20131200 Ver 5_More Info Received_20170718

Burdette, Jennifer a
From: Kaylie Yankura <[e-mail]>
Sent: Tuesday, July 18, 2017 10:02 AM
To: Burdette, Jennifer a
Cc: Clement Riddle; [e-mail]; David Odom
Subject: Tryon International Equestrian Center - Request for Additional Information; Written
Response 7.17.17
Attachments: DWR Response Letter & Attachments - 071817.pdf
Jennifer,
Please see the attached written response to the DWR request for additional comments regarding the Tryon International
Equestrian Center. A hard copy is in the mail as well.
Thank you,
Kaylie
32 Clayton Street
Asheville, NC 28801
Office: 828-698-9800
Mobile: [phone]
kaylie(cD.cwenv.com

Odom
Engineering Puc
July 17, 2017
NC Division of Water Resources
401 & Buffer Permitting Branch
1617 Mail Service Center
Raleigh, NC 27699-1617
Attn: Jennifer Burdette
Re: Tryon International Equestrian Center
Request for Additional Information
Dear Ms. Burdette:
169 Oak Street • Forest City, NC 28043
office 828.247.4495 • fax [phone]
In response to your Request for Additional Information, dated July 12, 2017, please review the
following:
Although Session Law 2017-10 removed the Division's 401 Water Quality Certification
(WQC) requirement for on-site stormwater control measures to provide protection of
downstream water quality standards, it does not apply retroactively to projects or portions of
projects that were required to have a stormwater management plan (SMP) as a condition of a
previously approved 401 WQC. On April 10, 2015, the Division of Energy, Mineral and Land
Resources (DEMLR) approved a SMP as part of the 401 Water Quality Certification issued
February 17, 2014, to Tryon Equestrian Center for the first phase of the project. Prior to
receipt of your response to the Division's request for additional information, this office
believed that these revisions were underway based on consultation with Annette Lucas in
DEMLR. Your response indicated that the overall site is no longer subject to stormwater
management rules and shows that the wetland pond/level spreader for Area 7 (White Horse
Inn Area in the modification request) in the approved SMP will not be constructed and a
parking lot is now proposed in that location. The first phase of this project is required to meet
the conditions of the 401 WQC that was issued for this area. Therefore, you are obligated to
treat stormwater from the amount of built upon area (BUA) included in the approved SMP.
New BUA proposed within the first phase of the project does not require the same level of
treatment requ ired by the approved SMP. However, provide calculations to show that the
new BUA will not cause failure of the existing stormwater control measures (SCM) or SCM(s)
proposed to replace the wetland pond/level spreader. An equivalent amount of treatment of
new BUA within any of the high-density areas is acceptable in lieu of treating BUA required by
the approved SMP if it's not possible to treat the BUA as required by the approved SMP with
the new development plan. [15A NCAC 02H .0506 (b)(5)]
• A new wet pond will be constructed at the Salamander Hotel to replace the pond/level
spreader for Area 7. In the SMP dated April 10, 2015, Drainage Area 7 is shown to have an
impervious area of approximately 3.61 acres. The new wet detention pond shown will
treat a drainage area with approximately 3.87 acres

