SW6240705_Response To Comments_20241029

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October 29, 2024
Mr. Jacob Beeker
NCDEQ-DEML Post Construction Stormwater Program
512 N. Salisbury Street, Office 625Z
Raleigh, NC 27604
RE: Stormwater Permit No. SW6240705
Harnett County Northwest Convenience Center
Dear Mr. Beeker
We are in receipt of the Department's September 30, 2024 letter requesting additional information
on the above referenced stormwater permit application. The Department's comments are provided
below with our responses in italics for ease of review.
1. The most current version of the Application, which we received a hard copy of, could not be
found in the online repository. Please ensure that, upon next submission, all project documentation
is uploaded to the online repository, as required by 15A NCAC 02H .1042(2).
A revised Application Form is attached that reflects a high-density project is attached and has been
uploaded into the online repository.
2. Low Density Design
a. Per 15A NCAC 02H .1003(2)(c), a minimal amount of non-vegetated conveyances for
erosion protection shall be allowed only when it cannot be avoided. The provided plans appear
to propose a riprap-lined conveyance. Please provide documentation demonstrating that the
riprap lining cannot be avoided (in lieu of permanent vegetated stabilization, or an un-lined
channel)or remove the riprap lining.
All proposed drainage swale conveyances are in fact vegetated with TRM lining for
stabilization. We have included additional callout and revised swale detail for additional clarity.
Rip rap lining is only planned for use at culvert and discharge pipe outlet protections.
b. Per 15A NCAC 02H .1003(2)(b), projects shall be designed to maximize dispersed flow
through vegetated areas and minimize channelization of flow. Most all of the runoff from this
site appears to be collected and concentrated by passing it through the proposed non-
enforceable Wet Pond. While we are not reviewing the pond itself for compliance with MDC at
this time, the collection and concentration of runoff in this manner is not allowable inside of a
Low Density project per the cited statute. Please provide documentation stating that the
hdrinc.com
Use UPDATE/INSERTADDRESS feature in ribbon

proposed Wet Pond is necessary to meet local stormwater ordinances, revise the project
package to remove the Wet Pond and maximize dispersed flow, or revise the project package
to apply for a High Density permit, so that compliance with the Wet Pond MDC may be
evaluated.
The proposed project requires incorporation of a temporary sediment basin with a forebay,
porous baffles and skimmer to control the release of storm water. This was permitted under
NCDEQ Project ID:HARNE-2023-070. The design intent is to convert the sediment basin into
a Wet Pond for treatment of the post-construction stormwater run-off. While the proposed Built
Upon Area for the solid waste convenience center(78,190 SF or 1.63 AC) is less than 12% of
the Project Area (Site), it is over 20% of the drainage area for the sediment basin. In addition,
the County in the future may plan to construct additional recreational facilities at the site that
would increase the Built Upon Area closer to 12%, and maintaining the pond infrastructure
provides opportunity to convert back to sediment control and post-construction water treatment
following stabilization, with the pond infrastructure.
In addition, the wet pond provides retention of the storm water run-off so that the project can
meet the Harnett County Code Requirements (Article X:Natural Resources, Section 2.4.F) for
reduction of the 25-year, 24-hour storm run-off to no more that 10% over the pre-development
flow to Avents Creek(20.09 vs 19.92 cfs). See attached Code reference.
For these reasons we are proposing to maintain the Sediment Basin and Wet Pond conversion
for this project and have revised the Application to reflect a High Density project.
3. Consistency
Please revise the following for consistency:
a. Please revise the project documentation to reflect a consistent project name. The Application
states that the name of this project will be "Harnett County Northwest Convenience Center,"while
other project documentation states that the name of the project will be "Northwest Convenience
Center." Comments will be left where this issue is present.
We have revised the project documentation to reflect"Harnett County Northwest Convenience
Center"to match the naming convention on application and drawings.
4. Application
2x hard copies of the Application with the following corrections made, as required by 15A NCAC
02H .1042(2)(a) and Section VI, 1 of the Application:
a. Section I, 2—The information listed for this project's address does not appear to correspond to
the location given by the coordinates in Section I, 4. This project appears to be located on Oakridge
River Road. Please revise.

