20031035 Ver 1_Mitigation Information_20090102

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2� ,J UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
REGION 4
ATLANTA FEDERAL CENTER
Z�F ,02 61 FORSYTH STREET
tilg4 PROZEG� ATLANTA, GEORGIA 30303 -8960
December 22, 2008
Mr. William Wescott
Washington Regulatory Field Office
U.S. Army Corps of Engineers
P.O. Box 1000
Washington, North Carolina 27889 -1000
J AN � 20015
DS AND STQRt'�A RBR��
Subject: Neu -Con Mitigation Bank: 2008 Monitoring Reports for Nahunta and Marston
Sites
Dear Mr. Wescott:
This letter is in response to your December 15, 2008 letter, requesting review and
comment on the monitoring reports for the following Neu -Con Mitigation Bank sites: Marston
and Nahunta. The U.S. Environmental Protection Agency (EPA), Region 4, Wetland and Marine
Regulatory Section reviewed the monitoring reports and we have the following comments for
your consideration.
Marston Site: The project sponsor requests permission to discontinue monitoring of this site.
The site has met the vegetative and hydrologic success criteria for Years one through five. EPA
agrees that the sponsor may discontinue monitoring this site, and that all remaining credits be
released.
Nahunta Swamp sites: These five sites are in the fourth year of monitoring. The hydroperiod of
most of the wells are improved'over last year. This year, 17 of the 25 gauges on the mitigation
sites met the success criteria established in the mitigation plan (greater than 12.5 percent of the
growing season), compared to only three last year. Four of the 25 gauges did not meet the
jurisdictional criterion for wetland hydroperiod (greater than five percent of the growing season)
while another four met the five percent wetland jurisdictional criterion, but not the success
criterion. Most of the sites were also closer in hydroperiod to the reference wells this year. The
vegetative criteria were met, and most planted species appear to be doing well on all of the tracts.
We continue to be concerned that modeling during the design phase indicated that the
restored hydroperiod would be approximately seven percent across the restored wetland site. It
is unclear why the success criterion for hydroperiod is set at 12.5 percent, if the modeling
indicated a typical hydroperiod of seven percent, although we note that many of the wells did
meet the criteria this year. It is uncertain whether most of the wells will meet the 12.5 percent
criteria for the majority of the five -year monitoring period.
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'We are also concerned with the four wells that did not demonstrate a hydroperiod greater than
five percent of the growing season. Page 22 of the monitoring report states that Gonder Tract
gauges AW 1 and AW5 may be located within highly conductive soil layers. These particular
Gonder Tract wells have not met the success criteria since construction, and the same statement
aboutFp'otential conductive, soils has been made in monitoring reports for several years. Various
Tapp' Tract wells have also Mailed to meet the success criteria during most monitoring years. We
note that at close -out, any acreage which is determined not t6 be jurisdictional wetlands (non -
jurisdictional soils or non jurisdictional hydroperiod) should not be given wetland credit. If the
sponsor- wishes to propose adaptive management measures to determine the source of the
problem, EPA recommends that they do so as soon as possible.
Thank you for the opportunity to comment on this project. Please contact Kathy
Matthews at 919 - 541- 3062,or mathews.kathy @epa.gov with any questions or comments.
Sincerely,
-t c
Thomas C. Welborn
Chief
Wetlands, Coastal & Ocean Branch
cc: USFWS, Raleigh
NMFS, Pivers Island
NCWRC, Creedmoor
NCDWQ, Raleigh