SW3210801_Add Info_20210826

ROY COOPER
Governor
ELIZABETH S. BISER
Secretary
BRIAN WRENN
Director
Brad Smith, PE
1020 Euclid Avenue
Charlotte, NC 28203
NORTH CAROLINA
Environmental Quality
August 26, 2021
Subject: Request for Additional Information
Stormwater Permit No. SW3210801
I-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 August 2, 2021. A review of that
information has determined that the application is not complete. The following information is
needed to continue the stormwater review:
1. Since all of the wet ponds are connected to each other via 0% slope pipes, we will treat
the entire configuration as a single pond for permitting purposes. Please revise the
submittal items to reflect a single wet pond. Compliance with the MDCs will be judged
based on the combined wet pond, not the individual sections.
2. This project appears to be located within 5 miles of the Mid -Carolina Regional Airport
(Section II, 5). Please revise as needed.
3. Please revise the stormwater treatment summary since there is only one wet pond in this
project (Section IV, 1). You should still mention the disjointed nature of this wet pond.
This is currently mentioned in the summary but should be tweaked to refer to a single wet
pond (maybe stating that the wet pond has 4 distinct sections or pools?).
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]
NOTE: The project area, not the property area, is used in this calculation. Also, existing
BUA may be excluded from the percent impervious calculations in accordance with 15A
NCAC 02H .1003(1)(b).
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 _
oepm nt of EnvimnmwUl uwl ry 919.707.9200

5. Please revise the number of drainage areas for this project to 1 since there is only one wet
pond in this project (Section IV, 9).
6. Please combine the drainage area information since there is only one wet pond in this
project (Section IV, 10).
7. Please initial the items on the submittal requirements checklist that are provided in this
submission (Section VI).
8. Please identify and delineate the on -site surface waters in the main set of plans (Section
VI, 8h). The surface water surface area information shown in Section IV, 6 of the
Application should be able to be verified on the plans.
9. Please identify and dimension all BUA in the main set of plans (Section VI, 8j). The
BUA information shown in Section IV, 10 of the Application and in the Supplement-EZ
Form should be able to be verified on the plans. It is noted that the BUA is dimensioned
on the plans, however, due to the irregular geometry of the BUA, verifying the amount of
BUA from the provided plans to a square foot precision is not practical (it would be if we
asked for or had the ability to view the CAD files, but we do not). You may wish to add a
BUA summary table similar to the ones in Section IV, 10 of the Application or the
Supplement-EZ Form.
10. Please delineate the drainage area to the proposed wet pond in the main set of plans
(Section VI, 8o).
11. Please provide some form of official documentation showing that the Signing Official for
the Applicant, Caleb Moore, has the authority to sign on the Applicant's behalf (Section
VI, 11).
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. Please provide stage -
storage tables for the forebays, main pools, and temporary ponding zones so that the
design can be reviewed. Since this wet pond is made up of four different sections, I
would recommend providing stage -storage tables for each section and a combined stage -
storage table for the entire wet pond. This would result in 4 forebay stage -storage tables
(1 for each of the three forebays in wet pond sections 1, 3, & 4 and 1 for the combined
forebay), 5 main pool stage -storage tables (1 for each of the four main pools in wet pond
sections 1, 2, 3, & 4 and 1 for the combined main pool), and 5 temporary ponding zone
stage -storage tables (1 for each of the four temporary ponding zones in wet pond sections
1, 2, 3, & 4 and 1 for the combined temporary ponding zone). The stage -storage tables
are required to ensure compliance with Wet Pond MDCs 1, 2, 3, 5, 6, & 7.
13. Please clarify the difference between the "Storage Elevation" and the "Basin Bottom" as
shown on the wet pond cross -sections. There must be at least 6 in of sediment storage
between the excavated bottom of the pond and the top of the sediment storage zone (Wet
Pond MDC 3). The way that it is currently shown on the plans, it appears as though the

