SW3240102_Response To Comments_20240816

August 1, 2024
Response Comments August 15, 2024
Mc2 Engineering, Inc.
Attn: Jeff McCluskey, PE
2110 Ben Craig Drive, Suite 400
Charlotte,NC 28262
AND
Lane Creek Volunteer Fire Department
Attn: Chief Robert Sweatt
7608 Landsford Road
Monroe,NC 28112
Subject: Request for Additional Information
Stormwater Permit No. SW3240102
Lanes Creek Volunteer Fire Department
Union County
Dear Mr. McCluskey and Chief Sweatt:
The Division of Energy, Mineral and Land Resources (DEMLR), received a Stormwater
Management Permit Application for the subject project on January 31, 2024. A review of that
information has determined that the application is not complete. The following information is
needed to continue the stormwater review:
1. Please revise the Supplement EZ form.
a. Low Density Page
i. Line 4: This is the side slope of swales listed in below swale table.
This has been updated to call out the proposed side slopes of 3:1 as illustrated on
the grading plan.
ii. Line 5: This is the largest Vactual value listed in the below swale table.
This has been updated to call out the calculated maximum channel velocity
which is 1.19 ft/sec
2. Previous comment,unaddressed: 15A NCAC 02H.1003(2)(b) — The proposed design
does not maximize dispersed flow through vegetated areas/minimize the channelization of
flow. The runoff from the project is channelized via a pipe network of roof drains. A low-
density project would be designed so that most, if not all of the runoff from proposed
BUA is allowed to sheet flow across vegetated areas as dispersed flow.
Per our phone conversation and as indicated in the Supplement EZ#14 and#15 we are
requesting a variation to rule .1003. As previously indicated, there is flooding with the property
which has necessitated the need for storm sewer to pipe the runoff away from the building that
normally wouldn't be allowed for a low-density project. The plan has been updated to shorten the

amount of installed pipe to the minimal length by crossing the parking lot perpendicular. The
drainage area to Channel#1 which is the swale leading from the level spreader to the south towards
Landsford Road consists of.22 acres discharging from the pipes behind the building and 0.30 acres
of sheet flow from the parking lot and lawn/pasture.
15A NCAC 2H .1003(2)(b): DISPERSED FLOW. Projects shall be designed to
maximize dispersed flow through vegetated areas and minimize channelization of flow.
The proposed plans shall utilize a perforated slotted drain installed with a 0% slope so
that the runoff can be released as a level spreader into the vegetated swale (channel#1).
Under low flow conditions the rainwater will exit the perforated pipe into the
surrounding stone and soil and under higher flow conditions the water will fill the pipe
and then spill out from the top of the slotted drain in an even dispersed flow.
15A NCAC 2H .1003(2)(c): VEGETATED CONVEYANCES. Stormwater that cannot
be released as dispersed flow shall be transported by vegetated conveyances. A minimal
amount of non-vegetated conveyances for erosion protection or piping for driveways or
culverts under a road shall be allowed by the permitting authority when it cannot be
avoided.
In order for a project to meet low density requirements, the dispersed flow requirements
and BUA threshold requirements must be met. If proposing a pipe network within a low
density project, a variance can be applied for if it can be shown that the design meets or
exceeds the requirements. 15A NCAC 2H .1003 (6) VARIATIONS FROM THIS
SECTION. The permitting authority shall have the option to approve projects that do not
comply with all of the provisions of this Section on a case-by-case basis as follows: (b)
"If the variation pertains to other aspects of the project, then the applicant shall
demonstrate that the project provides equal or better stormwater control and equal or
better protection of waters of the State than the requirements of this Section."
At the point that the stormwater leaves the site, engineering calculations will need to be
provided to demonstrate compliance with 15A NCAC 2H .1003 (5) STORMWATER
OUTLETS. "Stormwater outlets shall be designed so that they do not cause erosion
downslope of the discharge point during the peak flow from the 10-year storm event as
shown by engineering calculations."
The proposed plan provides an 18' wide x 100' long vegetated buffer from the discharge of
the level spreader. The proposed 2% slope is very gentle and has a calculated maximum velocity
of 1.19 ft/sec far below the allowable velocity of 4.5 ft/sec based on the soil type and slope. The
total buffer from the discharge of the level spreader to the nearest downstream stream is 190'.