SW3210801_Add Info_20211108

ROY COOPER
Governor
ELIZABETH S. BISER
Secretary
BRIAN WRENN
Director
Brad Smith, PE
1020 Euclid Avenue
Charlotte, NC 28203
NORTH CAROLINA
Environmental Quality
November 8, 2021
Subject: Second Request for Additional Information
Stormwater Permit No. SW3210801
1-85 Commerce Center
Rowan County
Dear Mr. Smith:
The Division of Energy, Mineral and Land Resources (DEMLR), received a Stormwater
Management Permit Application for the subject project on October 7, 2021. A review of that
information has determined that the application is not complete. The following information is
needed to continue the stormwater review:
Original Comment 4 — "The percent impervious cover of the project area appears to be
incorrectly calculated (Section IV, 8). The percent impervious cover is calculated as
follows: [% Impervious Cover] = [Total Proposed BUA] / [Project Area]" Per the
information in the submission, the total amount of proposed BUA within the project area
is 29.43 ac (20.16 ac is shown in the calculation of this item) and Section IV, 7 shows the
project area as 41.87 ac (40.35 ac is used in the calculation of this item). Also,
performing the calculation as shown for this item [(20.16 / 40.35) * 100%] results in
a %BUA of 50%, not the 69.8% as shown. Please revise as needed for correctness and
consistency.
2. Original Comment 12 —"The design of the wet pond could not be fully reviewed for
compliance with the MDCs since stage -storage tables for the wet pond were not
provided... The stage -storage tables are required to ensure compliance with Wet Pond
MDCs 1, 2, 3, 5, 6, & 7. " The following calculation errors were noted from reviewing the
provided stage -storage tables:
a. The volume of the main pools and the forebays should not include the sediment
storage zone since this portion of the pond is intended to be filled up with
sediment and can therefore not count towards provided storage volume.
D E Q North Carolina Department of Environmental Quality I Division of Energy, Mineral and Land Resources
512 North Salisbury Street 11612 Mail Service Center I Raleigh, North Carolina 27699-1612
NORTH CAROLINA _
De"dm,tomD,im mUlDwnry 919.707.9200

b. The calculated forebay volumes appear to be incorrect and may be too small. The
forebay volume is the volume of water that can be stored in the forebay between
the top of the sediment storage zone and the permanent pool. NOTE: I did not
notice a detail for the berm separating the forebay from the main pool in the plans.
Without this detail, it is assumed that the berm is made up of pervious stone
which would allow water stored in the forebay to seep into the main pool and
equalize at the permanent pool elevation. If the berm is made up of something
impervious that would prevent this from happening, then you would be able to
count the forebay volume up to the point at which it spills over into the main pool
as "forebay volume".
c. The cross -sectional area of section 4 wet pond 4 at elevation 770 appears to be
incorrect. The cross -sectional area of this portion of the wet pond (21,185.3 sf) is
smaller than the cross -sectional area of this portion of the wet pond at elevation
769 (26,033.2 sf). Cross -sectional areas of a wet pond should increase as the
elevation increases.
d. The temporary pool surface elevation (765.26) is located above the invert of the
bypass weir located in the outlet structure (at elevation 765.2). Strictly speaking,
this is allowable and not against the MDCs for a wet pond, however it is a bad
design practice since the design volume of the wet pond should be stored below
any bypass devices and allowed to be drawn down via the drawdown orifice. If
you will be leaving the bypass weir below the temporary pool surface elevation,
please make sure to account for its impact on the drawdown time for the design
volume.
3. Original Comment 20 — "Please correct the following issues with the O&MAgreement
Form... " An updated version of the O&M Agreement Form was not provided in this
resubmission. Please provide this item with the corrections requested from the prior
letter.
4. Original Comment 21.b.iy.2 — "Please correct the following issues with the
Supplement-EZ Form... Drainage Area Page... Lines 5-7 — The `drainage area' of the
entire site is the entire project area and should correspond to the value shown in Section
IV, 7... " The "drainage area" information entered into the entire site column does not
correspond to the total project area information from Section IV, 10 of the Application.
The entire site column is not merely a sum of the information in the drainage area
columns, but rather an accounting of the entire project area.
5. Original Comment 22 — "Provide pdfs of all revisions..." Please upload the electronic
files from the 10/7/2021 submission to the link provided below. Electronic files are
required per 15A NCAC 02H .1042(2).
6. There appears to be 17,921 sf of "Other" BUA listed in the Application that does not
appear in the Supplement-EZ Form. Please revise as needed for correctness and
consistency.

