20050785 All Versions_Mitigation Information_20060815

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STATE OF NORTH CAROLINA
DEPARTMENT OF TRANSPORTATION
MICHAEL F. EASLEY LYNDO TIPPETT
GOVERNOR SECRETARY
August 15, 2006
Brian Wrenn
NC department of Water Quality
2321 Crabtree Blvd.
Raleigh, NC 27604
William Wescott
US Army Corps of Engineering
Post Office Box 1000
Washington, NC 27889-1000
Subject: On-site Mitigation for Washington Bypass in Beaufort County- Lilly Property Site
Dear Sirs:
Attached is the evaluation from Earth Tech of North Carolina, Inc. for the Lilly property as a
potential wetlands creation site. The site was found to be unfeasible with a high risk for failure.
The Department of Transportation (PDEA) agrees with this evaluation.
If you have any comments or questions, please notify me by September 7, 2006. This will allow
time for the concerns to be investigated and addressed in the Merger 01 4C meeting. The
meeting is scheduled for September 21, 2006 at 1:00 pm in the Transportation Board Room in
Raleigh.
Thank you for your willingness to visit the site and to provide your professional expertise.
Sincerely,
Rodger Rochelle
State Alternative Delivery Engineer
RDR/adg
Attachment
cc: Chris Militscher; US Environmental Protection Agency (w/ attachment)
Travis Wilson; NC Wildlife Resources Commission (w/ attachment)
Gary Jordan; US Fish and Wildlife Service (w/ attachment)
Steve Sollod; Division of Coastal Management (w/ attachment)
John Hennessy, NC Department of Water Quality (w/ attachment)
MAILING ADDRESS: TELEPHONE: [phone] LOCATION:
NC DEPARTMENT OF TRANSPORTATION FAX: [phone] CENTURY CENTER COMPLEX
PROJECT SERVICES UNIT ENTRANCE B-2
1591 MAIL SERVICE CENTER wEBSITE: WWW.DOH.DOT.STATE.NC.US 1020 BIRCH RIDGE DRIVE
RALEIGH NC 27699-1591 RALEIGH NC
@ Earth Tech
A tgCO International Ltd. Company
August 14, 2006
Mr. Roger Rochelle.
North Carolina Department of Transportation
Mail Service Center 1591
Raleigh N C 27699-1591
Re: NCDOT TIP R-2510B
US 17 Washington Bypass
Lilly Property Mitigation Site
Dear Mr. Rochelle,
701 Corporate Center Drive P 919.854.6200
Suite 475 F 919.854.6259
Raleigh, NC 27607 earthtech.com
Earth Tech is evaluating and developing compensatory mitigation plans for stream and wetland mitigation
sites associated with the US 17 bypass of Washington, North Carolina. One site know as the Lilly
Property was under consideration for both stream and wetland mitigation. Upon further evaluation of the
Lilly Property, Earth Tech has determined that stream and wetland mitigation at this property is not
practical or feasible.
Mitigation at the Lilly Property would be wetland creation and consist of grading and removing a large
agricultural field between two unnamed tributaries to Cherry Run Creek. The site was first brought to the
attention of Earth Tech when S.T. Wooten was evaluating the property as a potential borrow site. Test pits
performed by S.T. Wooten at the western portion of the field indicated that the soil profile in,this area is as
follows:
0 to 1 ft - topsoil
1 to 4 ft - sandy clay
4 to 8 ft - sand
Below 8 ft - clay
Of the above material only the 4-foot sand layer at 4 to 8 feet would provide borrow suitable for road
construction. The top 4 feet is not suitable nor is the clay which occurs at 8 feet. Additionally, the clay is
a highly cohesive fine clay "gumbo" that is extremely difficult to work. It was estimated that to create a
14 acre wetland about 200,000 cubic yards of material would need to be removed. Of this only about
50,000 to 70,000 cubic yards would be suitable for borrow. The remaining material would need to be
distributed across the upland areas of the site.
The elevation of the top of the field is 10 to 13 feet. With a target elevation of 1 to 1.5 feet, to implement
the wetland mitigation it would be necessary to remove about 2 to 3 feet of clay to allow for backfilling
with topsoil. In discussing possible construction options with S.T. Wooten it was determined that working
with this clay layer (excavating, grading, etc.) would be very difficult if not impossible to perform due to
the properties of the clay. The clay layer is at or below groundwater. When wet it would not be possible
to drive construction equipment directly on the clay layer, and it would be necessary to leave a layer of
sand to drive upon reducing the usable borrow even further. Due to the nature of working with this clay
layer it would be extremely difficult to accurately grade the site and reach/match a target elevation
necessary for the mitigation to be successful. Additionally, over grading and backfilling with topsoil
@) EarthTech
A'tgCO International Ltd. Company
August 14, 2006
Mr. Roger Rochelle
Page 2 of 2
would also not be practicable. Without being able to backfill with topsoil the chance of successfully
establishing vegetation is very low.
Creation of wetlands from an upland area always has an element of risk in that it will not be successful.
Because of this, credit ratios for wetland creation are less than that obtained for restoration. Therefore,
mitigation at this site will yield less credit for the amount of effort required.
Earth Tech visited the site on July 21, 2006 to conduct additional studies for stream restoration design on
the unnamed tributary to Cherry Run. The stream, which was thought to be perennial, was dry. No flow
was detected for a considerable distance down through the stream/wetland system. Rainfall for the area
has been within a normal range for the area so this is not an atypical situation for this stream system.
Therefore, it was determined that the stream system is an intermittent system and not a perennial system as
originally thought based on biological indicators observed during the winter and spring. NCDOT
currently does not obtain credit for restoration of intermittent stream systems.
The above information was discussed with Morgan Weatherford (NCDOT Natural Environment Unit)
who concurred that both the stream and wetland mitigation options proposed for the Lilly Property did not
appear to be feasible.
Given the difficulty of implementing the mitigation, risk of the mitigation being unsuccessful, lower credit
ratios, intermittent nature of the stream, and high cost of implementation, wetland/stream mitigation on
this site is not feasible or practicable. Therefore, Earth Tech recommends that this site not be pursued any
further as a stream or wetland mitigation site.
Sincerely,
Earth Tech of i Carolina, Inc.
Ron Jo on
Senior iologist
cc: Paul Newman, Flatiron
Tom Shearin, PE .
060815 Rochelle-Johnson-Lilly Site_Letter2[1]1.doc