SW4201101_Stormwater_Permit_SW4201101_Response_Letter_20210105

January 5, 2021
Division of Energy, Mineral & Land Resources
C/O Corey Anen
Stormwater Program
1612 Mail Service Center
512 North Salisbury Street
Raleigh, NC 27699-1612
RE: Request for Additional Information
Stormwater Permit No. SW4201101
Heritage Oaks Section II – Residential Subdivision
Forsyth County

Mr. Anen:

Please find the requested additional information in the following reply and enclosed plans and
documents. I have addressed each area of our request below:

1. Please delineate any wetlands onsite or add a note that none exist \[15A NCAC02H
.1042(2)(g)(ii)\].

I have included a report prepared by a local firm that outlines their findings for stream(s) and
wetland(s). The plan sheets affected by this further information have been updated and
included in this submission.

2. Sheet C2-5 shows a slope on the roadside ditches as 2:1. The maximum allowable side slope
for vegetated conveyances on low density projects is 3:1 \[15A NCAC02H .1003(2)(c)(i)\].

The revised sheet is included in this submission.

3. The low density only allow for a minimal amount of non-vegetated conveyances for erosion
protection or piping for driveways. Sheet C4-0 show areas where runoff is being piped away
from the roadways through 20’ drainage easements before being discharged. The
conveyances in these drainage easements should use vegetated conveyances rather than
piping to meet the low density requirements \[15A NCAC 02H .1003(c)\].

We discussed this item in some detail during our December 16, 2020 phone conversation.
The site design is to carry water out of the steep or long continuous ditch lines at regular
intervals to reduce soil erosion due to velocity or depth of water in the ditches. The concept
is based on collecting a reasonable amount of water in the vegetated conveyances and then
transporting it out of the ditch lines at regular intervals. This is best accomplished with catch
basins and pipe. My professional experience is that sharp turns in ditch lines lead to long
term erosion problems and it is best to use catchments to turn the water instead.
PO Box 669 Walkertown, NC 27051 336-748-0071

At the entry point of the site (Heritage Oaks Lane STA 0+00thru 3+50) and along Heritage
Birch Court, the road grade/ditchlines are steep, and velocities become erosive. The water is
collected from the ditch lines and transported via catch basin and pipe using 1% grades to
daylight as quickly as possible.

From the intersection of Heritage Maple Lane and Heritage Oaks Lane, the road grade/ditch
lines are much flatter at 1-1.25%. These long runs accumulate depth of water. The water is
removed from the ditchline at approximately 200’ intervals using catch basins and pipe at
1% grades to daylight as quickly as possible. All the pipe runs are designed to minimize the
use of pipe, daylight as quickly as possible and return storm water to vegetated conveyances
to the maximum extent possible.

4. Provide pdfs of all revisions, 2 hardcopies of revised plan sheets, and 1 hardcopy of other
documents. Pdfs must be uploaded using the form at:
https://edocs.deq.nc.gov/Forms/SW_Project_Submittal
Enclosed in this response submittal and submitted via the portal is:
a. This response letter
b.The environmental report
c. Revised plan sheets C-1.1 UT, C-2.5, C-4.0

Best Regards,

Alex Carter, PE
PO Box 669 Walkertown, NC 27051 336-748-0071