SW6230803_Response To Comments_20231211

4MCKIM&CREED ENGINEERS
SURVEYORS
PLANNERS
December 11, 2023 M&C (04739-0014)
Mr.Jim Farkas
State Stormwater Engineer
DEMLR Post-Construction Stormwater Program
512 N. Salisbury Street, Office 640M
Raleigh, NC 27604
RE: Request for Additional Information
Stormwater Permit No.SW6230803
Dove Subdivision—North (Now Bloom Subdivision—North)
Harnett County
Below are our responses to the request stormwater review and request for information
comments received on November 9th, 2023. The revised plans are included with this
submittal for review. Please let us know if you have any questions.
Comment Response Format
Comment
Response:
1. Please provide calculations showing the following:
a. The stormwater outlets are stable in accordance with 15A NCAC 02H
.1003(5). If the project does not require riprap outlet protection
downstream of the stormwater outlets, please provide calculations
showing that the outlets are stable as designed.
Response: Riprap aprons have been added to discharge points.
Calculations and details have been added to the plans.
b. Design calculations for the proposed roadside ditches. Roadside ditches
are vegetated conveyances and must be demonstrated to me
requirements of 15A NCAC 02H .1003(c).
Response: Additional ditches with calculations and details have been
1 730 Varsity Drive added. Please see sheet C12.2 for details,velocity calculations, and
required stabilization.
Suite 500
c. Please clarify the swale calculation. It is unclear what Manning's
Raleigh, NC 27606 roughness coefficient was used to determine the velocities for the
swales. In addition,the swale flow velocity during the design storm is not
included in the calculations (it is noted that these velocities are included
919.233.8091 in the Supplement-EZ Form, but these velocities, as well as information
on the swale geometry should be included in the calculations so that they
Fax [phone] can be verified).
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Response: Additional ditches have been added to the plans and calculations. The calculations
now include the Manning's roughness coefficients and calculated velocities.
2. Please correct the following issue with the plan set:
a. Please delineate the drainage area to the proposed swales/vegetated conveyances in the
main set of plans. This item is required per 15A NCAC 02H .1042(2)(g)(iv) and Section VI, 80
of the Application. Please revise as needed.
Response: Drainage area delineation lines for all permanent ditches have been added and
called out on sheets C7.1—C7.2.
3. Please correct the following issues with the application:
a. Section III, 1.b—Please provide the contact information (email address and phone number)
for the applicant.This information is required per 15A NCAC 02H .1042(2)(a)(vii).
Response: Additional contact information has been added.
b. Section III, 2.b—Please provide the property owners (email address and phone number)for
the applicant.This information is required per 15A NCAC 02H .1042(2)(a)(ix).
Response: Additional contact information has been added.
c. Section IV, 10— Please exclude the surface water area from the total and on-site drainage
areas. For this project,these values will correspond to the value shown in Section IV, 7 of the
Application. Please recalculate the percent impervious area. For this project, this value will
correspond to the value in Section IV, 8 of the Application.
Response: The surface water area has been subtracted from the total drainage area. The
percent impervious has been recalculated.
4. Please correct the following issues with the Supplement-EZ Form:
a. Cover Page:
i. Line 2—Please exclude the surface water area from this item.This item should correspond
to Section IV, 7 of the Application.
Response: The surface water area has been subtracted from the total property area.
b. Drainage Areas Page:
i. Lines 5 & 6 — Please exclude the surface water area from these items. For this project,
these items should correspond to Section IV, 7 of the Application.
Response: The surface water area has been subtracted from the total drainage area.
c. Low-Density Page:
i. Please include the design information for the roadside ditches.
Response: Design information for the roadside ditches has been added.
5. If you have not already done so, please reach out to Harnett County as this project is located
within Harnett County's water supply watershed jurisdiction and requires their approval (in
addition to being within the State's post-construction jurisdiction and requiring the State's
approval).
Response: Understood.
v McKIM&CREED

Please provide approval and/or additional comments. If you have any questions, please do not
hesitate to contact me, at 919-233-8091 or at [e-mail].
Sincerely,
McKIM &CREED, INC
dif\C-N41-
Adam E. Freeman, PE
Senior Project Engineer
McKIM&CREED