SW3201201_Add Info_20210305

ROY COOPER
Governor
MICHAEL S. REGAN
Secretary
BRIAN WRENN
Director
Marc Momsen, PE
223 N. Graham Street
Charlotte, NC 28202
NORTH CAROLINA
Environmental Quality
March 5, 2021
Subject: Second Request for Additional Information
Stormwater Permit No. SW3201201
Union County Sheriffs Office
Union County
Dear Mr. Momsen:
The Division of Energy, Mineral and Land Resources (DEMLR), received a Stormwater
Management Permit Application for the subject project on February 3, 2021. A review of that
information has determined that the application is not complete. The following information is
needed to continue the stormwater review:
Prior Comment 13 — "Please delineate the wetlands on the plans or provide a note
stating that no wetlands exist. Provide documentation of the qualifications and identity of
the individual who made this determination (Section VI, 8m). " Section VI, 8 of the
Application lists items that need to be included in the plans. Please place this note on a
plan sheet.
2. Prior Comment 21.b.ii. — "Supplement-EZ Form, Drainage Areas Page, Drainage Area
1: " Please complete the information in this column. This column represents the drainage
area to the sand filter (whereas the "Entire Site" column represents the entire project site).
3. Prior Comment 21.b.ii.1. — "Supplement-EZ Form, Drainage Area Page, Drainage
Area 1, Line 17 — Based on this project's location, the design storm is 1.0 inches. " The
design storm value should be recorded in the "Drainage Area 1" column, not the "Entire
Site" column.
4. Prior Comment 21.b.ii.2. — "Supplement-EZ Form, Drainage Area Page, Drainage
Area 1, Line 18 — The design volume should be based on the design storm. Since this
SCM is a sand filter you may reduce the design volume by 25% (In accordance with Sand
Filter MDC 3). " The design volume value should be recorded in the "Drainage Area 1"
column, not the "Entire Site" column. The design volume for State requirements is based
on the design storm (1.0"), not the maximum amount of treatment storage provided in the
D EQ �� 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
NORh1 CAROIJNA �
919.707.9200

sand filter. The design volume for this SCM appears in the calculations as the adjusted
water quality volume, this value should be used for the design volume.
5. Prior Comment 21.b.ii.3. — "Supplement-EZ Form, Drainage Area Page, Drainage
Area 1, Line 19 — Please use either the Simple Method or the Discrete NRCS Method to
calculate the design volume. More information can be found in Part B of the Stormwater
Design Manual. " The calculation method value should be recorded in the "Drainage
Area 1" column, not the "Entire Site" column. Per the calculations, the design volume
(adjusted water quality volume) appears to be calculated using the Simple Method.
6. Prior Comment 21.c.i. — "Supplement-EZ Form, Sand Filter Page, Line 2 — See earlier
comment. " As mentioned earlier, the design volume (adjusted water quality volume)
should be used for this item. Lines 23 & 30 will show the actual total treatment volume
provided by the SCM.
7. Prior Comment 21.c.iii. — "Supplement-EZ Form, Sand Filter Page, Lines 23 & 30 —
These volumes should only take into consideration the provided storage below the invert
of the lowest filter bypass (3" orifice) elevation. " Per the provided stage storage table, the
total amount of storage provided below elevation 535 ft is 12,165 cf. the bypass elevation
for the sand filter is at elevation 534.9 ft, therefore, the total volume that can be retained
in the sediment and sand chambers (Lines 23 + 30) must be less than 12,165 cf (The
values of both Line 23 & Line 30 are larger than this value). Please revise. Also, if the
storage volume provided below elevation 534.9 ft is interpolated from the provided stage -
storage table, an insufficient treatment volume (less than 11,120 cf) is provided. Please
either adjust the sand filter design so that sufficient treatment volume is provided below
the lowest bypass elevation or provide calculations showing that sufficient storage is
being provided.
8. Prior Comment 21.c.iv. — "Supplement-EZ Form, Sand Filter Page, Lines 26 & 32 —
Please separate the stage -storage table for the sand filter into sediment chamber and
sand chamber so that this information and Lines 23 & 30 can be verified. " The surface
areas shown in the Supplement-EZ Form do not match the values shown in the stage -
storage table. For example, the sediment chamber area is shown as 11,605 sf in the
Supplement-EZ Form, and 8,977 sf in the stage -storage table. The sand chamber area is
shown as 2,550 sf in the Supplement-EZ Form & plans, and 2,558 sf in the stage -storage
table. Please revise for consistency.
9. Prior Comment 22.a. — "Provide pdfs of all revisions... Pdfs must be uploaded using the
form at: https://edocs.deg.nc.gov/Forms/SW Project Submittal" Electronic copies of the
resubmitted items were not provided. Please make sure that all updated/corrected items
get electronically uploaded.
10. Please correct the following items on the Supplement-EZ Form:
a. Drainage Areas Page, Entire Site column:
i. Line 6 — This line is used when there is a subdivision of the property and
each lot is allocated a certain amount of BUA. Since this project does not

involve the subdivision of the property, this line should not be used (Line
7 is for New BUA that is located outside of subdivided lots). NOTE: The
value is correct, it is just located in the wrong spot.
ii. Line 10 — Please provide these values. This is a breakdown by type of the
new BUA (Line 7, the items of Line 10 should add up to Line 7).
iii. Line 14 — This item is not needed since the existing BUA predates the
State post -construction rule implementation in this location. The existing
BUA is not covered under a permit (since it predates the program) so it
should not be reported on this line (This line is usually used for project
modifications). NOTE: Lines 13 & 15 are correct and do not need to be
changed.
11. Please provide calculations showing that the outlet of the sand filter is stable for the 10-
year storm event (General MDC 4). It is noted that riprap sizing calculations are provided
for the "BMP Outfall", however it is unclear where the peak flow value (6.54 cfs) came
from (Also, the outfall of the sand filter appears to be some sort of level -spreader type
device, if that is the case, the provided riprap sizing calculation would not be appropriate
to demonstrate compliance). Please also provide calculations showing that the inlet is
protected from erosion from stormwater discharges (General MDC 4).
12. Provide pdfs of all revisions, 2 hardcopies of revised plan sheets, and 1 hardcopy of other
documents.
a. Pdfs must be uploaded using the form at:
https://edocs.deq.nc.gov/Forms/SW—Project Submittal
b. Hard copies must be mailed or delivered to the following address:
Jim Farkas
512 N. Salisbury Street
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 April 4, 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 SW3201201 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,
V- "I
Jim Farkas
Environmental Engineer
Stormwater Program
cc: Mooresville Regional Office