SW6231109_Response To Comments_20240315

Dewberry Engineers Inc. 919.881.9939
Dewberry
2610 Wycliff Road, Suite 410 919.881.9923 fax
Raleigh, NC 27607 www.dewberry.com
March 14, 2024
Jim Farkas
State Stormwater Engineer
North Carolina Department of Environmental Quality
512 N. Salisbury Street, Office 640M
Raleigh, NC 27604
Reference: Duke Energy Progress, LLC
Barker Laydown Yard (SW6231109)
Cumberland County, NC
Stormwater Low Density Application
Dewberry Project No. 50130756
Dear Mr. Farkas:
Dewberry Engineers Inc. has responded to the comments in the email received from NCDEQ
dated 02/20/2024 as follows:
Discreoancies/Corrections:
Comment 1: Please include the on-site surface water delineation and vegetated setback delineation (as
requested in the 1112012024 email and required per 15A NCAC 02H.1042(2)(g)(iii)) or include a note on
the plans indicating that the on-site surface waters are located outside of the 9.1 acres of land to be
disturbed within the project area. Your response to comments indicating that there are no surface waters
located on-site is noted, however, the Application indicates that there are 18.25 ac of surface water and
the surface water is apparent on the USGS topo map/satellite imagery(Grays Creek&pond north of
Braxton Rd.). Please revise as needed to address this comment.
Response 1: Note 6 under General Site Plan Notes has been updated to indicate the on-site surface
waters are located outside of the 9.1 acres of land to be disturbed within the project area.
Comment 2: Please include the drainage area delineation to the vegetated conveyances in the main
set of plans (required per 15A NCA C 02H.1042(2)(g)(iv) and Section V1,8o of the Application). It is
noted that the drainage area map is included in the calculations (which was used for review), however
this needs to be provided in the main set of plans. Please revise as needed.
Response 2: Drainage area delineation sheet has been added to the set as sheet number 4.
Comment 3: Per the provided drainage area map, a third swale, PD 3 is shown, however the design of
this swale is not provided in the calculations or shown in the Supplement-EZ Form. Please revise as
needed.
Response 3: PD-3 will sheet flow off site to the north and naturally drain to Grays Creek through the
existing horse pasture and drainage easement. PD-3 has been renamed to DA-3 to indicate there is no
associated swale and the area is disconnected impervious that will filter through the horse pasture
before entering the drainage easement connected with Grays Creek.
Comment 4: When calculating the design flowrate for the swales, please either use a time of
concentration of 5 minutes or provide calculations showing how the time of concentration was determined.
Please revise as needed.
Response 4:The time of concentration has been changed to 5-min and the design for the ditches has
been changed to meet the 10-Yr storm event MDC for level spreaders. See the attached revised
calculations.
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Comment 5: Please clarify where the existing drop inlet that you are tying into ultimately outfalls and if the
system is sized to handle the additional proposed flow. Per 15A NCAC 02H.1003(4)(e), untreated
stormwater runoff cannot be discharged through a vegetated setback, but rather at the edge of the setback
and allowed to flow through the setback. Per 15A NCAC 02H.1003(5), stormwater outlets must be stable
during the 10-year storm event. Please revise as needed.
Response 5:The proposed yard inlet has been removed to meet low-density requirements and a level
spreader has been designed to allow water to sheet flow through a vegetative filter strip at the edge of
the project boundary.
Comment 6: Please correct the following issues with the Supplement-EZ Form:
o Cover Page:
• Line 2—Please use the project area (104.8 ac) instead of the property area (123.05 ac).
• Lines 7& 8—Please answer these items. These items refer to vegetated setbacks provided
from surface waters (any surface water indicated on a USGS topographic map, such as
Grays Creek). Please revise as needed to address this comment.
o Drainage Areas Page:
• Line 11— This item refers to BUA that is located outside of the 104.8 ac project area
(typically, this item is not used for low-density projects).
o Low-Density Page:
• Line 12— This item is required per 15A NCAC 02H.1003(4)(e). Please ensure that the
design meets this requirement.
• Slope Column—Please enter the values in this column as a percentage (a value of"0.01"
entered is 0.01% -0.0001 ftfft).
Response 6: Cover Page:Line 2 has been adjusted to reflect the project area of 104.8 acres rather than
the property area of 123.05. Lines 7 and 8 have not been adjusted. As noted in response 1, the on-site
surface waters are located outside of the 9.1 acres of land to be disturbed within the project area. The
nearest surface water(Greys Creek)to our LOD is about 700'to the north.
Drainage Area Page:Line 11 adjusted to N/A since not applicable for low-density projects.
Low-Density Page: Line 12 has not been adjusted. Per the above answer, the nearest surface water is
about 700'to the north, so no setbacks are required. The swale table has been updated to reflect the
new design and the slopes are correctly indicated as percent.
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Comment 7:2x signed &sealed hard copies of a plan sheet showing the following corrected additions:
• Surface water area delineation. This item is required per 15A NCAC 02H .1042(2)(g)(iii).
Please make this more clear on the plans.
• Vegetated setback from surface waters. This item is required per 15A NCAC 02H
.1042(2)(g) & Section VI, 8p of the Application. Vegetated setbacks are required from all
surface waters (more information can be found in 15A NCAC 02H .1003(4) & .1017(10)).
• If applicable, Grading plan that outlines proposed contours and drainage patterns. This item
is required by 15A NCAC 02H .1042(2)(g)((iv) &(v)).
• If applicable, BUA dimensions and layouts. This item is required per Section VI, 8j of the
Application. The BUA information shown in the Application, Supplement-EZ Form, and
calculations should be verified from the plans.
• Details of roads, sidewalks, drainage features, piped collection systems, and the proposed
stormwater controls. This item is required per Section VI 81 of the application.
Response 7: There is no surface water delineated on site. Note 6 under General Site Plan Notes has
been updated to indicate the on-site surface waters are located outside of the 9.1 acres of land to be
disturbed within the project area. Therefore, vegetative setback is not applicable to the project and has
been made clear on the plans.
A grading plan has been created ana added to the plan set as sheet 4 showing the proposed contours
for the gravel laydown yard as well as the ditch, berm, and level spreader. Items required per section VI
8j have been included in the revised submittal package.
Additional details for the level spreader and swale have been added to the detail sheet.
Dewberry Engineers Inc. has prepared a revised supplemental package for your review and
approval for the above referenced project, original package submitted on 11/17/2023. Included in
this submittal are:
• Two (2) copies of the revised plan sheets
• One (1) copy of the revised stormwater package with revised calculations and low-density
stormwater forms
• All revised documentation has also been uploaded electronically
Should you have any additional questions or concerns, please feel free to contact me via phone
[phone] or e-mail (zeuloadewberry.com).
Sincerely,
Dewberry Engineers Inc.
Zachary Eulo, P.E.
Project Manager
Enclosures
Cc: Nuwan Wijesuriya, Duke Energy Progress, LLC
" " Dewberry
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