SW3221008_Add Info_20230119

"STATE aFA'
°E
ROY COOPER 5 A
Governor
ELIZABETH S.BISER L,z.
Secretary
DOUGLAS R.ANSEL NORTH CAROLINA
Interim Director Environmental Quality
January 19, 2023
Civil &Environmental Consultants, Inc.
Attn: Mason L. Greeson, PE
3701 Arco Corporate Drive, Suite 400
Charlotte, NC 28273
AND
JCH NC, LLC
Attn: Robert Kreisher, Vice President
414 Turtleback Ridge
Weddington, NC 28104
Subject: Request for Additional Information
Stormwater Permit No. SW3221008 (Formerly SW3210802)
The Estates of Marvin Branch
Union County
Dear Mr. Greeson and Mr. Kreisher:
The Division of Energy, Mineral and Land Resources (DEMLR), received a Stormwater
Management Permit Application for the subject project on October 21, 2022. A review of that
information has determined that the application is not complete. The following information is
needed to continue the stormwater review:
1. SW3210802 Prior Comment 1 — "The SCM must meet all of the applicable MDCs of an
SCM per I5A NCAC 02B .0602(b). The provided detention basin is not an SCM, the
information for this "SCM" was not provided in the Supplement-EZ or O&M Agreement
Forms, and sufficient design calculations demonstrating that all of the MDCs were met
were not provided. Please ensure that the provided stormwater treatment device meets all
of the applicable MDCs for an SCM." As designed, the infiltration SCM does not meet
all of the applicable MDCs:
a. Infiltration MDC 1 —The provided soil report does not indicate the soil infiltration
rate (A value of 0.55 in/hr was provided but it is unclear where this value came from).
b. Infiltration MDC 2—Per the information provided in the soils report, there is
insufficient separation between the bottom of the SCM and the SHWT. The soil
report indicates that the SHWT is at elevation 577.0' while the plans and other
D E Q�� North Carolina Department of Environmental Quality I Division of Energy,Mineral and Land Resources
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submittal materials indicate that the bottom of the SCM is at elevation 578.0'. Please
revise as needed. NOTE: The provided soils report does not satisfy the
"hydrogeologic evaluation that demonstrates that the water table will subside to its
pre-storm elevation within five days or less" portion of Infiltration MDC 2 since this
information was not mentioned in the report.
c. Infiltration MDC 4—Pretreatment does not appear to be provided and is required for
this SCM. Please revise as needed.
d. Infiltration MDC 5 —The provided design does not appear to dewater the design
volume within the stipulated timeframe. Per the provided documents, the design
volume of the SCM (DV) is equal to 15,419 cf(NOTE: The design volume of the
SCM must be used for this calculation, not just the minimum required treatment
volume), the provided infiltration surface area (SA) is equal to 5,695 sf, the
infiltration rate of the Soil (K) is equal to 0.55 in/hr(NOTE: It is unclear where this
value came from), and a factor of safety (FS) of 2.0 (This minimum factor of safety
ensures that the SCM will function properly). Rearranging Equation 2 in Part C-1 of
the Manual to solve for time results in a drawdown time of about 118 hours which is
larger than the maximum allowable of 72 hours. Please revise as needed.
2. SW3210802 Prior Comment 6— "The provided detail for the `culvert' swale does not
appear to match the calculations. The calculations indicate that the bottom with of this
swale is 6 ft while the detail shows a bottom with of 2-3 ft." Please clarify the details for
the proposed swales. Plan sheet C-3.0 shows the stormwater swale detail as having a
bottom width of 6 ft and 5:1 side slopes. The culvert swale appears to have side slopes of
3:1 (per the grading plans) as do the curb outlet swales. The curb cuts plan view detail on
this sheet indicates that the bottom width of the curb outlet swales is 1 ft wide whereas a
2 ft bottom width is required per 15A NCAC 02H .1003(2)(d)(iii). It is unclear which
cross-section or methodology is used to determine the 10-year design velocity in the curb
outlet vegetated areas. Please revise as needed.
3. The provided swale calculations appear to be off. For example, the provided calculations
for curb outlet swale 8 (CC#8) shows a drainage area of 0.68 ac (and a design flowrate of
2.59 cfs) however the Supplement-EZ Form shows a drainage area of 0.46 ac (and a
design flowrate of 1.75 cfs). These differences also lead to a discrepancy in design
velocities between the calculations (3.21 fps) and Supplement-EZ Form (2.82 fps). Please
revise as needed for consistency.
4. Please clarify how the actual velocity was determined for the curb outlet vegetated areas
as the calculations do not appear to have been provided.
5. Please correct the following issues with the Supplement-EZ Form:
a. Drainage Areas Page:
i. Line 2 or 4—Please include a drainage area for the Infiltration SCM (This form
was not set up with the Goose Creek Rules in mind so feel free to list it as either a
high- or low-density drainage area and explain in the Additional Information area
(Line 22) that the SCM is required to meet the Goose Creek Rules).

ii. New column for the drainage area to the Infiltration SCM—Please fill out the
information in this column.
b. Infiltration Page:
i. Line 2—Please include the minimum required treatment volume. This is the
difference between the pre- and post-development 1-year 24-hour storm volumes.
ii. Line 8—This item is required per General MDC 5 and appears to be provided in
the form of the emergency spillway.
iii. Line 13 —Please answer this item as it is required per General MDC 10. If the
SCM is not located on a single-family lot, you can answer 'N/a'.
iv. Line 20—Please elaborate on the type of pretreatment provide in the Additional
Information section (Line 46).
v. Line 25 —This item does not appear to have been provided.
vi. Line 26—It is unclear where this value came from.
vii. Lines 32-43 —This SCM configuration appears to be that of an infiltration trench
instead of an infiltration basin (The main difference between the two being that
trenches contain stone or some other material in the storage area while basins do
not). Please complete Lines 34-43.
viii. Line 45 —Please revise as needed.
c. Low-Density Page:
i. Line 4—Please answer this item. If multiple side slopes are used, please elaborate
in the Additional Information section (Line 15).
ii. Line 7—Please revise to reflect the maximum slope value from the swale design
table.
iii. Swale design table—Please include the design information for"swale" (curb outlet
vegetated area) 5.
6. 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:
Jim Farkas
512 N. Salisbury Street, Office 640M
Raleigh, NC 27604
ii. For LISPS:
Jim Farkas
1612 Mail Service Center
Raleigh, NC 27699-1612
iii. Hand Delivery:

Please reach out to me prior to hand delivering a submission to make sure that I
(or someone else in my group) will be able to receive the submission. Do not
leave the package in the foyer with the security guard.
NOTE: Hard copies should not be sent to a Regional Office. Doing so will delay
the review process and the submission package may be lost while being sent from
the Regional Office to me in the Central Office.
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 February 18,2023, 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 SW3221008 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(919) 707-3646.
Sincerely,
Jim Farkas
State Stormwater Engineer
DEMLR Post-Construction Stormwater Program
cc: Mooresville Regional Office