SW3180905_Add Info Request_20210514

ROY COOPER
Governor
MICHAEL S. REGAN
Secretary
BRIAN WRENN
Director
Dale Stewart, PE
LandDesign
223 North Graham Street
Charlotte, NC 28202
NORTH CAROLINA
Environmental Quality
May 14, 2021
Subject: Request for Additional Information
Stormwater Permit No. SW3180905
Twin Lakes
Union County
Dear Mr. Stewart:
The Division of Energy, Mineral and Land Resources (DEMLR), received a Stormwater
Management Permit Major Modification Application for the subject project on March 17. A
review of that information has determined that the application is not complete. The following
information is needed to continue the stormwater review:
1. Please address the following comments with regard to the low density area:
a. Why was the low density area broken up into two areas on the design plans? This
should be handled as one area as it was on the application form.
b. The low density area is designed with 27% BUA according to the application
form (26% for LD1 and 28% for LD2 according to Supplement EZ). This amount
of built -upon area exceeds the 24% threshold for low density. The built -upon area
in the low density area must be reduced or the area will be required to be designed
as high density [15A NCAC 02H .1003(2)(a) and .1017(4)].
c. The streets in the low density area use curb and gutter and pipe runoff away from
the site. This is not allowed under the low density regulations, which specify that
"Stormwater that cannot be released as dispersed flow shall be transported by
vegetated conveyances. A minimal amount of non -vegetated conveyances for
erosion protection or piping for driveways or culverts under a road shall be
allowed by the permitting authority when it cannot be avoided. " The design does
not meet the low density standards and shall be revised to remove the piping and
propose vegetated conveyances or the area will be required to be designed as high
density [15A NCAC 02H .1003(2)(c)].
d. A portion of the low density area at the southeastern part of the site falls in an
area labeled "Future Senior Living Area". Note that the application does not
specify any future built -upon area in the low density area. Any future
development in this area will require a major modification to the permit. This area
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cannot be used in the density calculations for any future development [15A
NCAC 02H .1002(38)].
e. Part of the development on the western side of the project was not included in the
low density area (parts of lots 45-48). This area should be included regardless of
where the runoff drains because it is an area regulated under this permit.
2. Each wet pond detail (Sheets C416, C417, and C418) have a note on the wet pond in a
text box with design information for the wet pond. The label for "TOP OF BERM" on
each of these details in incorrect.
3. The drain times for the wet ponds should be calculated using the orifice equation and
methodology in Part B: Stormwater Calculations of the Stormwater Design Manual.
When calculating the drawdown time using this standard calculation both Wet Pond 2
and Wet Pond 3 drain in less that two days. Wet ponds are required to drain the runoff
from the design storm in 2-5 days [15A NCAC 02H .1053(7)].
4. Please show an easement and maintenance access for each SCM that complies with
General MDC 8 and 9 [15A NCAC 02H .1050(8) & (9)].
5. Please use the most up-to-date version of O&M EZ, which includes the option to specify
areas of low density.
6. Please upload an electronic copy of the property deed. This is required on all submittals
and is currently missing from the permit file.
7. 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:
hgps:Hedocs.deq.nc.gov/Forms/SW_Project Submittal
Please note that this request for additional information is in response to a preliminary review.
The requested information should be received by this Office prior to June 13, 2021, or the
application will be returned as incomplete. The return of a project will necessitate resubmittal
of all required items, including the application fee. Please reference the State assigned project
number SW3180905 on all correspondence.
If you need additional time to submit the information, please submit your request for a time
extension to the Division at the contact below. The request must indicate the date by which you
expect to submit the required information. The Division is allowed 90 days from the receipt of
a completed application to issue the permit.
The construction of any impervious surfaces, other than a construction entrance under an
approved Sedimentation Erosion Control Plan, is a violation of NCGS 143-215.1 and is subject
to enforcement action pursuant to NCGS 143-215.6A.
If you have any questions concerning this matter please feel free to contact me at
Corey.Anen(cncdenr.gov or [phone]. Please note that due to the ongoing Covid-19
pandemic, I will be teleworking and will be most easily reached by email.

Sincerely,
Steven Corey Anen, PE
Environmental Engineer
Stormwater Program
cc: Mooresville Regional Office