20170239 Ver 1_U-3109 pond_erosion control basin conversion_20220408

Strickland, Bev
From: Conchilla, Ryan
Sent: Friday, April 8, 2022 12:41 PM
To: Parker, Jerry A; '[e-mail]'
Cc: Wanucha, Dave; Lipscomb, Brian S; Mullins, Ryan M; McDaniel, Andrew H.
Subject: U-3109 pond/erosion control basin conversion
Attachments: U-3109A Site 12 (Plan Sheet).pdf; U-3109A Site 12.pdf
Jerry,
Thanks for the hydraulic update. If purchasing the permanent right of way for this area is not an option, we concur with
Option #2 selected below.
To proceed with Option #2, please provide an updated site plan (sheet 12) with the estimated length/width/depth, rip -
rap Class and cy. for the two proposed ditch lines. It should be noted that site restoration and re -vegetation of this area
should adhere to the Standard Permit conditions with a recommendation for using a wetland seed mix in the adjacent
saturated areas.
Due to the urgency expressed by DOT to begin repairs and stabilization efforts on -site, immediate mobilization is
authorized. However, the items listed above should be provided for review at the earliest convenience.
If I can provide further assistance, let me know.
Have a great afternoon -
Ryan Conchilla, PWS
Environmental Specialist II
401 and Buffer Transportation Permitting Branch (DOT Divisions 7+8)
Division of Water Resources, NC Department of Environmental Quality
[e-mail]
From: Parker, Jerry A <[e-mail]>
Sent: Friday, April 8, 2022 7:47 AM
To: Conchilla, Ryan <[e-mail]>; Wanucha, Dave <[e-mail]>
Cc: [e-mail]
Subject: FW: U-3109 pond/erosion control basin conversion
Ryan and Dave,
We met with the hydraulic engineers on Thursday and I am forwarding you their response. We can talk about this later
after you have had a chance to digest.
Jerry
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From: Lipscomb, Brian S <[e-mail]>
Sent: Thursday, April 7, 2022 4:15 PM
To: Parker, Jerry A <[e-mail]>
Cc: [e-mail]; McDaniel, Andrew H. <[e-mail]>; Mullins, Ryan M <[e-mail]>
Subject: U-3109 pond/erosion control basin conversion
Jerry and Della,
Thanks for meeting with Ryan and I on -site this morning to discuss options for post -construction conversion of the
existing erosion control basin/former pond.
A recap of the options we discussed:
Option 1 (Grade flat as permitted)
• With the discovery of the spring at the toe of the fill slope producing a constant flow the area would stay
saturated and likely restrict ability to establish a good turf grass buffer. With the flows that were evident out of
the two pipes it is believed this would end up being an erosion issue and cut new channels with excessive
sediment loss downstream.
Option 2 (Grade in two rock lined channels from the pipe outlets converging into one)
• This would provide for a stable conveyance of both the constant flow from the spring as well as storm flows
from the two pipes. This option provides for the most likely to opportunity for establishment of vegetation
outside of the ditch area and reducing the chance of erosion and sediment loss.
Option 3 (Conversion to a post -construction stormwater control measure (ie. Wetland)
• Generally the site would lend well to creating a wetland with the constant baseflow from the spring. However,
based on the signs of significant flow out of the pipes there is concern about being able to provide non -erosive
velocity into the wetland thus erosion would be a concern. In addition and at this point likely one of the most
important aspects is the lack of access post -construction. The site is not accessible from the highway as it is
down a high, steep fill slope behind guardrail. The site is within a temporary construction easement, thus DOT
doesn't own the property and it will revert back to the property owner upon completion and access from
Edgewood Church Road will no longer exist.
Based on our observations and the current circumstances it is my recommendation to go with Option 2 and regrade the
area and provide two converging rock lined conveyances. This will provide the most stable option and reduce likelihood
of future erosion and sediment loss to the downstream waterbody. Lack of property ownership or permanent easement
and lack of access would restrict ability to inspect and maintain anything else at this location long-term.
Please let me know if you would like to discuss further.
Thanks,
Brian
Brian S. Lipscomb, PE
Engineer - Advanced
North Carolina Department of Transportation
Hydraulics Unit, Highway Stormwater Program
919 707 6700 (office -main)
919 707 6735 (office -direct)
919 745 7553 (mobile)
blipscomb©ncdot.gov
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