SW3200903_Add Info Request2_20210412

ROY COOPER
- a
Governor
y a2
DIONNE DELLFGATTI
�.�xi
*�`�^'^0"'*
Secretary
BRIAN WRENN
NORTH CAROLINA
Director
Environmental Quality
April 12, 2021
Chase Burton, PE
Burton Engineering Associates
5950 Fairview Road, Suite 100
Charlotte, NC 28210
Subject: Request for Additional Information
Stormwater Permit No. SW3200903
Project ETARC
Catawba County
Dear Mr. Burton:
The Division of Energy, Mineral and Land Resources (DEMLR), received a Stormwater
Management Permit Application for the subject project on September 29, 2020 and additional
information on March 10, 2021. A review of that information has determined that the
application is not complete. The following information is needed to continue the stormwater
review:
REPEAT COMMENT: On Page 2 of the SWU-101 Application Form (Part III. Lc) the
applicant is listed as the property owner. However, Part III.2.a and the submitted deed show
Oakwood Farm, LLC as the property owner. Please correct this discrepancy. Also, if the
applicant is the lessee or purchaser please also submit a copy of the lease or purchase
agreement.
This comment was not addressed in the resubmittal.
2. REPEAT COMMENT (Original comments 4 and 5 combined): The temporary pool elevation
must be calculated using the total volume from the 1" storm, not by routing a 1", 24-hour
storm through the wet pond. The temporary pool elevation should be calculated as the stage
at which the total runoff volume from the 1" storm is reached. The outlet discharge was
calculated assuming a 12" orifice instead of two 6" orifices. Because the orifice area
calculation is not linear this significantly affects the calculated flow rate leaving the wet
pond. Please calculate the drawdown using two 6" orifices instead of one 12" orifice.
The design permanent pool elevation is 830.5 and the calculated water quality volume is 3.244
ac ft at El. 831.14. With a permanent pool volume of 9.555 ac ft, the water quality elevation
should occur when the total storage in the pond is 9.555 + 3.244 = 12.799 ac ft. This occurs at
an elevation between El. 831 (10.795 ac ft) and El. 832 (13.375 ac ft), but does not correspond
to El. 831.14. The correct elevation for the water quality volume must be interpolated here. This
elevation must be used for calculating the drawdown time.
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 ntntenmmnmmiQ.J; 919.707.9200

The orifice diameter used in the calculations is 12 ", but the design shows two 6" orifices. The
two 6" orifices cannot be replaced with a single 12 " orifice because the cross sectional area of a
single 12 " orifice is far larger than that of two 6" orifices. The flow should be calculated using
either two orifices or a single orifice with a diameter that provides an equal cross sectional area
to two 6" orifices.
In addition, there appears to be a mistake in the calculation spreadsheet submitted for the wet
pond. The driving head was entered as 0.21 ft (H/3 in accordance with the Design Manual). My
calculations show that the Avg Q calculated in your spreadsheet is lower than the actual average
flow. It appears that this is because the spreadsheet is already dividing the inputted value by 3 to
account for the requirements in the manual. The head entered here should probably be the actual
head at the water quality elevation.
3. Provide pdfs of all revisions, 2 hardcopies of revised plan sheets, and l hardcopy of other
documents. Pdfs must be uploaded using the form at:
hgps: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 12, 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 SW3200903 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(d),ncdenr.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, V4�1�
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