SW3171201_Response To Comments_20230810

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ROY COOPER u 'I�, o
Governor ■r;¢'a �f
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ELIZABETH S.BISER ` ,,z.vs�
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Secretary
BRIAN WRENN NORTH CAROLINA
Director Environmental Quality
April 25, 2023
Bohler Engineering, NC, PLLC
Attn: Allen McDowell, PE
1927 S. Tryon Street, Suite 310
Charlotte, NC 28203
AND
LGI Homes NC, LLC
Attn: Jeff Webb, Authorized Officer
3037 Sherman Drive
Lancaster, SC 39720
Subject: Second Request for Additional Information
Stormwater Permit No. SW3220805
Village at Granite Quarry—Phase III
Rowan County
Dear Mr. McDowell and Mr. Webb:
The Division of Energy, Mineral and Land Resources (DEMLR), received a Stormwater
Management Permit Application for the subject project on January 25, 2023. A review of that
information has determined that the application is not complete. The following information is
needed to continue the stormwater review:
1. Prior Comment 2— "This project area appears to already be covered by permit
SW3171201." As indicated in the response to comments letter dated January 17, 2023,
you are seeking a modification to SW3171201 to account for the changes to that project
caused by this project. Please complete either a minor modification form (for changes to
SW3171201 that do not increase the BUA within the project area and do not increase the
size of the SCMs associated with that project) or a major modification (for changes to
SW3171201 that do not qualify as a minor modification). If applying for a minor
modification, please complete the minor modification form and provide the items
requested on the form (plus revised BUA tables from Section IV, 10 of the Application
and Supplement-EZ Form and any other revised permit items, such as revised project
limits). If applying for a major modification, the process is nearly identical to applying
for a new permit, however additional submittal items are required in accordance with
15A NCAC 02H .1042(2)(k) & (1).
We are seeking a major modification for BMP 6. Please reach out if this
does not make sense for this site.
DE Q North Carolina Department of Environmental Quality I Division of Energy,Mineral and Land Resources
,jt 512 North Salisbury Street 11612 Mail Service Center I Raleigh,North Carolina 27699-1612
NORTH CAROLINA
D¢pehnron pl Environmental Ouallry 919.707.9200

2. Prior Comment 3— "There appears to be an issue with the BUA accounting for this
project." I have attached additional guidance for filling in the BUA tables for this project
since it is somewhat unique. For a subdivision project, such as this one, "On-site
Buildings/Lots"/"New BUA on subdivided lots" refers to the BUA allocated to the
individual lots per the deed restriction document. Per the deed restriction document, the
individual lots are allocated a total of 96,080 sf of BUA. This should be reflected in the
entire site column of the Supplement-EZ Form and the drainage area columns (NOTE:
Since a low-density column is added to account for the project areas that do not drain to
an SCM, the on-site components of the 3 drainage areas will add up to the total project
area). For the "On-site Streets/Parking/Sidewalks/Other"/"New BUA not on subdivided
lots" these items refer to "common area" BUA that is not allocated to the individual lots
(such as roadways, mail kiosks, clubhouses, etc...)The BUA allocated to the individual
lots should not be double counted in these items. "Future" BUA refers to BUA that will
be built at some future point in time. It is recommended to include a brief description of
any future BUA uses/allocations in the Additional information section of the
Supplement-EZ Form. "Off-site" BUA refers to BUA that is located outside of the
project area and is draining to an SCM located within the project area(For example, any
BUA located within the Phase I area or within NCDOT ROW that drains to SCM#6
would be considered as "Off-site BUA". "Existing BUA"refers to BUA that already
existed on-site prior to the post-construction stormwater rules taking effect in this area
(July 1, 2007) and does not refer to BUA that was permitted after this date (BUA that was
permitted after the effective date of the rules is referred to as "New BUA" even if it was
previously permitted and has been in place for a few years, such as the Phase I BUA).
Deed restrictions revised and reflected on EZ form
3. Prior Comment 5 — "Please ensure that Runoff Treatment is being met by this project
(15A NCAC 02H.1002(43)). In order to meet Runoff Treatment, the net increase in BUA
from existing to proposed conditions must be captured/treated in one or more primary
SCMs and the submittal materials indicate that there will be some areas of BUA that are
bypassed. If these bypassed areas will be captured/treated by an off-site SCM(from
SW3171201) it needs to be indicated in the Supplement-EZ Form. If the bypassed BUA
will not and cannot be captured in an SCM, the bypass area can be permitted as a low-
density area (provided that it meets the requirements to be considered as a low-density
area). If the bypassed area does not meet the low-density requirements, a variance can be
sought in accordance with 15A NCAC 02H.1003(6)." As designed, the project areas that
are not draining to the SCMs do not meet the definition of low-density (15A NCAC
02H .1003(2)). Please either revise the design so that either the net increase in BUA for
this project is captured in one or more primary SCMs or so that the low-density bypass
area(s) meet the low-density design requirements or indicate that you would like to seek a
variance for this project (NOTE: For a variance to be approved, you must demonstrated
The low density areas located on-site do not have any proposed 'r
impervious areas only existing impervious per approved phase I plans.
4. Prior Comment 6d— "The provided drawdown calculations use a design volume of
approximately 13,486 cf between the permanent pool surface elevation (754.0') and the
invert of the bypass weir(755.6') however the provided stage-storage table for the
temporary pool indicates that approximately 19,000 cf of storage is provided between

