20201297 Ver 1_RE_ _External_ West Duncan Street Culvert - Lillington NC_20201014 (2)

Carpenter,Kristi
From:Sean Clark <[e-mail]>
Sent:Monday, November 02, 2020 4:47 PM
To:Steenhuis, Joanne; David Arnold
Cc:Greer, Emily C SAW
Subject:RE: \[External\] West Duncan Street Culvert - Lillington NC
Attachments:IMG_1418 View looking downstream at existing culvert inlet.JPG; IMG_1415 View
looking upstream from the road.JPG
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Emily,
I’ve attached a couple of photos of the area upstream of the project area. I will send a couple of the downstream area as
well in a separate email. If you would please review the site plan with the associated photos and let us know if a request
for written approval is needed or if the replacement can proceed as non-reporting.

Thanks

Sean Clark
Sage Ecological Services, Inc.
Cell: 919.559.1537
[e-mail]

From: Steenhuis, Joanne <[e-mail]>
Sent: Friday, October 30, 2020 1:20 PM
To: David Arnold <[e-mail]>
Cc: Greer, Emily C SAW <[e-mail]>; Sean Clark <[e-mail]>
Subject: RE: \[External\] West Duncan Street Culvert - Lillington NC

Looks good!

From: David Arnold <[e-mail]>
Sent: Friday, October 30, 2020 1:12 PM
To: Steenhuis, Joanne <[e-mail]>
Cc: Greer, Emily C SAW <[e-mail]>; Sean Clark <[e-mail]>
Subject: RE: \[External\] West Duncan Street Culvert - Lillington NC

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Joanne,

Can you please let me know if this works? I added the floodplain bench, changed sills to concrete, and added a detail to
show the stream channel w/baffles.

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I will work with Sage Environmental regarding the silt bag, coffer dam, etc. I just want to be sure I have all the key final
elements so I can start getting some bids for this replacement.

Thanks,

David Arnold, PE

Mobile [phone]
www.thenauco.com

From: Steenhuis, Joanne <[e-mail]>
Sent: Friday, October 30, 2020 12:22 PM
To: David Arnold <[e-mail]>
Cc: Greer, Emily C SAW <[e-mail]>
Subject: RE: \[External\] West Duncan Street Culvert - Lillington NC

From: David Arnold <[e-mail]>
Sent: Friday, October 30, 2020 12:20 PM
To: Steenhuis, Joanne <[e-mail]>
Cc: Greer, Emily C SAW <[e-mail]>
Subject: RE: \[External\] West Duncan Street Culvert - Lillington NC

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Did you find a detail for the baffles? Trying to determine how these would stay stable inside the pipe. A weir on each
end of the pipe (4’ wide x 1’ tall) seems like it may be a better long term solution (without seeing a good detail of how
the baffles work).

Thanks,

David Arnold, PE

Mobile [phone]
www.thenauco.com

From: Steenhuis, Joanne <[e-mail]>
Sent: Friday, October 30, 2020 11:20 AM
To: David Arnold <[e-mail]>
Cc: Greer, Emily C SAW <[e-mail]>
Subject: RE: \[External\] West Duncan Street Culvert - Lillington NC

David,
Have you sent new drawings with the changes and I missed them? They need to show baffles in the pipe to keep the
stream at the normal width ( which I think is approximately 4 feet), sills in the pipe (not sheet pile) on both ends of the
storm overflow pipe and the flood plain bench at the inlet end of the storm overflow pipe.

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The location of the coffer dam on the up stream side and for the calculating the impacts to the stream for the
application, the area from the coffer dam to the pipe will be considered temporary impacts.

Please, detail how the remaining water within the stream will be handled (silt bag, pumping over high ground, etc.) It
will most likely be turbid and cannot be put back into the stream until it is less than 50 NTU or less.
Just a reminder that an application cannot be submitted until your 30 days is up. Have you discussed this with Emily
Greer to see if it fits under a NW 3 reporting or non-reporting? If it does, you can use the shorter version of our
application to submit it to us and the USACE.

