SW6231203_Response To Comments_20240412

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Booth & Associates
April 12, 2024
VIA ONLINE LINK
Brianna Holland
Environmental Engineer
DEMLR Post-Construction Stormwater Program
512 N. Salisbury Street, Office 640E
Raleigh, NC 27604
Phone: [phone]
Email: postconstructiondeq.nc.gov
Subject: Response to NCDEQ Comments Dated March 14, 2024
Stormwater Project No. SW6231203
Gillespie— B1.9 Solar Utility Station
Cumberland County
Dear Ms. Holland:
Please find below a point-by-point response to your comments dated March 14, 2024, concerning
Gillespie— B1.9 Solar Utility Station (Stormwater Project No. SW6231203). Please find our responses
below in blue.
1. If you would like the solar panel surface areas to be considered pervious, you must
demonstrate compliance with recommendations 1-6 in Part E-6 of the Stormwater Design
Manual. You should discuss each of these items in the project narrative:
a. Recommendations 1, 3, & 4 — Please provide a note on the plans to avoid the
concentration of stormwater runoff, and to minimize the use of herbicides and
fertilizers.
• Please provide a note on the plans stating that the subsoils should not be
compacted during the installation of the solar panels. If the soils will be compacted,
then place a note on the plans stating that the soils should be tilled/amended so
that they can be returned to their pre-compaction condition (Solar Panel
Recommendation 1).
Recommendation 1: Notes were added to sheets CG201 and CG202 of the
drawing set stating subsoils on site will not be compacted during the installation of
solar panels, and if they are compacted, they are to be tilled and amended to
return the soil to its pre-construction condition.
Recommendation 3: The concentration of stormwater is avoided by grading the
solar array area and a uniform slope is provided to the greatest extent practicable.
See sheet CG102 for final post-construction conditions and CG301 for a slope
map.
Recommendation 4: Notes were added to sheets CG201 and CG202 of the
drawing set stating weed control and vegetation management shall be done
mechanically by mowing to avoid the use of herbicides and fertilizers.
2300 Rexwoods Drive, Ste. 300 919.851.8770 office
Raleigh, NC 27607 919.859.5918 facsimile
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Brianna Holland
April 12, 2024
Page 2
b. Recommendations 2 & 6— Please provide a detail on the main set of plans for the solar
panels showing that a sufficient horizontal disconnection length (at least as wide as the
solar panel) is being maintained between the rows of panels and that the vertical clearance
of the panels is less than or equal to 10 feet.
• Please also provide a slope map for the panel area so that the ground slope can be
determined. Indicate any slopes in excess of 8°/0 (Solar Farms Recommendation 2).
If there are any areas in the vicinity of the proposed solar panels that have a ground
slope in excess of 8% please provide some means of maintaining sheet flow.
Recommendation 2: The solar array area has been graded so it is entirely on slopes
less than 8%, this is reflected on sheet CG301 of the drawing set.
Recommendation 6: A detail of the solar array racks has been added to sheet
CG503 of the drawing set. The lowest vertical clearance or the "low-side" of the rack
shall not exceed 10' and will be a typical 3'.
• Please provide proposed contours on the main set of plans (Section VI, 8k). It is
recommended to provide a plan sheet demonstrating the final proposed conditions
of the site, excluding temporary erosion control methods.
Sheet CG102 shows the site plan in its finalized post-construction conditions.
Permanent proposed contours are shown and labeled.
c. Recommendation 5 — Please ensure that the proposed grasses to be planted under the
solar panels are a mix of warm & cool season grasses (Solar Panel Recommendation 5).
Permanent seeding mixture has been updated to include cool season grass (White
Clover) and a warm season grass (Bahia grass), this change is reflected on sheet CG202
and sheet CG501 of the drawing set.
2. Please describe the nature of how stormwater will be treated on site in both Section IV, 1 of
the application and in the stormwater narrative (Section VI, 5). This description/narrative
should expound on the low-density requirements for solar farms as outlined in Part E-6 of the
Manual.
Section IV, 1 of the state stormwater application and the narrative in the Stormwater
Management Report— Design Approach section have been updated to describe the post-
stormwater treatment and the low-density requirements for solar farms as outlined in Part E-6
of the NCDEQ Stormwater Design Manual.
3. Please provide design calculations showing how the built upon area associated with the solar
panel footings/foundations is determined (Section VI, 7). While the panels of the solar arrays
themselves can be considered pervious if designed in accordance with Part E- 6 of the
Stormwater Design Manual, the footings, supports, foundations, and any other related BUA are
still considered BUA and should be accounted for as such. Please ensure that the calculations
show that these associated BUAs are being included in the BUA calculations.
An impervious area table has been added to sheet CG300 that shows a break down of the
BUA. The solar arrays are pole mounted and reflect a minimal BUA. The State Stormwater
Application and Supplement-EZ have been modified to reflect this; impervious values have
been altered somewhat after reassessment from doing the BUA breakdown, but the project still
complies with low density specifications.
4. Please clearly identify and dimension all BUA in the main set of plans (Section VI, 8j). It is
noted that certain dimensions are included, but there does not appear to have enough
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Brianna Holland
April 12, 2024
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information to verify the BUA amounts. You may wish to add dimensioning to these areas,
callouts indicating the square footage of these areas, or a BUA table (similar to the one in
Section IV, 10 of the Application) to the plans. NOTE: Gravel areas that are subject to
infrequent vehicular traffic (approximately twice a month or less) can be considered to not
meet the definition of BUA per Part A-4 of the Stormwater Design Manual
(https://deq.nc.gov/about/divisions/energy-mineral-and-land-
resources/stormwater/stormwater-program/stormwater-design).
a. Please provide details and quantities of the impervious solar panel footings and
inverter pad so that the provided impervious area calculations may be verified
(Section VI, 8j).
