SW3240306_Response To Comments_20240701

June 28, 2024
Mr. Jim Farkas Via Email:Jim. Farkas(a deq.nc.gov
NCDEQ Stormwater
512 N. Salisbury St, Office 640E
Raleigh, NC 27604
Subject: Duke Energy — Lyle Creek Sw Station
Stormwater Permit — Disposition of Comments
Dear Mr. Farkas:
HDR is pleased to present this disposition of comments to NCDEQ pertaining to the comments
received on 6/18/24 via email. All comments have been addressed below, and updates were made
accordingly to the construction drawings, applications, and calculations.
1. Please upload the electronic files as indicated in the 3/21/2024 email (see below). Electronic
files are required per 15A NCAC 02H .1042(2).
Completed for first submittal (3/20/2024) and second submittal (6/28/2024).
2. As designed, there is an excessive amount of piping (pipe network in the vicinity of the
substation) for the project to be considered as low-density (see 15A NCAC 02H .1003(2)(c)).
Please either reduce the avoidable piping or permit the site as a high-density project. Please
revise as needed.
Plans have been updated to remove the excessive piping within the substation. The
site has been designed low-density based on the usage of vegetated conveyance in
all available locations. Within the project Limits of Disturbance (approx. 19.4 Acres),
1,900 linear feet of swale have been utilized. Total linear feet of swales (1,900 LF) is
majority use compared to the total linear feet of the piping/culverts (1,120 LF).
Per 15A NCAC 02H .1003(2)(c), Culvert/Piping has been utilized only when it cannot
be avoided. The piping within the electrical substation fencing is critical in order for
personnel to safely drive on the station access road inside the perimeter of the fence
and access equipment during an emergency event.
3. Please ensure that the ditch alongside the access road is included in the low-density swale
table in the Supplement-EZ Form.
Completed. Ditch has been included.
4. Please clearly indicate the required 30' wide vegetated setback from surface waters
(measured from the top of bank) in the main set of plans (required per 15A NCAC 02H
.1042(2)(g)(iii). See 15A NCAC 02H .1017(10).
Completed
hdrinc.com
440 S.Church Street,Suite 1200;Charlotte,NC 28202
T 704.338.6700 F 704.338.6760

Lyle Creek Sw — FYZ
Stormwater Permitmit—Disposition of Comments
Page 2 of 2
5. Please correct the following issues with the Supplement-EZ Form:
a. Cover Page: Completed
i. Line 4 — Include the surface water area (See Section IV,6 of the Application).
ii. Lines 7-9 —Answer these items (refers to setback from surface waters per
15A NCAC 02H .1017(10)).
b. Drainage Area Page: Completed
i. The information in this table should correspond to the information shown in
Section IV, 10 of the Application. Both column will be identical and will refer to
the entire project area (there are no off-site components to the project area).
Please revise as needed.
c. Low-Density Page: Completed, flows have been updated to reflect the design
storm intensites. V allowable has confirmed per Part C-11 of the Manual and
updated in the table.
i. Please note that when calculating the design flowrate for the swales, the 10-
year design storm (not necessarily the 10-year, 24-hour storm event) must be
used. The design storm intensity is determined by using the time of
concentration and provided IDF information from NOAA. Please revise as
needed (it is recommended to use the Rational Method for determining the
design flowrate for the swales).
ii. Please clarify where the Vallowable of 10 fps came from. Vallowable values
can be found in Part C-11 of the Manual or provided from another reliable
source. NOTE: Design parameters for the swales should reflect permanent
design conditions (not temporary E&SC conditions).
HDR appreciates the opportunity to work with NCDEQ to meet all permitting requirements and
expeditiously approve the permits required for the switching substation project. Please do not
hesitate to contact me at 980.337.5002 or Caroline.DeBruhl(@hdrinc.com.
Respectfully submitted,
fzI
HDR Engineering, Inc. of the Carolinas
Caroline N. DeBruhl, P.E.
Civil Engineer
cc: Joe Puckett, P.E. (HDR)
Glen Allen, P.E. (HDR)