20231166 Ver 1_More Info Received_20231201

Chandler, Rebecca D
From: Amy Black <[e-mail]>
Sent: Friday, December 1, 2023 12:50 PM
To: Chandler, Rebecca D
Subject: [External] RE: Parkdale Culvert Replacement- additional information needed
Attachments: Parkdale Downstream X-Sections.pdf, IMG_9027.JPG
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Hi Rebecca,
I asked our CAD team to provide a couple of cross sections of the downstream channel — one just downstream of the
culvert within the LOD and one a little further down beyond our LOD. The sheet is attached for your review. I also
attached a phot of the downstream discharge so you can see what the existing condition is.
It's not easy to see in the photo, but a good bit of that discharge "pool" is rock. We had a boring drilled in the shoulder
of the road that showed no rock to elevations below the proposed pipe, but we are still concerned that the contractor
will hit rock. If so, they will only excavate through rock if it is needed for the pipe trench. We will not excavate rock in
the stream channel. We will just adjust grading to compensate. You can see from the cross sections that the stream
bank is practically vertical within the construction zone. If we don't hit rock, we want to grade it back a bit to allow
some vegetation for stabilization. If they do encounter rock, we will just grade back starting from the elevation of the
rock.
Beyond our disturbance, the stream bottom is greater than 5 feet wide and the top bank width is greater than 10
feet. The distance from outside pipe to outside pipe for the double culvert is less than 7 feet. It didn't seem to us that
splitting the flow would have a negative impact on the downstream channel.
Please let me know if you would like more information. I would be happy to schedule a Teams call so we could look at
the drawings and photos together if that would help. I am available anytime after 9AM on Monday and anytime on
Wednesday or Thursday of next week. Let me know if you would like to schedule a call.
Thanks
f J
Engineering
Amy Black PE
Project Manager/Water Resources Engineer
o [phone]
c [phone]
e [e-mail]
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From: Chandler, Rebecca D <[e-mail]>
Sent: Friday, November 17, 2023 12:05 PM
To: Amy Black <[e-mail]>
Cc: Lawrence, Jennifer L CIV USARMY CESAW (USA) <[e-mail]>
Subject: Parkdale Culvert Replacement- additional information needed

EXTERNAL MESSAGE — TREAT LINKS/FILES WITH CARE
Hi Amy,
I've completed my review of the Parkdale Culvert Replacement Project and require additional information before
issuing. Please respond within 30 days, and note that the project will be placed on hold until a response to this request is
received.
1. 1 understand that the replacement is due to a current undersized culvert. DWR is concerned that spreading
average flow between two 30-in culverts may result in over widening of the channel, and therefore reduction in
function of the stream. Please respond as to the necessity of both culverts to be installed at the same elevation.
Typically, we see flow isolated to a primary culvert, and the second culvert used as overflow for large flows and
storm events.
2. The stream width is listed at 10-ft, could you please provide the width of the thalweg for purposes of assessing if
one 30-in culvert may be enough for normal flows.
Thank you,
Rebecca Chandler
Environmental Program Consultant
Division of Water Resources
North Carolina Department of Environmental Quality
Winston-Salem Regional Office
450 West Hanes Mill Road, Suite 300
Winston-Salem, NC 27105-7401
336-776-9705 office
336-354-2284 cell
336-776-9797 fax
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