20131200 Ver 6_TIEC response letter #2 to DWR NOV 2020-SS-0014_20200818

Odom
Engineedngpuc
0
August 18, 2020
Mr. Andrew W. Moore P.G.
North Carolina Department of Environmental Quality
Division of Water Resources
Asheville Regional Office
2090 U.S. Hwy 70
Swannanoa, North Carolina 28778
Dear Mr. Moore:
169 Oak Street • Forest City, NC 28043
office 828.247.4495 • fax [phone]
Re: Response #2 - NOV 2020-SS0044
Project: Tryon International Equestrian Center
Address: 4066 Pea Ridge Road
Mill Spring, NC 28756
Regarding your email dated August 17, 2020 concerning the energy dissipator stabilization narrative /
construction detail and your request for additional information. We offer the following response on behalf of Tryon
International Equestrian Center.
1. We have considered use of rip rap for repair on the natural ground that was damaged by the storm event of May
2020. 1 have two concerns with rip rap material in this area; 1) the steepness of grade (40%) from end of existing
dissipator to edge of the stream bed and 2) the ability to prevent the potential displacement of the repair materials.
In my opinion, the placement of design classification D50— rip rap per the design manual at design CFS would not
provide adequate weight and likely be displaced to the stream. The weight of a single modular concrete block unit is
2475 lbs. and in my opinion the best application for this situation. The transfer of energy from the stepped modular
concrete block surfaces decreases as stormwater passes over each step.
2. The first modular concrete block row will be constructed to join the existing rock toe at an elevation (12") higher
than and flush with the rock toe to allow flow onto and over the rock toe not behind or below. Any voids between the
rock toe boulders currently embedded (12") below streambed elevation and the first row of modular concrete blocks
will be "chinked" with smaller rock material to fill gaps.
Work to correct the violations previously noted is in process and we look forward to working with you to resolve
these matters in very timely fashion. Please feel to contact me if you have any questions concerning this submittal.
Sincerely,
a a il--
David Odom, P.E.
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ODOM ENGINEERING, PILLC
169 Oak St., Forest City,
North Carolina, 28043
http.-Ilwww.odomengineering.com