20120040 Ver 1_Mitigation Site Review_20141212

Wainwright, David
From: Wainwright, David
Sent: Friday, December 12, 2014 10:06 AM
To: Sarah.E.Hair @usace.army.mil
Cc: King, Art C ; Baker, Virginia (virginia.baker @ncdenr.gov)
Subject: B-3680 Sediment Discharge and Mitigation Site
Attachments: 14.pdf, Sediment discharge to stream and mitigation site.pdf
Liz,
I visited the B-3680 last Monday, December 8, in response to the ICA that was issued the prior week. I have attached
some pictures.There were several things to note:
• There were about three places where sediment had been washed from under the coir fiber matting an into the
stream. Relatively speaking,these were minor discharges. Sediment was of heavy sand. A small plume of
sediment we released when I put my hand in it, but there was no apparent flow that day, and the plume,which
was of a much finer material than the actual discharge, dissipated/settled within a few minutes. I estimated this
to be less than 10 five gallon buckets worth and was the largest of the releases. I asked them to do what they
could to stabilize the bank and keep additional sediment releases from occurring.
• There was a waddle on the upper end that drained a low area that had some sediment from under the coir fiber
mat to be released. I estimated this to be less than 5 five gallon buckets.They were going to pull the mat back,
repair the erosion, and relay the mat taking it probably 15-20 back behind the waddle into the mitigation site.
• Because of the fairly small amount of sediment released and the nature of the environment, I decided that it
would be best to not mess with the discharged sediment. I think it would be difficult to remove it without doing
damage to the stream and/or mitigation site. One of those "leave well enough alone" situations. I asked when
the banks would be planted and was told it would be done with the mitigation site planting,which is expected to
be within the next few weeks. I told them to keep an eye on the banks to make sure that no additional issues
that could result in discharge arise.
• The areas around the trees that were left had a little bit of slope due to the elevation differences.They agreed
to lay some coir fiber matting along these slopes to help prevent sloughing and erosion until the spring when the
vegetation can become well established.
• The area that was excavated in the wet looked very good and you could not tell they had done it. It was along
the wing wall bank and had been stabilized with riprap as is typical. I didn't see anything that needed to be done
in this area.
• The mitigation site is getting close to being planted.There was water standing in many areas,which is good.
They seemed to have tied into the existing wetlands pretty good. I was not as pleased with the tie into the
stream banks, but we'll see.
• One of the questions posed was about the disking of the site.They kept asking me, and I kept telling that should
be up to DOT. The plans call for it, but none of them onsite thought it was necessary.Jason Elliot was going to be
out there the following day to review the site; ask him.
I think this is all. Overall it isn't looking too bad. Call me if you want to discuss anything further.
David Wainwright
NCDENR,Division of Water Resources
1617 Mail Service Center,Raleigh,North Carolina 27699-1617
Phone: [phone] Fax: [phone]
David.Wainwright @ncdenr.gov
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