7. The amount of BUA within the drainage area to the proposed wet pond is shown as 28.16
ac in the calculations and as 29.43 ac in the Application and Supplement-EZ Form (This
may impact the design volume of the SCM). Please revise as needed for correctness and
consistency.
8. Any off -site areas that drain to the proposed wet pond must be accounted for at their full
build -out potential (per 15A NCAC 02h .1003(3)(b)). It is recommended to bypass these
off -site areas around the proposed SCM since the Applicant has no control over future
development of these off -site areas and can become non -complaint with this permit at no
fault of their own. If it is not possible to divert this off -site drainage area around the
proposed SCM, it is recommended to have the off -site property owner and the Applicant
enter into a legal agreement limiting the amount of BUA and drainage area that the off -
site property owner can direct to the proposed SCM. If this option is not feasible, the off -
site area can be accounted for at the full build -out potential of 100% BUA. The off -site
area being developed to the point where it becomes 100% BUA may not seem like a
likely outcome, but it is possible and therefore the full build -out potential of this area.
9. Please correct the following issues with the Wet Pond Page of the Supplement-EZ Form:
a. Line 26 — Please only include the surface area of the main pool (not the forebay)
at the permanent pool elevation for this item. Please revise.
b. Line 27 — Similar to the above comment, the volume of the main pool should only
include the main pool and not the forebay. Please revise.
c. Line 28 — Excluding the sediment storage zone from the main pool volume
calculations will result in a smaller average depth of the main pool than what is
currently shown. Please revise.
d. Line 32, Column 3 — The plans do not indicate that section 3 of the wet pond has
a forebay. Please revise/clarify.
e. Line 35 — The sum of the provided design volumes only equals 92,563 cf whereas
the minimum required treatment volume is shown as 98,919 cf. Please revise.
f. Line 40 — The calculations indicate that the drawdown time for this wet pond is
2.2 days (52.81 hours) whereas the drawdown time is shown as 4.6 days. Please
revise. NOTE: Nothing was provided in Appendix G of the calculation booklet.
10. While not required, it is strongly recommended to more proportionately distribute the
forebays between the two main points of inflow into the proposed wet pond. This is not
required per the MDCs, but an "undersized" forebay will need more frequent
maintenance than a more appropriately sized forebay (and section 4 of the wet pond has
the room for an enlarged forebay).

11. Provide pdfs of all revisions, 2 hardcopies of revised plan sheets, 1 hardcopy of other
documents, and a response to comments letter briefly describing how the comments have
been addressed.
a. Pdfs must be uploaded using the form at:
https:,[/edocs.deq.nc.gov/Forms/SW-Supplemental-Upload
b. Hard copies must be mailed or delivered to the following address:
i. For FedEx/UPS:
Suzanne McCoy
512 N. Salisbury Street, Office 640K
Raleigh, NC 27604
ii. For USPS:
Suzanne McCoy
1612 Mail Service Center
Raleigh, NC 27699-1612
While it is not required, it is recommended that the off -site drainage from upstream properties
be diverted around the SCM since the Applicant cannot maintain control over the development
of property that they do not own. If the Applicant elects to account for off -site drainage, there
must be a recorded legal agreement in place between the Applicant and the Owner of the
upstream property in which the Owner of the upstream property agrees to record a deed
restriction limiting the minimum/maximum amount of BUA on the upstream property that will
be treated in the Applicant's SCM, the locations and sizes of access and drainage easements,
how construction and/or ongoing maintenance costs will be handled, maintenance responsibility,
a list of legal recourses available to each party should one party fail to hold up their end of the
agreement, and any other related legal issues.
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 December 8, 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 SW3210801 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
[e-mail] or [phone].

Sincerely,
)64)M4�
Jim Farkas
Environmental Engineer
Stormwater Program
cc: Mooresville Regional Office