SW6231102_Response To Comments_20240315

HILUAW
ENGINEERING, PLLC
3417 Winterwind Circle,Sanford, NC 27330
PO Box 249,Sanford,NC 27331
Phone:[phone]
e-mail:[e-mail]
NC License#:P-0836
March 5,2024
Stormwater Program
NCDEQ Raleigh Regional Office
1628 Mail Service Center
Raleigh, North Carolina 27699
Reference: Stormwater Management Permit Application
Buffalo Creek Residential Subdivision
Hoke County, North Carolina
Dear Mr. Farkas:
Please find enclosed the following revised documents for the above referenced project:
1. As designed, the project does not appear to meet the definition of a low-density project.The
project appears to have excessive piping (prohibited per 15A NCACO2H .1003(2)(c)). Piping
that runs parallel to roadways can be replaced with
roadside ditches and pipes running perpendicular to roadways should be reduced in length, being
replaced with vegetated conveyances. Please either make the following changes to the project
design to meet the low-density requirements or revise the project design to meet the high-
density requirements.
a. Please remove the following pipes:
1. Pipe between CB111& C13110.
11. Pipe between CB110& C13109.
111. Pipe between CB108& D1107.
iv. Pipe between CB106& C13113.
V. Pipe between CB113 & C13114.
vi. Pipe between CB604& C13602.
vii. Pipe between CB503 & C13501.
viii. Pipe between CB206& C13205.
ix. Pipe between CB205 & C13203.

b. Please reduce the lengths of the following pipes:
1. Pipe between CB601& FES600.
11. Pipe between CB501& FES500.
111. Pipe between CB401& FES400.
iv. Pipe between CB301& FES300.
V. Pipe between CB201& FES200.
vi. Pipe between CB101& FES100.
Response:The parallel pipes have been removed and curb outlet swales have been designed to convey
storm water throughout the site.All pipe lengths have been shorted to the back of the building pads.
Due to the NCDOT requirements for depth of pipes in the roadways and the subdivision being designed
as a septic lot development the pipe lengths were set to provide a minimum 100 ft of curb outlet swale
prior to entering into the main curb outlet swale or into another pipe cross-section. The start of the
ditch locations was picked also to provide undisturbed areas of soil on the sides of the lot pads for
septic area in addition to the areas on the back of the lots.
1. Please correct the following issues with the swale designs:
a. Please ensure that the design information shown in the plans, design
calculations and Supplement-EZ Form are consistent.
Response:The design calculations, plans and EZ form has been updated to provide consistent
information between them.The 10-yr and 25-yr storm calculations have been provided for each curb
outlet swale.
b. Please provide a swale cross-sectional detail in the main set of plans.This item is required
per Section VI, 81. at a minimum, the bottom width, side slope, depth, and vegetation
should be specified.
Response: Sheet C10 has been updated with a curb outlet swale detail. The specifics of each swale
section has been added to a table on this sheet also.
c. PD-2:
vii. This Swale is a curb outlet Swale. Please ensure that this Swale meets the
curb outlet Swale requirements outlined in 15A NCAC 02H .1003(2)(d).
viii. Per the plans, the longitudinal slope varies along the length of the Swale. Please
either divide the Swale into sections (with similar geometries)or use the steepest
longitudinal slope for the Swale calculations.
ix. The provided velocities and depths shown in the calculations and shown in the
Supplement-EZ Form do not appear to match.
x. The design information shown in the calculations and shown in the plans do not
correspond. Please revise as needed.
Response: The swale has been divided into separate sections per slope and designed to meet curb
outlet requirements.All calculations have been updated to match between plans, calculations and
forms.

