20100642 Ver 1_WRC Comments_20100813

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0 North Carolina Wildlife Resources Commission 0
Gordon Myers, Executive Director
MEMORANDUM
TO: Andrew Williams, Raleigh Regulatory Field Office
U. S. Army Corps of Engineers
FROM: Shari L. Bryant, Piedmont Region Coordinator
Habitat Conservation Program
DATE: 13 August 2010
SUBJECT: Draft Prospectus for Applied Botany Concepts for La Foresta Stream Mitigation Bank,
Guilford County, North Carolina.
Biologists with the North Carolina Wildlife Resources Commission (NCWRC) have reviewed the
subject document and we are familiar with the habitat values of the area. Our comments are provided in
accordance with provisions of the Clean Water Act of 1977 (as amended), Fish and Wildlife Coordination
Act (48 Stat. 401, as amended; 16 U.S.C. 661-667d), and North Carolina General Statutes (G.S. 113-131 et
seq.).
Applied Botany Concepts proposes to establish the La Foresta Stream Mitigation Bank. The site is
currently used for livestock grazing, and approximately 4,500 linear feet of unnamed tributaries to North
Buffalo Creek in the Cape Fear River basin flow through the site. Approximately 50 percent of the main
stream channel is within a transmission line right-of-way maintained by Duke Energy. A combination of
restoration and preservation will be used that includes creating a vegetative buffer, improving dimension,
pattern, and profile of impaired stream sections, and incorporating structural improvements. A conservation
easement will be used to protect the site. The objective is to improve onsite and downstream water quality,
provide flood attenuation, and reverse aquatic and riparian habitat degradation.
The applicant states "Much of the main stream channel is within a Duke Energy transmission line
maintenance easement. It is of the upmost importance that the stream alignment be relocated outside of the
transmission line easement." While we recognize potential benefits to relocating the stream outside of the
transmission line easement, we are concerned that the proposed relocation appears to be upslope of the
existing stream channel. Relocating the stream channel upslope may require removing a significant amount
of soil to re-establish a floodplain at a lower elevation. From the information provided in the draft
prospectus, it is not possible to determine that the benefits of relocating the stream channel in this area
outweigh the risks. Stream enhancement such as fencing out livestock and allowing a scrub/shrub riparian
buffer to develop along that section of the stream within the transmission line right-of-way could provide
significant benefits to the stream.
Mailing Address: Division of Inland Fisheries • 1721 Mail Service Center • Raleigh, NC 27699-1721
Telephone: [phone] • Fax: [phone]
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13 August 2010
Draft Prospectus - La Foresta Stream Mitigation Bank
The applicant states "Applied Botany Concepts must relocate the stream alignment in order to
adequately provide stream mitigation on this site. Without this relocation, the mitigation project is no longer
feasible." We do not feel this is a sufficient reason to relocate a stream channel. Relocation of a stream
channel should be based on identified functional benefits to stream geomorphology, water quality, and
aquatic life on the site and in the downstream watershed.
The applicant states "Due to constraints resulting from existing floodplain morphology and in an
effort to preserve the stream's natural alignment, Applied Botany Concepts will reduce the buffer width on
the west side of the main stream where it adjoins the transmission line easement. It is understood that this
buffer reduction will result in a decrease in mitigation credits." This statement is unclear. The applicant is
proposing to relocate the stream channel which means the stream's natural alignment will not be preserved.
We are concerned about a reduced riparian buffer and long-term channel and bank stability in a stream that
has been relocated upslope of the existing channel. Riparian buffers are important to maintain long-term
bank stability, and are needed to improve aquatic habitat (e.g., woody debris and leaf packs), and to moderate
stream temperatures through shading.
At this time, we have several questions and concerns regarding the proposed mitigation bank. We
are concerned about relocating the stream channel upslope from the existing stream channel and reducing
riparian buffers. We feel more information is needed to determine that the benefits of relocating the stream
outweigh the risks. We need to be assured that the proposed project will result in long-term channel and
bank stability and provide benefits to water quality and aquatic habitat on site as well as downstream. To
complete our review, we request the following information:
• A topographic map showing the contour elevation(s) of the existing stream channel and the
contour elevation(s) for proposed relocated stream channel.
• Please label each tributary (as described in Exhibit 1) on Figure 2, and include whether the
tributary is perennial or intermittent. Based on the Channel Stability Assessment (Exhibit 1), it
appears most of the sediment is coming from one tributary, and not from the main channel.
Identifying the tributaries on a map would be helpful to identify problem areas within the site,
and potential restoration areas.
• Detailed information on the length of the existing stream channel and the proposed length of
relocated stream channel. Also, please include which areas are proposed for restoration or
preservation and how it is anticipated that the stream mitigation units (credits) for this bank will
be determined.
• We have several questions regarding the proposed relocated channel design, these include:
o How the relocated channel will be moved upslope? As indicated, this may require removing
a significant amount of soil to re-establish the floodplain at a lower elevation.
o How wide will the riparian buffers be for the relocated channel, particularly on the west side
adjacent to the transmission line. Please include whether there will be any restrictions on the
types of vegetation (e.g., trees) within the riparian buffer on the west side of the relocated
channel.
o How will plugging and filling the existing channel be done?
o Is the proposed design sufficient to handle build-out conditions in the watershed? It is
indicated this is in an urbanizing watershed.
o We recognize that Figure 2 is a simplistic graphic showing the existing and relocated stream
channels. However, the stream channel design for the relocated channel is relatively
uniform and resembles a sine wave. Will the final design have more variation in the pattern?
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13 August 2010
Draft Prospectus - La Foresta Stream Mitigation Bank
Thank you for the opportunity to review and comment on this draft prospectus. If we can be of
further assistance, please contact our office at [phone].
cc: Howard Hall, USFWS
Rebecca Fox, USEPA
Ian McMillan, DWQ