: The mix percentages appear to be
correct on the plans.
AECOM Response: Mix percentages are revised.
Line 36 — Please clarify/elaborate on this in the Additional Information (Line 44).
AECOM Response: Additional information regarding organic material in
"Engineered Fill" was added.
d. NOTE: The L)ww c uppiemenr rorm is nor requirea.
AECOM Response: Concur. The form is removed from Attachment B.
Provide PDFs of all rt„,sions, 2 hardcopie. _.. _ plan sheets, 1 harp,._,-, of other documents, and
a response to comments letter briefly describing how the comments have been addressed.
a. PDFs must be uploaded using the form at: hitps://edocs.deg,nc.gov/Forms/SW-Supplemental-
Upload
b. b. Hard copies must be mailed or delivered to the following address:
i. For FedEVUPS:
Jim Farkas
512 N. Salisbury Street, Office 640M
Raleigh, NC 27604
ii. For LISPS:
Jim Farkas
1612 Mail Service Center
Raleigh, NC 27699-1612
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AECOM
JSOC, SOF C4 Facility (1-I66362) and Microgrid Installation & Integration
Responses to NCDEQ Request for Additional Information
27 January 2023
USACE Project No. PN97470
AECOM Project No. 60652522
............—,;iivery:
Please reach out to me prior to hand delivering a submission to make sure that I (or someone
else in my group) will be able to receive the submission. Do not leave the package in the
foyer with the security guard. NOTE: Hard copies should not be sent to a Regional Office.
Doing so will delay the review process and the submission package may be lost while being
.cant frnm tha Raninnal nmra to ma in tha rantral nff;rn
AECOM Response: Noted. Revised PDFs will be uploaded with hard copies following.
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