SW6221001_Response To Comments_20221214

G
GRADIENT
LAND • WATER• INNOVATION
December 14, 2022
Mr. Jim Farkas
Division of Energy Mineral and Land Resources
North Carolina Department of Environmental Quality
1612 Mail Service Center
512 North Salisbury Street, Office 640E
Raleigh, NC 27699-1612
Re: Macridge &t Chicken Road Intersection Improvements
Dear Mr. Farkas:
Enclosed is information pertaining to our application for the state Stormwater Management Permit
Application for the above referenced project. In addition to this letter addressing comments,
included as a part of this submittal are the following:
• Two folded full-size sets (22x34) of the revised sheet to the project plans, 95% Design for
Regulatory Review, dated 12/14/2022.
• One copy of Soil Report/Letter from Hal Owen &t Associates, dated 7 January 2022 (pertaining
to soil boring at SCM #2).
• One copy of Soil Report/Letter from Hal Owen &t Associates, dated 3 December 2021
(pertaining to soil borings at SCM #1).
• One copy of the corrected Supplement-EZ form, sealed, signed and dated December 14, 2022.
Additionally, outlined below, we are responding to your review comments sent to us via email on
December 12, 2022:
Please correct the following:
Please provide the existing ground surface elevations for the soil borings so that the SHWT
elevations can be determined (this item is required per Bioretention MDC 1). It is noted that
the depth from the existing ground surface elevation to the SHWT is provided, however, we
need to be able to verify the elevation of the SHWT.
Response: The existing ground elevations have been added to the soil report/letters. The
information is included (shown in yellow and red).
230 Donaldson Street, Suite 600A Fayetteville, NC 28301 1 910.824.7731
1513 Walnut Street, Suite 230 Cary, NC 27511 1 910.824.7731
www.gradientNC.com

Please correct the following issues with the Supplement-EZ Form:
o Drainage Areas Page:
■ Line 18 - Please include the %BUA for the entire site and two drainage areas
(This information should correspond to Section IV, 8 Et 10 of the Application
respectively).
Response: Line 18 has been included and corrected.
o Bioretention Cell Page:
■ Line 24 — Please clarify the peak attenuation elevation/depth. The provided peak
attenuation depth for SCM2 (5") is less than the ponding depth of the design storm
(7"). If the peak attenuation elevation/depth is based on a large storm event (such as
the 10-year or 100-year storm event) these values should be updated to reflect this. If
the SCMs are not designed to attenuate peak flows, these items (and Lines 23 & 25)
should be revised to reflect this.
Response: The above information has been corrected and clarified.
■ Line 26 — For an SCM with multiple soil borings, either the more conservative
infiltration rate or the average infiltration rate should be used. Please revise as needed
(providing the existing ground surface elevations for the soil borings will allow us to
verify the infiltration rate valued used).
Response: The more conservative infiltration rate has been included. Please
see the attached soil report/letters that show the elevations relative to the soil
depths.
All documents listed herein have also been uploaded to the State Stormwater portal at
https://edocs.deg.nc.gov/Forms/SW-Supplemental-Upload as requested (the electronic documents
prefixed with a date of "20221214-").
Should you require any additional information, please do not hesitate to contact us.
Sincerely,
GRADIENT, PLLC
C. Heath Wadsworth, PE