excavated bottom of the pond (solid line) is above the sediment storage top elevation
(dashed line). Please see attached image.
14. Please clearly indicate the top of the sediment storage zone in the forebays in the cross -
sections. Wet Pond MDC 3 requires that the forebay and main pond have at least 6 inches
of sediment storage depth (The sediment storage top elevation should be at least 6 inches
above the excavated bottom of the forebay). Since the forebay entrance is deeper than the
exit (and the sediment storage elevation is typically constant) there will be more sediment
storage depth provided near the entrance than the exit (See attached image).
15. Untreated stormwater runoff entering the forebay of "wet pond 3" may short-circuit the
wet pond system since the flow distance from the inlet to the outlet of "wet pond 3" and
the flow distance from the inlet to the outlet of "wet pond 2" are both fairly short (Wet
Pond MDC 4). You may wish to consider adding berms or baffles or relocating some of
the inlets/outlets to increase the flow path through the system.
16. The 0% slope pipes connecting the sections of the wet pond should have trash racks or
other means of preventing large debris from entering and clogging these pipes (Wet Pond
MDC 10). It is also recommended to add emergency spillways to each of the sections of
the wet pond. It is noted that the wet pond is designed to contain the 100-year storm
event, but emergency spillways are still recommended to prevent embankment failures
during large storm events or if there is a malfunction (i.e. a clog) that prevents the outlet
structure from functioning as designed.
17. Please provide calculations showing that each inlet/outlet/0% slope pipe of the wet pond
system is stable (General MDC 4).
18. Please clearly show the stormwater maintenance access and easement in the main set of
plans (General MDCs 8 & 9). The entire footprint of the SCM system must be included
in the access and maintenance easement, plus an additional 10 feet (25 is recommended
for wet ponds) around the SCM to provide enough room to complete maintenance tasks.
This SCM system includes the side slopes, forebay, riser structure, SCM device, and
basin outlet, dam embankment, outlet, and emergency spillway. The easement should
extend to the nearest public right-of-way and should not include any slopes in excess of
3:1 (H:V).
19. Please clearly show the elevations of the top and bottom of the vegetated shelf on the
cross -sections of the wet pond in the main set of plans (15A NCAC 02H .1042(2)(h)).
20. Please correct the following issues with the O&M Agreement Form:
a. Please revise the cover page of the O&M Agreement Form to indicate a single
wet pond. The design summary page can be left as -is since the different sections
of the pond have different cleanout depths (you may wish to put a note on this
page of the form indicating that the wet pond has multiple sections).
b. Please provide an original, signed hard copy of this form.

c. Wet Detention Pond Design Summary Page — The pond design does not appear to
include a vegetated filter. A vegetated filter is typically placed downstream of the
outlet of the wet pond and allows the discharge to be dispersed (please refer to
Part C-9 of the Manual for more information).
21. Please correct the following issues with the Supplement-EZ Form:
NOTE: There may be other issues with the Supplement-EZ Form, but as mentioned
earlier, the entire design could not be reviewed for compliance with the MDCs.
a. Cover Page:
i. Line 2 — The project area should match the information shown in Section
IV, 7 of the Application. Revise as needed.
ii. Line 5 — This project appears to be a high -density project since it does not
meet the low -density design requirements outlined in 15A NCAC
02H .1003(2).
iii. Lines 7-9 — Vegetated setbacks are required from all on -site surface waters
per 15A NCAC 02H .1003(4) & .1017(10).
iv. Line 13 — Please revise the number of wet ponds to 1.
b. Drainage Areas Page:
i. Line 1 — As mentioned previously, this project does not meet the design
requirements of a low -density project and is therefore a high -density
project.
ii. Line 2 — Please revise the number of drainage areas to 1 since there is only
1 SCM.
iii. Line 3 — This project does not appear to have any low -density areas.
Please either correct this or clearly show the low -density area on the plans.
iv. Entire Site Column:
1. The entire site column should be an accounting of all of the BUA
that will exist within the project boundary (not necessarily just a
sum of the drainage area columns). For example, if there is any on -
site BUA that is located outside of the drainage area to the SCM,
this BUA would be accounted for in the entire site column.
2. 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. Please also make sure to show these values in square feet.
3. Line 18 — This value should correspond to the percent impervious
area value shown in Section IV, 8 of the Application.
4. Lines 19-20 — These items are not required for the entire site
column.
v. Drainage Areas Columns:
1. Please combine the drainage area columns into a single column
since there is only 1 SCM.
2. Lines 5-7 - Please make sure to show these values in square feet.
3. Line 12 - The surface area of the wet pond does not need to be
considered as impervious area.

4. Line 20 — The sum of these items (147,015 cf) does not equal the
design volume as shown in the calculations (111,241 cf). Revise as
needed for consistency.
c. Wet Pond Page:
i. Since the individual sections of the wet pond are not all designed exactly
the same, it is recommended to have a column for each section of the wet
pond (as shown in the provided Supplement-EZ Form) and a column for
the entire combined pond.
ii. Lines 20 & 21 — The information in the "wet pond 3" column and in the
"wet pond 4" column appear to be swapped (per the plan sheets). Please
ensure that the information in each column is correct for the specific
section of the wet pond.
iii. Line 28 — The average depth of the main pool (1.99 ft) is less than the
required 3.0 ft average depth per Wet Pond MDC 2. Also, the provided
average depth does not match the information shown in the calculations.
iv. Line 31 — The Supplement-EZ Form indicates that the permanent pool is
located halfway up the vegetated shelf, therefore the width of the
submerged portion of the vegetated shelf would only be 3.0 ft, not 6.0 ft.
v. Line 34 — The cleanout depth of the forebay is the distance between the
permanent pool elevation and the top of the sediment storage zone in the
forebay.
vi. Line 43 — The depth of the forebay at the entrance is the distance between
the permanent pool elevation and the forebay entrance as shown on the
cross -sections of the wet pond.
vii. Line 44 — The depth of the forebay at the exit is the distance between the
permanent pool elevation and the forebay exit as shown on the cross -
sections of the wet pond.
22. 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 LISPS:
Suzanne McCoy
1612 Mail Service Center
Raleigh, NC 27699-1612

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 September 25, 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,
Jim Farkas
Environmental Engineer
Stormwater Program
cc: Mooresville Regional Office