2022-05-25_BR-0076_Status_Mtg_05_Summary

5/26/2022

This summary covers the 5th in a series of recurring meetings which took place 5/25/22 at 1:00 p.m. via Microsoft TEAMS.

PARTICIPANTS:
Stacy Oberhausen NCDOT/TGS – Division 14 – Project Manager
Cheryl Knepp NCDOT – EAU- Bio Surveys

Kevin Mitchell NC DEQ, Division of Water Resources – Environmental Specialist

Crystal Amschler USACOE, Project Manager, Asheville Regulatory Field Office

Allyson Connor USFS, Land Management Planner

David McHenry NCWRC – Western DOT Coordinator

Jay Twisdale TGS – GESC Hydraulic Review
Paul Fisher TGS – GESC Hydraulic Review

John Williams RK&K – Planning / Project Manager
Cathy Houser RK&K – Roadway Design
Brent Huskey RK&K – Hydraulics Design

TROUT CONCERNS
Prior to the meeting Dave McHenry of NCWRC had asked about ways to minimize the impact of the culvert to the trout stream. NCDOT conducted a study of using rock plating to accomplish
the minimization. Dave requested that we discuss this study and minimization in general as a part of this meeting. Dave noted that the existing culvert is likely a barrier at low
flow, or at least an impediment. The proposed work will eliminate a large portion of the trout water in this system. The system is currently only occupied to approximately 1500 feet
upstream due a natural fall.

CULVERT LENGTH PRESENTATION
John Williams presented a series of slides (also included in e-mail distribution) which illustrated a standard 2:1 and a rock plated 1.5:1 slope to evaluate if minimization is possible.
The illustrations demonstrated that through most of the area affected by the culvert, the 1.5:1 did not achieve any more than the 2:1 slopes for the stream.

CULVERT LENGTH DISCUSSION
Question 1: Could a retaining wall work to shorten the upstream end of the culvert. This was ultimately in the context of addressing the issue now and not having to address it during
the 404/401 stage of the project. John responded that maybe at the southern end of the project where the retaining wall was short

it could work but that for the bulk of it, a retaining wall at the top of the slope could not work because construction of the wall could not be done while maintaining two lanes of traffic.

Question 2: Does two lanes of traffic have to be maintained? A signalized one-lane two-way detour only works when it happens on a straight section of roadway those waiting at the light
can see when all traffic is clear and it is safe to proceed. In this case, the location of the culvert is on a sharp curve with a mountainside blocking the line of sight where the one-lane
two-way detour would need to be.

Question 3: Could a retaining wall be built mid-slope? Geotechnical staff was not present during the meeting and NCDOT will follow up with that staff to further answer the question.
The hydraulics staff who were present responded that the bottom of the slope would have to be above the 100-year flood plain or else risk failure by scour. NCDOT agreed to follow up
on the question of a mid-slope retaining wall and to report back to this group. Enough information should be included to either demonstrate where a wall is or isn’t feasible with explanations
why as well as costs for the areas where it is feasible. If is a factor considered, the Army Corps and NCWRC both noted that the mitigation cost of $1200/ft of mitigation would need
to be considered.

Question 4: Could the downstream end be shortened? NCDOT agreed to provide feedback on the feasibility of connecting the end wall of the bridge to the culvert as a means of possibly
shortening it.

CULVERT STUDY REPORT DISCUSSION
The Culvert Study Report (CSR) was shared with the group ahead of the meeting. Dave McHenry expressed particular concern about the left barrel which was illustrated in the CSR as being
flat bottomed. He asked about possibly burying that barrel and including baffles to retain natural bed material to encourage fish passage as had been done in Watauga 87 and he provided
the CSR for that project (see attached) NCDOT agreed to study a culvert cross section including an 18” barrel with baffles on the right and a 12” barrel with baffles on the left for
both the up an downstream extensions of the culvert.

The scenario will need to be evaluated for hydraulic conveyance. Assuming it works hydraulically, the recommendations will be included. NCWRC, DWR, ACOE and USFS all agreed that this
solution would adequately address the problem of the culvert bottom. If the evaluation indicates a problem hydraulically, NCDOT will revisit the issue with the group.

BR-0076: NCDOT/Agencies Status Meeting– 5/25/22 Meeting Summary
Bridge No. 9 on NC 28 over Little Tennessee River
Division 14 – Graham/Swain County Line, NC