Odom
Engineering Puc
169 Oak Street • Forest City, NC 28043
office 828.247.4495 • fax [phone]
2. For portions of the project that are outside of the first phase of the project, provide
calculations used to determine that the flows will be at non-erosive velocities based on the land
cover receiving the discharge or will not overwhelm the receiving streams and cause erosion
where direct discharges are proposed. We suggest using the NC Erosion and Sediment Control
Planning and Design Manual, Chapter 8 (Appendices) for non- erosive velocities based on the
receiving land cover and NRCS National Engineering Handbook, Part 654.
• Calculations are attached to this letter showing discharge velocities for the respective
outlets.
Stream Restoration Design, Threshold Channel Design for stream channels. Links to these
references will be emailed to the project consultant and engineer for their convenience. [15A
NCAC 02H.0506 (b)(3) & (4)]
• Please see the attached calculations for the outlets at each of these locations. The locations,
culvert size, and slope has been added to the attached revised drawings. The riprap apron
sizes for each is shown in the table "Channel Outlet Protection" in the calculations. The
calculations for each of the culverts show the low velocities of these low slope sections.
4. The conceptual stormwater plan for the Salamander Hotel directs stormwater runoff to
the northwest and southwest corners of the site. A discharge is not proposed for the stream
channel due west of the facility. In addition to the information requested in Item #2, explain
how the hydrology of this stream channel will be maintained if stormwater from the stream's
watershed is diverted away. [15A NCAC 02H.0506 (b)(3) & (4)]
• The drainage from the pool area and roof drains will be diverted to this stream channel to
maintain the existing hydrology. The existing drainage area above the head of the small
stream is 6.08 acres. For the 25 -year storm, that will generate 10.4 cfs. The area to be
directed to the stream is 2.73 acres, however, with the construction of impervious area, the
25 -year storm will generate 11.7 cfs.
PRE -DEVELOPMENT 25 -YR RUNOFF
Drainage Area (Ac)
I (in./hr.)
C
Q (cfs)
6.08
8.56
0.2
10.4
POST -DEVELOPMENT 25 -YR RUNOFF
Drainage Area (Ac)
I (in./hr.)
C
Q (cfs)
2.73
8.56
0.5
11.7
5. The proposed plans indicate the culvert leading to the rip rap outlet downstream of the
proposed barns will be installed at a 0.5%slope. Explain how this slope will be achieved based
on topography which appears to show an approximately 50' elevation change over
approximately 120' horizontal feet. [15A NCAC 02H.0506 (b)(3) & (4)] This proposed
stormwater culvert also appears to cross a gas line right-of-way. Is this type of infrastructure
allowed within a natural gas line right-of-way?

Odom
Engineering Puc
169 Oak Street • Forest City, NC 28043
office 828.247.4495 • fax [phone]
Please see the attached storm drain profile to show how this elevation change is achieved.
This same type of storm drain has already been installed within a natural gas right-of-way on
this property and is allowed.
Please contact me if you need any additional information.
Thank you,
t --
David Odom, P.E.

STORMWATER CALCULATIONS
7.7:1
TRYON INTERNATIONAL EQUESTRIAN CENTER
Tryon, North Carolina
July 17, 2017

Odom
Engineering
PLLC
NC FIRM# P-0880
169 Oak Street
Forest City, N.C. 28043
828-247-4495

Channel Report
Hydraflow Express Extension for Autodesk® AutoCAD® Civil 3D® by Autodesk, Inc.
Stablehouse Inn Outlet
Circular
Diameter (ft)
= 5.00
Invert Elev (ft)
= 895.00
Slope (%)
= 0.01
N -Value
= 0.013
Calculations
Compute by:
Known Q
Known Q (cfs)
= 26.60
Elev (ft)
901.00
900.00
899.00
898.00
897.00
896.00
895.00
894.00
0
Section
Highlighted
Depth (ft)
Q (cfs)
Area (sqft)
Velocity (ft/s)
Wetted Perim (ft)
Crit Depth, Yc (ft)
Top Width (ft)
EGL (ft)
Culvert #1
1 2 3 4 5 6
Reach (ft)
Monday, Jul 17 2017
= 4.20
= 26.60
= 17.62
= 1.51
= 11.60
= 1.43
= 3.66
= 4.24
Depth (ft)
6.00
5.00
4.00
3.00
2.00
1.00
0.00
-1.00
7

Channel Report
Hydraflow Express Extension for Autodesk® AutoCAD® Civil 3D® by Autodesk, Inc.
Village Outlet
Circular
Diameter (ft)
= 6.00
Invert Elev (ft)
= 905.00
Slope (%)
= 0.01
N -Value
= 0.013
Calculations
Compute by:
Known Q
Known Q (cfs)
= 37.20
Elev (ft)
912.00
911.00
910.00
909.00
908.00
907.00
906.00
905.00
904.00
0
Section
Highlighted
Depth (ft)
Q (cfs)
Area (sqft)
Velocity (ft/s)
Wetted Perim (ft)
Crit Depth, Yc (ft)
Top Width (ft)
EGL (ft)
Culvert #2
1 2 3 4 5 6 7
Reach (ft)
Monday, Jul 17 2017
= 4.36
= 37.20
= 22.06
= 1.69
= 12.27
= 1.60
= 5.34
= 4.40
Depth (ft)
7.00
6.00
5.00
4.00
3.00
2.00
1.00
0.00
-1.00
8