An impervious area table has been added to sheet CG300 that shows a breakdown of
the BUA. The solar arrays are pole mounted and reflect a minimal BUA. The State
Stormwater Application and Supplement-EZ has been modified to reflect this. The
proposed gravel areas while they meet the criteria for infrequent use have been
calculated as part of the BUA as a conservative measure.
5. Application
a. Since this project is a low-density project, the "drainage area" listed in Section VI, 10 of
the Application is the total project area (as shown in Section IV, 7).This is explained in
Section IV, 9 of the Application. Please revise the total, on-site, and off-site drainage
areas (since the drainage area is the project area, there is typically no off-site
component to the "drainage area").
The total, on-site, and off-site drainage areas in Section IV, 10 have been updated to
reflect the Total Project Area value in Section IV, 7 and to comply with Section IV, 9 of
the State Stormwater Application.
6. Supplement-EZ
a. When revising the Supplement-EZ, please click the "CLICK TO LOAD FORM" link on
all pages to generate the rest of this form. This spreadsheet uses Macros to generate
all of the needed pages based on the information entered into the cover page and
drainage area page. Please ensure that form is fully generated and complete. The
drainage areas page will need to be re-loaded and resubmitted with the page that is
generated. The "Disconnected Impervious Surfaces" Page will not need to be
resubmitted.
The Supplement-EZ form has been updated.
b. Cover Page, Line 20 —As the Disconnected Impervious Surface Secondary SCM is
not being utilized, please revise this line to be blank.
Line 20 on the Cover Page is now blank.
c. Drainage Areas Page, Line 4 - Since this is a low-density project and the entire site
drains to the same receiving water, there should only be one drainage area listed
(Section IV, 9). This drainage area is the property area.
Line 4 on the Drainage Areas Page now says 1.
7. O&M Form
a. Please revise the provided O&M Agreement. Select "Low Density" and "User
Defined SCM," and then load the forms.
The O&M agreement has been updated and "Low Density" and "User Defined
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April 12, 2024
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SCM" has been added per comments. This form has not yet been re-signed by the
Fayetteville Public Works Commission, but will be upon approval of the rest of the
documents in this permit application package.
Solar farms have additional operation and maintenance requirements when compared to a
"typical" low-density project. These requirements are outlined in Part E-6 of the Stormwater
Design Manual and can be incorporated into the O&M Agreement Form via a "User Defined
SCM." Examples of User Defined SCM Maintenance Requirements that have been
approved previously for Solar Farms have been attached at the end of this letter.
NOTE: It is recommended to get a second copy of this form signed & notarized for the
Applicant's records (it will be helpful when they go to record it with the Register of Deeds).
8. Per the provided USGS topographic map (clipped below), there appears to be additional
surface water located within the project area. All surface water that appears on the latest
USGS topographic map must be accounted for and depicted on the plans per 15A NCAC 02H
.1017 (10). Please do the following:
a. Please include the on-site surface water area in Section IV, 6 of the Application. This
information should also be included on Line 4 of the Cover Page of the Supplement-EZ
Form.
The shown on-site surface water is derived from a Water of the U.S. Delineation Report
performed by ECS Southeast, LLP dated August 21, 2023. The delineation report can be
found as on Exhibit 3.0 in the accompanying Stormwater Management Report. ECS's
findings show the surface waters present on site and wetlands in the surrounding areas.
Our understanding is that an on-site analysis would override what is shown on a USGS
topographic map and thus they remain unchanged on the drawing set.
However, to assume a conservative value, the entire boundary of ECS' surface waters
and wetlands are now included in the surface water calculation in Section IV, 6 of the
Application.
b. Please recalculate the total project area as shown in Section IV, 7 of the Application. This
information should also be updated on Line 2 of the Cover Page of the Supplement-EZ
Form, on Lines 5 & 6 of the Drainage Areas Page of the Supplement-EZ Form, and in the
table in Section IV, 10 of the Application.
The Total Project Area has been updated in Section IV, 7 of the Application per the
request in Item 8.a above. The Supplement-EZ form and the drawing set have been
updated as well.
c. Please recalculate the project percent impervious area as shown in Section IV, 8. This
information should also be updated on Line 18 of the Drainage Areas Page of the
Supplement-EZ Form and in the table in Section IV, 10 of the Application.
The project percent impervious areas have been updated and reflected in the drawing set
(sheet CG300), the Application, and the Supplement-EZ form.
d. Provide vegetated setbacks on the plans per 15A NCAC 02H .1017 (10).
Existing vegetation will be used as the vegetated setback/50' vegetated buffer. The
setback and dimension are shown on sheets CG102, CG200 - CG202 of the drawing set.
"`C�/` Booth&Associates
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Brianna Holland
April 12, 2024
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If you have any questions, comments, or concerns, please to not hesitate to contact Laura Harris, by
phone at 919-851-8770 or by email at laura.harrisbooth-assoc.com.
Sincerely,
BOOTH &ASSOCIATES, LLC
•
Laura Harris, P.E.
Project Engineer III — Team Lead
LRH/rea
cc:
Project Number: P.0574167.E.TE.8121
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