From: David Arnold <[e-mail]>
Sent: Friday, October 30, 2020 9:34 AM
To: Steenhuis, Joanne <[e-mail]>
Subject: RE: \[External\] West Duncan Street Culvert - Lillington NC

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Joanne,

Have you had a chance to review these plans yet? We are trying to get this out to bid so we can get this road back open.

Thanks,

David Arnold, PE

Mobile [phone]
www.thenauco.com

From: Steenhuis, Joanne <[e-mail]>
Sent: Monday, October 26, 2020 11:41 AM
To: David Arnold <[e-mail]>
Cc: Sean Clark <[e-mail]>; [e-mail]; Joseph Jeffries <[e-mail]>;
Alicia Gregory <[e-mail]>
Subject: RE: \[External\] West Duncan Street Culvert - Lillington NC

The pipe sizes are fine. You will want to place baffles in your main pipe, to maintain the existing stream width. In the
overflow pipe, the sills are usually placed on both sides (ends)of the pipe to allow the sediment to remain in the
pipe. Concrete is the preferred type of sill.

I am looking for a baffle detail, which I will send when I get it.

From: David Arnold <[e-mail]>
Sent: Monday, October 26, 2020 10:43 AM
To: Steenhuis, Joanne <[e-mail]>
Cc: Sean Clark <[e-mail]>; [e-mail]; Joseph Jeffries <[e-mail]>;
Alicia Gregory <[e-mail]>
Subject: RE: \[External\] West Duncan Street Culvert - Lillington NC

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Joanne,

Thanks for the detail and feedback. I can update the sheet pile sill to a concrete one if that helps. We can also pipe rip
rap in front of it to create the ledge.

For the stream width, I unfortunately need the 96” pipe. We are draining approximately 2.5 square miles to this culvert
and a 48” in culvert (to match old stream) just won’t cut it to handle the flows. The existing pipe is a 72” pipe and it is
severely undersized to handle the flows coming to it, thus the road blowout. I’d also point out that the existing stream
downstream of the culvert is much wider than 4’ at the outlet area. That’s the large plunge pool we saw. It eventually
channelizes back to the smaller ~4’ streambed. Based on current topography, even if we put in a smaller pipe the runoff
would spread out in the plunge pool area before reconcentrating downstream. Please let me know if maintaining these
pipe sizes are acceptable.

Thanks,

David Arnold, PE

Mobile [phone]
www.thenauco.com

From: Steenhuis, Joanne <[e-mail]>
Sent: Thursday, October 22, 2020 10:26 PM
To: David Arnold <[e-mail]>
Subject: RE: \[External\] West Duncan Street Culvert - Lillington NC

David,
This is the best drawing I have that covers the concerns I had; the sills for the floodplain pipes and the floodplain bench I
told you about in front of the floodplain pipe. The drawing also shows the flood plain bench being constructed from soil,
but it can also be constructed from rip rap and over time sediment will fill in the gaps in the riprap.

A sheet pile sill may not meet out requirements. I will need to ask around.

I will need to reiterate that you are not allowed to widen the natural stream width. If the pipe is wider than the stream
you may be required to install baffles in the pipe to keep the stream at a similar width.

I will see if I can find any better drawings and I will also review the drawings you have sent me.

Thanks!
Joanne

From: David Arnold <[e-mail]>
Sent: Thursday, October 22, 2020 11:47 AM
To: Steenhuis, Joanne <[e-mail]>
Cc: Sean Clark <[e-mail]>; [e-mail]; Joseph Jeffries <[e-mail]>;
Alicia Gregory <[e-mail]>
Subject: \[External\] West Duncan Street Culvert - Lillington NC

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Joanne,

Thank you for meeting us onsite yesterday to look at the failed culvert in Lillington, NC. I’ve updated the plans per our
conversations. I’ve added the limits of existing impact, shown rip rap, added profile, and have proposed a 2’ sheet pile
in front of the second culvert so that normal flow only goes through one pipe.

Can you please let me know any additional feedback you have?

Thanks!

David Arnold, PE

Mobile [phone]
www.thenauco.com

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