Culvert Report
Culvert #3
Hydraflow Express Extension for Autodesk® AutoCAD® Civil 3D® by Autodesk, Inc.
Monday, Jul 17 2017
White Horse Inn Outlet (Culvert #4)
Invert Elev Dn (ft)
= 845.49
Calculations
Pipe Length (ft)
= 50.00
Qmin (cfs)
= 0.00
Slope (%)
= 0.50
Qmax (cfs)
= 92.00
Invert Elev Up (ft)
= 845.74
Tailwater Elev (ft)
_ (dc+D)/2
Rise (in)
= 36.0
Shape
= Circular
Highlighted
Span (in)
= 36.0
Qtotal (cfs)
= 10.00
No. Barrels
= 2
Qpipe (cfs)
= 10.00
n -Value
= 0.013
Qovertop (cfs)
= 0.00
Culvert Type
= Circular Concrete
Veloc Dn (ft/s)
= 1.09
Culvert Entrance
= Square edge w/headwall (C)
Veloc Up (ft/s)
= 3.99
Coeff. K,M,c,Y,k
= 0.0098, 2, 0.0398, 0.67, 0.5
HGL Dn (ft)
= 847.34
HGL Up (ft)
= 846.44
Embankment
Hw Elev (ft)
= 846.68
Top Elevation (ft)
= 855.00
Hw/D (ft)
= 0.31
Top Width (ft)
= 0.00
Flow Regime
= Inlet Control
Crest Width (ft)
= 0.00
El -(R)
857.00
a55.00
8630❑
851 00
a49 ❑0
847.00
945 on
943 on
<Name7
Hw Depth (R)
11.26
9.26
726
526
5 10 15 20 25 30 35 40 45 50 55 60 65
Ci -1w Calvert HGL Embank
326
1.26
-074
-274
70
Reach (R)

Channel Report
Hydraflow Express Extension for Autodesk® AutoCAD® Civil 3D® by Autodesk, Inc.
Salamander Hotel Outlet
Circular
Diameter (ft)
= 5.00
Invert Elev (ft)
= 850.00
Slope (%)
= 0.01
N -Value
= 0.013
Calculations
Compute by:
Known Q
Known Q (cfs)
= 23.00
Elev (ft)
856.00
855.00
854.00
853.00
852.00
851.00
850.00
849.00
0
Section
Highlighted
Depth (ft)
Q (cfs)
Area (sqft)
Velocity (ft/s)
Wetted Perim (ft)
Crit Depth, Yc (ft)
Top Width (ft)
EGL (ft)
1 2 3 4 5 6
Reach (ft)
Culvert #4
Monday, Jul 17 2017
= 3.65
= 23.00
= 15.37
= 1.50
= 10.25
= 1.33
= 4.44
= 3.68
Depth (ft)
6.00
5.00
4.00
3.00
2.00
1.00
0.00
-1.00
7

CHANNEL OUTLET PROTECTION
Channel #
Flow (cfs)
Wetted
Perimeter
Dia (ft)
d50 Riprap
Size (ft)
Riprap Width at
Pipe Outlet (ft)
Apron
Length (ft)
Apron Width
at End (ft)
Culvert 1
26.6
11.6
1
12
21
33
Culvert 2
37.2
12.27
1
13
21
34
Culvert 3
92
18.28
1
19
21
40
Culvert 4
23
10.25
1
11
21
32

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ph: 828.247.4495 fax: [phone]
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JOB NAME: TRYON INTERNATIONAL EQUESTRIAN CENTER SCALE: 1 200'
LOCATION: TRYON, N.C.
DESCRIPTION: WHITE HORSE INN AND COVERED
ARENA BARNS STORMWATER MANAGEMENT SYSTEM
- DATE 06/05/17
ZZVF//-/ 1 —7'--`--- 'Qu —
DRAWN BY: JCW
CHECKED BY: DWO
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PROJECT NUMBER I SHEET
16120 14 OF 4�

910
900
890
880
870
860
850
840
830
0+
BARN STORM DRAIN PROFILE
CTA -�-4-dd -�7 _..._,.._ ___...._
Odom
Engineering
PLLC
169 Oak Street, Forest City, N.C. 28043
ph: 828.247.4495 fax: [phone]
P-0880
01ne uers
JOB NAME: TRYON INTERNATIONAL EQUESTRIAN CENTER

ARENA BARNS STORMWATER MANAGEMENT SYSTEM
910
900
:•8
880
)0% SLOPE
870
860
850
840
830
45
SCALE: 1" = 100' DRAWN BY: JCW
DATE: 06/05/17 CHECKED BY: DWO
PROJECT MGR: DWO
PROJECT NUMBER SHEET
16120 4 OF 40