these two elevations. Please revise as needed." This issue was not addressed. The
provided drawdown calculations indicate that the temporary pool will draw down from
elevation 755.6' to elevation 754.0' within 2.63 days at a rate of 0.053 cfs. 0.053 cfs *
2.63 days 12,000 cf which is less than the volume that can be provided between
elevation 755.6' to elevation 754.0' (z19,000 cf). Please revise the drawdown
calculations so that they are based on the temporary pool volume (volume provided
between elevation 755.6' to elevation 754.0', z19,000 cf), not the minimum required
design volume. Revised.
5. Prior Comment 6e— "As designed, the wet pond appears to short-circuit(Wet Pond
MDC 4)." Please provide a detail for the baffles and ensure that the baffles extend above
the temporary pool surface elevation (755.6'). Added.
6. Prior Comment 6h— "Please provide the area of the vegetated shelf so that the
provided planting density can be verified(Wet Pond MDC Jib)." Per the provided stage-
storage table, the cross-sectional area of the vegetated shelf(between elevations 554.0 &
555.0') is 2,762 sf(11,632 sf— 8,870 sf). Per the planting plan, the total amount of plants
for the vegetated shelf is 632 plants (214 + 197 + 221). This results in a plant density of
approximately 45.8 plants per 200 sf. Please revise. Revised.
7. NOTE: It is noted that the previously proposed sand filter has been removed from the
design. The previously issued comments with regard to this sand filter are now irrelevant.
8. Prior Comment 9bi— "If you are permitting the bypass areas as low-density areas,
please include the completed low-density page of the form." This information was not
provided and it is unclear if you are seeking a variance. These areas were approved in the
Phase I approved plans
9. Prior Comment 9bii— "Line 9—See earlier comment. Z his item refers to the total
amount of BUA that is allocated to the individual lots. This BUA should not be double
counted in Lines 10/12 and should correspond to the amount allocated to the individual
lots as shown in the Deed Restriction Form." See earlier comment, please revise. Revised.
10. Prior Comment 9biv— "Line 15—Existing BUA refers to BUA that was in place prior
to the rules going into effect, not the BUA that happens to be located on-site currently.
BUA associated with SW3171201 that is draining to SCMs associated with SW3220805
should just be listed in Line 11 as Off-site BUA." See earlier comment, please revise. Revised.
11. Prior Comment 9cix— "Line 34— The cleanout depth of the forebay is measured from
the permanent pool surface elevation to the excavated bottom of the forebay." My
apologies, there was an issue in the prior comment, it should read as follows, "Line 34—
The cleanout depth of the forebay is measured from the permanent pool surface elevation
to the top of the sediment storage zone in the forebay." The permanent pool surface
elevation is shown as 754.0' and the top of the sediment storage zone for the forebay is
shown as 752.0' (754.0' —752.0' = 2' = 24"). This also corresponds with the information
shown in the O&M Agreement Form. Revised.

12. Prior Comment 9cx— "Line 35—See earlier comment." The design volume of the SCM
is the volume that can be stored above the permanent pool (elevation 754.0') and below
the invert of the lowest bypass (elevation 755.6'). Per the Stage-storage table, this value
is approximately 19,000 cf. Please revise as needed. Revised.
13. Prior Comment 9cxii— "Line 40—See earlier comment." Please revise this item in
accordance with the earlier comment. Revised.
14. Prior Comment 9cxiii— "Lines 43 & 44—See earlier comment." While the depth to the
forebay entrance (Line 43) is shown to be larger than the depth to the forebay exit(Line
44), the values do not appear to be correct. The depth of the forebay is measured from the
permanent pool surface elevation to the excavated bottom of the forebay near the
entrance/exit of the forebay. For example, the permanent pool surface elevation is shown
at elevation 754.0' and the excavated bottom of the forebay near the exit is at elevation
751.5' (754.0' —751.5' = 2.5' = 30" and 24" is shown). Please revise as needed. Revised.
15. Please correct the following issues with the Application: Revised.
a. Section III—The permittee appears to have been changed from Jeff Webb to Tim
Thompson. Please either revert this to how it previously was or provide proof of
signatory authority (required per 15A NCAC 02H .1042(2)(b)(ii)) and a revised
Sections IX & X of the Application.
b. Section IV, 10, Drainage Area B6:
i. The sum of the on-site (247,857 sf) and off-site (16,553 sf) drainage areas do
not add up to the total drainage area (264,409 sf). This appears to be a
rounding error.
ii. The sum of the different BUA types (149,379 sf) does not correspond to the
provided value (145,429 sf). The % Impervious Area may need to be
recalculated. Please revise as needed.
c. Section IV, 10, Drainage Area B3:
i. The sum of the different BUA types (422,331 sf) does not correspond to the
provided value (459,843 sf). The % Impervious Area may need to be
recalculated. Please revise as needed.
d. Section IV, 10, Drainage Area LD:
i. The % Impervious Area(4872%) does not appear to be correct. The revised %
Impervious Area value appears to be in excess of 24% which exceeds the low-
density density threshold.
16. Supplement-EZ Form, Drainage Areas Page, Line 4 &LD Columns—A single low-
density drainage area should be used for this project (similar to how it is shown in the
Application) and include the portions of the project area that do not drain to an SCM
(from either SW3220805 or SW3171201). Revised.
17. Please provide a revied post-development drainage area map for the project. This item is
required per 15A NCAC 02H .1042(2)(g)(iv) and Section VI,8o of the Application.
Revised.

18. 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 640E
Raleigh, NC 27604
ii. For USPS:
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.
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, either the
off-site area can be assumed to be 100% BUA (its full build-out potential) or 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.
NOTE: Per Division policy, the next review of this application will be the final review. Failure
to provide the requested information will result in the project being returned as incomplete. The
return of a project will necessitate resubmittal of all required items, including the application fee.
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 25,2023,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 SW3220805 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,
V"VI G.1
Jim Farkas
Environmental Engineer
Stormwater Program
cc: Mooresville Regional Office