19970722 Ver 1_More Info Letter_19980824

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State of North Carolina
Department of Environment
and Natural Resources
Division of Water Quality
James B. Hunt, Jr., Governor
Wayne McDevitt, Secretary
A. Preston Howard, Jr., P.E., Director
1 ?•
NCDENR
NORTH CAROLINA DEPARTMENT OF
ENVIRONMENT AND NATURAL RESOURCES
April 24, 1998
Andrea M. Spangler
Environmental and Special Projects Manager
Piedmont Triad Regional Water Authority
Wilmington Building, Suite 207
2216 West Meadowview Road
Greensboro, NC 27407-3480
Dr. Gerald McCrain
EcoScience Corporation
612 Wade Avenue
Raleigh, NC 27604
Re: Randleman Lake Compensatory Mitigation Proposal
Dear Ms. Spangler and Dr. McCrain:
John Dorney and I have reviewed the latest proposal submitted by EcoScience for
the wetland mitigation for the Randleman Lake project. As we have stated in previous
communications the four sites proposed (Richland Creek, Reddick Creek, Hickory Creek,
and Muddy Creek) have potential for wetland restoration and creation. As opposed to
the last proposal, which involved extensive excavation and stream relocation, EcoScience
has proposed utilizing instream weirs to raise the water levels and bring the hydrology on
the adjacent floodplain up to jurisdictional levels with minimal earthwork.
The Division feels that this is a more environmentally and economically sound
approach to wetland creation and restoration, but from the data that has been provided
the actual acreages of wetlands to be created or restored have dropped significantly. For
the four sites proposed by EcoScience a total of 81 acres of wetlands were proposed.
However, subtracting the existing wetland acreages identified in the August 1997
proposal leaves 60.4 acres of wetland creation or restoration. That is only half of the 120
acres needed to meet the 1:1 wetland mitigation criteria. The Division agrees with the
principal of looking at a mitigation site holistically with levee habitat and upland buffers,
but the minimum 1:1 ratio must be met.
Environmental Sciences Branch 4401 Reedy Creek Road Raleigh, North Carolina 27607
Telephone [phone] FAX # [phone]
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We feel that additional sites can be found within the proposed lake watershed. A
quick review of the USGS Quad Sheets can reveal a number of potential floodplain
mitigation sites. In a letter from Mr. Ed Powell on September 4, 1997, Mr. Powell
concurred that the Authority needed to find an additional 10 to 15 acres of wetland
mitigation to meet the 1:1 mitigation ratio at that time. It appears that the Authority has
chosen not to look for the additional mitigation sites that were needed then and are
definitely needed now.
More specific comments on the Richland Creek, Reddick Creek, Hickory Creek,
and Muddy Creek sites are identified below. For all the sites there is concern about the
stormwater energy that occurs in the streams and the need to look at try to model the
surface water flows within the watersheds. Along with these flows there is significant
sediment transport and deposition that will need to be dealt with at the instream weirs.
Build up of sediment behind the weirs could lead to the stream cutting around the weirs
and eroding the restored wetland area. Downstream effects and the interruption of
sediment transport may be a concern at the Muddy Creek site. These issues should be
addressed in the design of the weir structures.
It would appear from elevations shown on the Richland Creek site that you could
extend zones 2 or 3 further up several of the lateral drainages where you currently show
upland buffer. This may gain several more acre of mitigation at this site. Weir D may
be under tremendous pressure during stormwater flows. At the Hickory Creek site we
are concerned about the amount of successful wetland creation within the narrow stream
valley. As expressed at our meeting, the Reddick Creek site poses additional challenges
with the lack of hydric soils and steepness of the stream valley. The maintenance and
seasonal adjustments of the weir heights are of concern. In order to maximize the
wetland mitigation potential at this site, you may want to consider some excavation of
the wider stream valley below dam #1.
Overall, we believe that the four sites discussed above should work as wetland
mitigation sites. However, specific plans need to be put together with the appropriate
target wetland (bottomland hardwood forest) in mind. These plans will need to address
the concerns expressed above as well as the maintenance seasonal adjustment of the
weirs. Should you have any questions or wish to discuss additional mitigation sites
please contact Pete Colwell or myself at 919-733-1786.
S' er ,
Jo . Dorney
We ands / 401 Gro
cc: Ed Powell, DMP
Ron Linville, DWQ Winston-Salem Regional Office
David Franklin, US Army Corps of Engineers
Pete Colwell, DWQ Central Office