HomeMy WebLinkAbout20171018 Ver 1_Email_20180806Carpenter,Kristi
From: Thomson, Nicole J
Sent: Monday, August 06, 2018 2:47 PM
To: Eason, Patty P; David.E.Bailey2@usace.army.mil;
Norton, Apri) R; Elam, William H; Lee, Craig J; Dan
Duffield (dan.duffield@summitde.net)
(dan.duffield@summitde.net)
Cc: Parker, Jerry A; Patton, Vance H; Griffith, Aaron E;
Whitley, Kimball; Harper, Aaron A; jodyandrews4
@gmail.com; Robinson, Stephen J
Subject: B-5239, Bridges 119 and 126 on NC 87 over the Haw
River and Mill Race (respectively)
Attachments: B-5239 August 6 2018 site review.docx; 08_06_l8
report pic location.pdf; below Haw River Damjpg
Follow Up Flag: Follow up
Flag Status: Flagged
Good afternoon everyone —
Attached you will find a report for the above named bridges and a schematic of the
findings (PDF) — please review both together as the PDF depicts the locations of the
pictures in the report.
In short, the side bank/wall of Mill Race Pond failed due to the recent storm events and
not only did the pond completely drain out, but now Mill Race is flowing through the
work site (green highlighted area on attached plan sheet). As the water table is still
significantly elevated (and because of the amount of drainage coming down both the
Haw River and Mill Race), both rivers are at or have overtopped and are still currently
flooding out the low lying areas (including the work site). It should be noted that just
upstream of our project there is a dam on both the Haw River and Mill Race. I indicated
the current flow locations in blue on the attached PDF.
While we were on site, it was discussed if the "gates" on the Mill Race dam could be
closed. The Glen Raven folks indicated that they had no problem with NCDOT shutting
the gates, however, I think we all were in agreement that would be a large liability on
the Division. Further, there is a significant buildup of trash/sediment/vegetation
immediately in front of the gates so I'm not sure how one would actually be able to
close them without first clearing out the debris.
This then leads to the question of IF the gates are closed to stem the flow of Mill Race
onto the project site, where will all the water go? At this point, it appears that the Mill
Race Dam and the Haw River Dam are the same, connected structure and that possibly,
dirt was laid over top of the stone dam to provide an access way (this would be the 10-
15 feet that separate the two). It would seem very likely that Mill Race would "backup"
until the stream was able to leave its banks and flood the area between the dams and
then flow over the Haw River Dam (and based upon current water levels, it wouldn't
take much for this to occur). There is a question, however, regarding the stability and
safety of the Haw River Dam. I've attached a picture of the area immediately below the
Haw River dam which clearly shows ongoing erosion. Would our actions of closing the
gates on Mill Race possibly increase this erosion if the stream found its way over this
portion of the dam?
This is the reason behind including all of you on this email. There are hydraulics issues
in play here that I and other staff cannot adequately address; I know that Bill and Craig
worked on this one and did the modeling so I've included them for their expertise and
guidance on how best to proceed. There is also the eventual need to rebuild the side of
the pond that washed away; we did discuss the timing of that type of work possibly
being done in conjunction with the final grading on that side of the project when the
temporary bridge structure is removed. This would more than likely necessitate
discussions with Glen Raven folks as that timeframe would be in another year from
now. I also believe that dam safety may need to be involved due to the recent events,
including the washing out and potential rebuilding of Mill Race pond. I believe that the
Haw River Dam is a High Hazard Dam and so the Dam Safety folks probably need to be
consulted regarding closing the gates on Mill Race and sending more water over the
Haw River Dam. At this point, I'm just trying to cover all the bases.
From an erosion control standpoint and environmental permitting standpoint, the site is
currently under water and clearly it's too dangerous to do any assessment of the
damage let alone repair. We will keep the agencies appraised of the situation (they are
also on this email). Ironically, in one spot the silt fence and hardware cloth opening are
still standing; water is flowing over them, but they are still standing!
So, we in the Division are requesting input from the Hydraulics folks on what can and
should be done so that Dane can get back to work and so that we can protect the
existing structures from being washed away. Once the site is no longer under water,
we'll also be able to assess the necessary repairs for sediment and erosion control,
permit limits, etc. We will also need to discuss what, if any, modifications to the existing
permits may need to be required.
Thanks everyone — please feel free to forward this to anyone that I may have left off.
Nikki
Nicole J. Thomson, PWS
Division Environmental Supervisor Assistant
Division Environmental Office
919-754-7806 Mobile
Nithomson2(c�ncdot.qov
PO Box 14996
Greensboro, NC 27415-4996
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