20070747 Ver 1_Other Agency Comments_20080820

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UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
REGION 4
T ATLANTA FEDERAL CENTER
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r~~ pRUt~ ATLANTA, GEORGIA 30303-8960
AUG 1 8 20103 rc
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Mr. David Lekson
U.S. Army Corps of Engineers
Post Office Box 1000
Washington, NC 27889 - 1000

Subject: Flat Swamp Mitigation Bank; Phase II Draft Preliminary Mitigation Plan
ORM ID SAW-1999-11312.

Dear Mr. Lekson:

This letter is in response to your request for comments on the preliminary mitigation plan
for Phase II of the Flat Swamp Mitigation Bank, in Craven County, North Carolina. The U.S.
Environmental Protection Agency (EPA), Region 4 Wetland Regulatory Section has reviewed
the Phase II Preliminary Mitigation Plan. We note that EPA signed the Mitigation Banking
Instrument (MBI) for Phase I in May 2000 and signed an amendment to the MBI on August 28,
2002. Phase I involved the restoration of 318.34 acres of wetlands, and enhancement of 47
acres. We understand that construction has not yet been initiated at the site for Phase I.
The Phase II mitigation plan does not indicate the specific changes that may be needed to
the Phase I wetland mitigation plans. Paragraph 27 of the amended MBI states that an area of
20.66 acres (9,000 feet long by 100 feet wide) is not included in the Phase I calculations and is
reserved for Phase II. However, it appears that Phase II may need to be constructed before Phase
I is initiated, and it may not be possible to conduct the stream restoration portion of the project
without significant changes to the plans approved for Phase 1. In this proposal for Phase II, the
sponsor proposes 15,895 linear feet of headwater stream, almost 7,000 linear feet longer than
predicted in the Phase I mitigation plans. We recommend that the sponsor discuss the changes to
Phase I more specifically in this document. Since no work has been done on the site, it would be
preferable for the sponsor to revise the mitigation plans for Phase I at this time, and to discuss
the overall project (Phases I and II together) in one cohesive document.

If the MBI for the Flat Swamp Mitigation Bank is going to be amended, then the
requirements of the April 10, 2008, Mitigation Rule must be followed (33 CFR Parts 325 and
332; 40 CFR Part 230). There may be advantages to amending the MBI. For example, a revised
credit release schedule has been provided by the NC Interagency Review Team for both wetland
and stream mitigation bank credits. However, at this time, it is unclear whether an amendment to
the MBI is necessary.

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On Page 6, the plan refers to the dichotomous wetland key from the NC Wetland
Assessment Method (NCWAM), which is now being used to categorize wetland types for both
impact and mitigation sites. I recommend that the bank sponsor use the NCWAM wetland type
for all descriptions of the project and revise the mitigation plans and MBI to reflect the new
wetland type names. For example, the Zone Description in Table 3 of the Phase II plan should
be revised to indicate the NCWAM wetland type. Other descriptions (such as HGM type) do not
need to be included in the plans, since all agencies in North Carolina now recognize the
NCWAM wetland types.

In the 2002 amendment to the MBI, the area for Phase II is described as 100 feet wide.
However, EPA recommends that the width of the stream corridor be determined by measuring 50
feet from the outer belt width or the outermost braid on either side of the stream channel. This
may result in a greater than 100-foot wide stream buffer corridor, but will avoid future credit
issues. Specifically, if a buffer is less than 50-feet wide on either side of the stream, there is the
potential that no credit will be given (as this project is in the Neuse buffer rules area, and the
rules require a 50-foot buffer on both sides). We acknowledge that because it appears that all of
the stream reaches will be located completely within the Flat Swamp project boundaries, the
buffer widths may not be a significant issue (if areas beyond the designated stream corridor will
be restored or enhanced wetland). Also, we recognize that some or all of the stream reaches may
not have much pattern due to the design, and a 100-foot wide corridor may suffice. However,
the plan should clearly state that a minimum of 50-foot buffers will be provided on both sides of
the restored stream channel.

It appears from Page 11 of the plan that all stream reaches are proposed for credit for the
valley length (per the Coastal Stream Guidance). For any reaches where stream credit is being
sought (under the 2003 Stream Mitigation Guidelines), monitoring should include macrobenthos
(dip net sweeps), and success criteria should include a demonstration that species within the
reaches are typical of those found in flowing streams. If a demonstration of flow can be made,
then the reaches may receive 1:1 stream credit for the entire sinuous length. If a demonstration
of flow cannot be made, the reaches may qualify for credit for the valley length (per the Coastal
Stream Guidance).

On Page 13, the plan proposes to create an "open water bottomland swamp community at
the confluence of the northernmost swales and north to south ditch." EPA recommends that the
sponsor attempt to limit the amount (and particularly the depth) of open water on the site. The
sponsor should be aware that if trees or other significant wetland vegetation do not colonize this
area, the likelihood of receiving mitigation credit for open water areas is slim.

On Page 14, the plan refers to the use of appropriate herbicides to promote establishment
and protection of desired native species vegetation. EPA is concerned about the use of
herbicides on wetlands and mitigation sites. We recommend that physical removal of invasive or
exotic vegetation be used whenever possible, rather than herbicides. In extreme cases, herbicides
may be used, but should be applied carefully following label requirements and directly to the
targeted plant, to avoid contamination of soil and groundwater. Under no circumstances should
herbicides be applied broadly across the site.

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The mitigation plan should include a separate section discussing success criteria for
stream hydrology, overbank flooding, and riparian buffer tree survival. All success criteria
should be quantitative. Success criteria for the stream should include quantitative evidence of
the appropriate frequency and extent of overbank flooding in the adjacent floodplain.

Future mitigation plans should include detailed design drawings of all work to be
conducted, and locations of proposed monitoring plots, gauges, cross-sections, and photo
stations.

Thank you for the opportunity to comment on this project. If you have questions or
comments, please call or email Kathy Matthews, of my staff, at [phone] or
[e-mail].

Sincerely,

Thomas C. Welborn
Chief
Wetlands, Coastal and Nonpoint Source Branch

cc: Ron Sechler, NOAA
Howard, Hall, USFWS
Maria Dunn, NCWRC
Eric Kulz, NCDWQ
Guy Stefanski, NCDCM

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