20131200 Ver 5_ARO Comments_20170710

Burdette, Jennifer a
From: Moore, Andrew W
Sent: Monday, July 10, 2017 2:22 PM
To: Burdette, Jennifer a
Cc: Price, Zan (George)
Subject: ARO Comments -Tryon Equestrian Center Individual Permit Modification Additional
Information Response dated June 12, 2017 (20131200 V5)
Jennifer,
The Asheville Regional Office has reviewed the subject submittal and is submitting the following summary of our review.
The majority of the ARO's comments submitted March 15, 2017, regarding the Individual Permit Modification were
addressed in the June 12, 2017 response. However, the ARO still has concerns regarding the proposed stormwater plan
and its potential to impact water quality.
On April 10, 2015, DEMLR approved a stormwater management plan as part of the 401 Water Quality Certification
issued February 17, 2014, to Tryon Equestrian Center for the first phase of the project. The 2015 approved stormwater
plan included a number of components and/or areas that are proposed for additional development and stream/wetland
impact in the Individual Permit application. Those components and/or areas include: a proprietary technology called
isolator row for Area 6 in the stormwater management plan (Covered Arena/Barns 7 and 8 areas in IP application); a
wetland pond/level spreader for Area 7 (Proposed White Horse Inn Area in IP application); and a stormdrain easement
area that extends into both Areas 6 and 7. The conditions of the 2015 stormwater management approval require that any
changes to the maximum allowable drainage area and the maximum impervious areas must be approved in a revised
stormwater management plan. Though the proposed maximum allowable drainage area and proposed impervious areas
were not provided in the stormwater plans submitted with the June 12, 2017 Individual Permit Request for Additional
Information Response, it appears that both will increase if the proposed impacts are approved. Therefore, it appears that
based on Condition 2 of the April 10, 2015 stormwater management approval plan, a new stormwater plan is required. It's
not clear to the ARO how Session Law 2017-10 affects the previously approved water quality certification, its associated
stormwater management plan, and the previously approved conditions of the stormwater management plan.
The proposed stormwater plan for this area is to discharge the collected stormwater to a rip rap outlet device just above
the existing stream channel. Note that the previously approved wetland pond/level spreader will be removed, as will the
stormdrain easement area in the approved stormwater management plan. It appears that a portion of the previously
approved isolator row will remain intact in this area, though it is not clear what portion of former Area 6 stormwater
would be routed to this treatment device and what portion would go to the rip rap outlet system. The majority of the
stormwater collected in former Areas 6 and 7 would not be retained for slow release. No stormwater control measures, as
presented in the NCDEQ Stormwater Design Manual or the 2H stormwater rules, are proposed for these areas. Overall, it
appears that the applicant is proposing to significantly increase the impervious area in this watershed and to significantly
decrease stormwater treatment.
The ARO is concerned that the lack of stormwater treatment coupled with the proposed stream impact may significantly
disrupt the hydrology of the receiving water and cause de -stabilization of the streambanks below the impact area and
stormwater discharge point as well as disruption to aquatic habitat. The ARO recommends that the applicant re -design the
stormwater treatment system in this area to include a slow release of stormwater to ensure no violations of water quality
standards in the receiving stream, or provide supporting data/calculations to demonstrate that the proposed stormwater
system will not result in water quality violations in the receiving stream.
The ARO has two additional notes regarding the proposed stormwater plan:

I . The proposed plans indicate the culvert leading to the rip rap outlet will be installed at a 0.5% slope. However, it
is not clear how this slope will be achieved based on topography which appears to show an approximately 50'
elevation change over approximately 120' horizontal feet.
2. The proposed stormwater culvert also appears to cross a gas line right-of-way. It seems unlikely that this type of
infrastructure would be allowed within a natural gas line right-of-way. Perhaps that gas line will be abandoned.
Feel free to contact me if you have any questions.
Andrew W. Moore, P.G.
Environmental Specialist —Asheville Regional Office
Water Quality Regional Operations Section
NCDEQ — Division of Water Resources
828 296 4684 office
email: [e-mail]
2090 U.S. Hwy. 70
Swannanoa, N.C. 28778
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