Location of Project(1.2) has been revised to indicate Oakridge River Road. The Latitude and
Longitude in Section 1,4 is correct.
b. Section IV, 10—The total amount of proposed BUA is listed as both 78,190 sf and 71,656 sf.
Please revise for consistency.
The BUA is 78,190 and has been corrected in the table.
c. Section IV, 10— If this project is to be permitted as a Low Density project, please revise the On-
Site Drainage Area line to match the Total Drainage Area line.
The project will be permitted as High Density as described above, so the on-site drainage area
reflects the drainage area to the Wet Pond SCM.
5. Supplement-EZ
lx hard copy of the complete, original Supplement-EZ Form with the following corrections made, as
required per Sections V &VI, 3 of the Application:
a. Cover Page
i. Line 1 — Please revise to read "Harnett County Northwest Convenience Center,"
for consistency.
Cover page has been updated.
ii. Line 6—Off-site SCMs are only applicable in cases where permitted projects are a portion of a
master permit, which contains the SCM in question. As this is not applicable to this project, please
revise to indicate "No."
Line 6 has been corrected.
iii. Line 7- Please indicate the width of the vegetated setback required from surface waters (30 ft
per 15A NCAC 02H .1017(10)). It is noted that there are no surface waters located on-site, however
we ask that this value be included on this line of the form (Lines 8-10 can remain as shown since
there are no surface waters on-site).
Line 7 has been updated to indicate 30 feet.
iv. Line 13—Since the proposed Wet Pond will not be reviewed as a part of this Low Density permit,
please remove the indicated Wet Pond from the Supplement-EZ form.

We are requesting High Density Permit review, so the Wet Pond SCM is maintained in the
Supplemental EZ-Form.
b. Drainage Areas Page
i. When there is only one Low Density drainage area in a project, the Low Density column of
this page will be identical to the Entire Site column. Please revise the Low Density column
to reflect this.
With High Density permit we have included both the Site and LD areas in the table.
ii. Line 4—Please revise this line to show N/A, as the proposed Wet Pond is not a portion
of this permit.
With the High Density permit we have included the Wet Pond SCM.
iii. Lines 20 and 21 —These may be left blank, since no Design Volume needs to be
calculated for a Low Density permit.
With the High Density permit we have included the Wet Pond design volumes.
iv. Line 22—This may be removed.
With the High Density permit we have included the additional information on Line 22.
c. Low Density Page
i. Since this project is being permitted as a Low Density project, please revise the
Supplement-EZ form to include this page and complete it. The swales that are inserted into
the Swale Table should correspond to what is shown in the provided plan sheets.
Not applicable with High Density application.
d. Wet Pond Page
i. Since the proposed Wet Pond is not reviewed as a part of the Low Density Permit, this
page is not required. Please omit this page from the next submission of the Supplement-EZ
form.
With the High Density permit have included the Wet Pond page.

6. Plans
2x hard copies of revised plan sheets with the following corrections made, as required by 15A
NCAC 02H .1042(2)(g)and Section VI, 8 of the Application:
a. Please identify and delineate the drainage areas to each swale on the main set of plans, as
required by Section VI, 8 of the Application.
Sheet OOH-02 includes the Drainage Area and Swale Location as depicted in the hydrologic
analysis. There are four(4) proposed vegetated drainage swales as summarized below.
Drainage Area Swale Comments
Area 5 SO Entrance Road Diversion
Area 3 S2 Steep Convenience Center Swale
Area 2 S1 Flat Convenience Center Swale
Area 1 DD Diversion Swale Around Wet Pond
b. Please delineate any wetlands present on the main set of plans or provide a note stating
that none exist. This wetlands delineation must be performed by a qualified professional.
This is required per Section VI, 8m of the Application.
Wetlands do not exist on the site. A note has been added to Sheet OOG-01.
c. Please identify and dimension all BUA on the main set of plans, as required by Section VI,
8j of the Application.
The BUA area is highlighted on the Sheet 0OC-01 Site Plan and a table has been added
from the Supplemental EZ form summarizing the site, drainage and BUA areas.
7. O&M Agreement
lx original, signed & notarized hard copy of the O&M Agreement Form, as required by 15A NCAC
02H .1042(2)(j)and Sections V&VI, 3 of the Application:
a. Please revise the project name to read "Harnett County Northwest Convenience Center."
Project name has been revised.
b. Please provide a revised O&M Agreement that corresponds to the permitting of a Low Density
area. Please do not include the Wet Pond information with this O&M Agreement, as it will not be a
part of the permit.
O&M Agreement for Wet Pond is included, and project name has been updated.

We are uploading a PDF of the response letter and updated documents and are submitting under
separate cover 2 hard copies of the Drawings, Stormwater EZ and the Supporting Narrative and
Calculations and 1 hard copy of the signed Application form and O&M Agreement.
Please do not hesitate to call if you should have any questions at(919)232-6682 or email at
[e-mail].
Sincerely,
HDR Engineering, Inc. of the Carolinas
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Je" S. Murray, PE, BCEE
Vice President
Enclosures