SW4240401_Response To Comments_20240801

CPT
Engineering & Surveying, Inc.
July 31, 2024
Brianna Holland
Stormwater Engineer
DEMLR Post-Construction Stormwater Program
512 North Salisbury Street, Office 640M
Raleigh, NC 27604
Re: Stormwater Permit No. SW4240401
WhiteHall Village South
Forsyth County
Dear Brianna:
Please find attached two hard copies of the revised plan sheets, one hard copy of other documents and
this Response Letter. We did our best to address the comments from your e-mail letter dated July 3,
2024 in a complete and thorough manner. Below are the comments and the written response, which are
in red.
1. BIORETENTION MDC 1. SEPARATION FROM THE SHWT.
a. Revise the Supplement-EZ/plans for consistency with the SHWT report to ensure the
lowest point of the bio-retention cell shall be a minimum of two feet above the SHWT.
Revised Supplement-EZ Form with New SHWT Information is attached.
2. BIORETENTION MDC 3: PEAK ATTENUATION VOLUME.
a. Bioretention cells may store peak attenuation volume at a depth of up to 24 inches
above the planting surface. The peak attenuation outlet shall be a maximum of 18
inches above the planting surface. Please revise package accordingly. Revised Bio-cell
outlet box to meet MDC requirements and revised calculations are attached.
3. BIORETENTION MDC 6: MEDIA MIX.
There is a typo in the manual. Please revise to meet 15A NCAC 02H .1052 (6).
The media shall be a homogeneous engineered media blend with approximate
volumes of:
(a) 75 to 85 percent medium to coarse washed sand (ASTM C33, AASHTOM 6/M80, ASTM
C330, AASHTO M195, or the equivalent);
(b) 8 to 10 percent fines (silt and clay); and
(c) 5 to 10 percent organic matter (such as pine bark fines).
Ensure this mix is specified on the plans. The plans have been revised to match
15A NCAC 02H .1052 (6).
4400 Tyning Street•High Point,NC 27265 Phone: [phone], ext 305 •Fax: [phone]
[e-mail]

4. GENERAL MDC 4: EROSION PROTECTION.
The inlets SCMs shall be designed to protect the SCM from erosion resulting from
stormwater discharges. The outlets of SCMs shall be designed so that they do not cause
erosion immediately downslope of the discharge point during the peak flow from the
10 year storm event as shown by engineering calculations. Ensure sizing and class
information corresponding to the plans is shown on the calculations. Both Bio-cells have
a rip-rap baffle at the inlets. Bio-cell #1 ties to an existing storm sewer and Bio-cell #2 has
an outlet pipe. See attached Rip-Rap nomograph.
5. 15A NCAC 02H .1042 (2)(g)(vi),
Maintenance access routes and easements must be shown on the main set of plans.
This easement must have a minimum width of ten feet, not include any slopes steeper
than 3:1, extend to the nearest public right-of-way, and include the entire SCM footprint
(General MDCs 8 & 9) (see guidance under MDC 9 in Part C-0 of the Manual).
Included with each Bio-cell Plan is the Grading & Drainage Plan (sheet C-4) so the SCM
Access Easements for both bio-cells can be seen connecting to the public right-of-way.
6. Supplement-EZ
1x hard copy of the complete, original Supplement-EZ Form is required per Sections V &
VI, 3 of the Application
a. Cover— Line 7-8: While there is no surface water, and therefore no vegetated
setbacks associated with this project, please fill in. Per 15A NCAC 02H .1017 (10), the
vegetated setback shall be at least 30 feet in width. See attached revised Supplement
— EZ Form. Line 7 was changed to 30' and line 8 was changed to yes.
7. Ensure all required documents are uploaded to the electronic repository. It was
noted the O&M Agreement was not included in the last submission. All required/revised
plans and documents will/have been upload to the electronic repository
8. Please provide a Response to Comments letter indicating, in a point-by-point manner,
how each of the above comments has been addressed. This item is required per 15A NCAC
02H .1042(3)(b). See attached Comment Response Letter
9. Provide PDFS of all revisions, 2 hardcopies of revised plan sheets, 1 hard copy of other
documents, and a response to comments letter briefly describing how the comments have
been addressed. See attached items.
Hopefully all the comments have been satisfactorily addressed to complete the review process for
WhiteHall Village South. Please let us know if you have any additional questions or need more
information.
Sincerely,
Mike Vena le
Civil / Survey Technician
CPT Engineering and Surveying, Inc.