SW3210201_Add Info Request_20210414

ROY COOPER
Governor
DIONNE DELLFGATTI
Secretary
BRIAN WRENN
Director
NORTH CAROLINA
Environmental Quality
April 14, 2021
Kevin Thorstad, PE
Little Diversified Architecture Consulting
4245 North Fairfax Drive, Suite 650
Arlington, VA 22203
Subject: Request for Additional Information
Stormwater Permit No. SW3210201
Union County Southwest Regional Library
Union County
Dear Mr. Thorstad:
The Division of Energy, Mineral and Land Resources (DEMLR), received a Stormwater
Management Permit Application for the subject project on February 22, 2021. A review of that
information has determined that the application is not complete. The following information is
needed to continue the stormwater review:
The Applicant's Certification was not signed. This is required on all applications. The
Property Owner Authorization is only required when the applicant is not the property
owner.
2. The site as designed does meet the low density design criteria. The intent of a low density
design is to prevent channelization of flow and provide sheet flow off of built upon areas
onto permeable surfaces. A minimal amount of piping is allowed only for culverts under
roadways or driveways or for erosion control. The proposed design uses far more piping
than allowed. Please revise the design to meet the low density criteria or it will be
considered a high density design and a primary SCM will be required to provide runoff
treatment. Note that level spreader -filter strips are not a primary SCM. The relevant
section of the Stormwater Management Rules is shown below.
15A NCAC 02H .1003(3): DESIGN REQUIREMENTS FOR LOW DENSITY PROJECTS. Low
density projects shall meet the following minimum design criteria:
(a) DENSITY THRESHOLDS. Low density projects shall not exceed the low density
development thresholds set forth in the stormwater programs to which they are subject pursuant
to Rules .1017, .1019, and .1021 of this Section. For projects subject to the requirements for Non -
Coastal High Quality Waters and Outstanding Resource Waters, dwelling unit per acre may be
used instead of density to establish low density status for single-family detached residential
development as set forth in Rule .1021 in this Section;
(b) DISPERSED FLOW. Projects shall be designed to maximize dispersed flow through
vegetated areas and minimize channelization of flow;
North Carolina Department of Environmental Quality I Division of Energy, Mineral and Land Resources
512 North Salisbury Street 1 1612 Mail Service Center I Raleigh, North Carolina 27699-1612
NORTH CAROLINA
uepaa nt of enmmnmmi Q.1; 919.707.9200

(c) VEGETATED CONVEYANCES. 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. Vegetated conveyances shall
meet the following requirements:
(i) Side slopes shall be no steeper than 3:1 (horizontal to vertical) unless it is
demonstrated to the permitting authority that the soils and vegetation will remain stable
in perpetuity based on engineering calculations and on -site soil investigation; and
(ii) The conveyance shall be designed so that it does not erode during the peak
flow from the 10-year storm as demonstrated by engineering calculations.
3. 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:Hedocs.deg.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 May 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 SW3210201 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.AnenAmcdenr.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
D E Q�� North Carolina Department of Environmental Quality I Division of Energy, Mineral and Land Resources
512 North Salisbury Street 1 1612 Mail Service Center I Raleigh, North Carolina 27699-1612
NORTH CAROLINA -
D.panm.mof Envlloamaotal Duality 919.707.9200