a. PD-1A& 113:
A Please include the design of these swales in the Supplement-EZ Form.
Response: The swale has been added to the form and all calculations updated.
b. PD-100:
x11.Please include the design of this swale in the Supplement-EZ Form.
x111.This swale is a curb outlet swale. Please ensure that this swale meets the curb
outlet swale requirements outlined in 15A NCAC 02H .1003(2)(d).
xiv. The design information shown in the calculations and shown in the plans do not
correspond. Please revise as needed.
Response: The swale has been added to the form and all calculations updated.
c. Swales downstream of FES 200& FES 300—These are considered curb outlet swales,
please provide calculations showing that these areas meet the curb outlet swale
requirements outlined in 15A NCAC 02H .1003(2)(d).
Response: The swale has been added to the form and all calculations updated.
a. Swales downstream of FES 200& FES 300—These are considered curb outlet swales,
please provide calculations showing that these areas meet the curb outlet swale
requirements outlined in 15A NCAC 02H .1003(2)(d).
Response: The swale has been added to the form and all calculations updated.
2. Please show the required vegetated setback from surface waters in the main set of plans. This
item is required per 15A NCAC 02H .1042(2)(g)(iii).
Response: The vegetative setback from wetlands has been added to plan sheet C2-C3.
3. Please correct the following issues with the provided calculations:
a. Please provide the source for the rainfall intensity information used in the swale
calculations.
Response: The NOAA intensity sheet has been added the Appendices in the calculations report.
b. Please include the Manning's"n"value used in the swale calculations.
Response: The mannings "n" has been added to the calculations.
c. Please ensure that the units for values used in the swale calculations are provided. For
example, channel slope, depth, bottom width, side slopes, &velocities values do not have
units associated with them (some of these units can be assumed, however they really
should be included for clarity).
Response: The units have been added to the calculations.
d. There appears to be a mismatch between the rational coefficient "C"values shown in the
calculations and those shown in the Supplement-EZ Form. Please revise as needed.
Response: The C value for the swale has been updated to match the form and the calculations.

4. Please correct the following issues with the Application Form:
a. Section III, 1.b—Please provide street address for the applicant, Graceland
Development, LLC.This item is required per 15A NCAC 02H .1042(2)(a)(viii).
Response: The street address has been added to the application.
b. Section IV, 10—Please ensure that all off the BUA allocated to the individual lots is accounted
for in the "On-site Buildings/Lots" line and not in both the "On-site Buildings/Lots" &"Other
on-site" lines.
Response: The other value was illustrating additional BUA (driveway, sidewalk, accessory buildings,
etc.). It has been removed from that section and added to the on-site building/lots.
c. Section IX—Since the Applicant is also the Property Owner, Section IX of the
Application should not be filled out.
Response: The section has been left blank.
5. Please correct the following issues with the O&M Agreement Form, the provided O&M
Agreement is for "Carter Farms Subdivision—Phase 1".
Response: The project name has been corrected.
6. Please correct the following issues with the Supplement-EZ Form:
a. Drainage Areas Page:
1. Line 4—Low-density projects typically only have 1 drainage area that is equal to
the project area. Please revise.
H. LID Column 1—For this project,the low-density drainage area is equal to the project
area. This column will be the same as the "Entire Site" column.
Response: The drainage area and column 1 have been corrected to show only one DA and the
columns match.
b. Low-Density Page:
1. Line 4 — If the side slopes of the swales varies between the swales, place the
steepest side slope for the swales in this cell and elaborate on which swales
have which side slopes in the additional information section.
Response: All swales have been updated to be 3:1 at the steepest.
H. Line 6 — If only some of the swales are designed to meet the curb outlet
swale design requirements, please elaborate on which swales are curb
outlet swales in the additional information section.
Response: All swales have been updated to meet curb outlet swale requirements and form
updated.

111. Line 7—Per 15A NCAC 02H .1003(2)(d),the maximum allowable
longitudinal slope of a curb outlet swale is 5%.
Response: All swales have been updated to meet curb outlet swale requirements
and form updated.
iv. Lines 7-11-These values should be based on the actual design
characteristics of the curb outlet swales for this project.
Response: All swales have been updated to meet curb outlet swale requirements and form
updated.
V. Line 8—This value does not correspond to the provided swale design in the
calculations.
Response: All swales have been updated to meet curb outlet swale requirements
and form updated.
vi. Line 12—This item is required per 15A NCAC 02H .1003(4)(e).
Response: Line 12 has been updated to yes.
vii. It is unclear which swales Swales 2 &3 in the swale table are.
Response: All swales have been number matched with form to swale numbers in plans.
viii. If the swale numbers used in the plans and Supplement-EZ Form do not
match, please specify which swale numbers correspond to which swales in
the additional information section (Ex. PD-2 =Swale 1).
Response: All swales have been number matched with form to swale numbers in plans.
ix. Per the design table provided in Part C-11 of the Manual, Bermuda grass in
sandy soils is limited to a maximum velocity of 5.0 fps (6.0 fps is shown for
swale#1).
Response: A permanent liner from NAG has been specified with vegetation that will allow for
higher velocities and shear stresses.
If after review of the submittal package you have any questions, comments or if you require any
additional information please do not hesitate to contact me at (919) 499-8759 or
[e-mail]. Thank you for your assistance.
Sincerely,
Hilliard Engineering, PLLC.
Michael Blakley