20100597 Ver 1_Mitigation Bank Proposal Review_20071212

Michael F. Easley, Governor
William G. Ross Jr., Secretary
North Carolina Department of Environment and Natural Resources
Coleen H. Sullins, Director
Division of Water Quality
Memo.
20100597
To: Chris Huysman (Wetland/Natural Resources), Susan Yates (Centex Homes), Amanda Jones
(COE), et. al
From: Alan Johnson
Subject: Six Mile Creek Mitigation Bank, Centex Homes
I have reservations regarding the proposed plan for the enhancement of the wetland and streams
that flow through the site. Prior to visiting the site, this office was under the impression that the
area was more pasture (fescue) similar to the area observed adjacent to the stream (i.e. "A"),
which drains the watershed north of the site. Instead, I observed an area that was much further
along in its ecological succession and a very dynamic system.
Regarding the proposed stream enhancement, the "channels" that flow through the
bottom land/wetla nd do not appear to be developed enough and given the topography they may
not be that permanent. Stream A, which drains the watershed continues to Six Mile Creek, but
due to blockage from sediment aggradations and/or vegetation, a side channel has diverted into
the wetland. This channel then splits into three channels that all flow to Six Mile Creek. One of
these channels was not discharging to the Creek. Another channel was obstructed by what
appeared to be a small beaver dam and was diverted and had cut a new channel. There were
even noticeable areas along the bank of Six Mile Creek that appeared to be points of entry into
the creek due to overflow from the flooding of the wetland.
Also, given that the area was inundated with water and would probably be described as a
freshwater marsh, planting of trees and other vegetation would be limited to around the periphery
of the site, not all 28 acres. It is not certain how much enhancement could actually be
accomplished. The idea was to bring the site to a climax succession, but it isn't clear if this is
necessarily better than allowing the site to go through the natural succession.
In addition these items need to be taken into account:
¦ Six Mile Creek has a state mandated 200 ft. buffer due to the heel splitter
¦ Mecklenburg County has a "SWIM" buffer along both Six Mile Creek and stream A, which
appears to be 100 ft. and 50 ft., respectively.
¦ A sewer easement runs adjacent to Six Mile Creek through the site.
¦ The entire site is within a FEMA flood plain. Northcarolina
Naturally
North Carolina Division of Water Quality 610 East Center Ave., Suite 301 Mooresville, NC 28115 Phone [phone] Customer
Service
Internet: h2o.enr.state. nc.us FAX [phone]-623-
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Given all these parameters, and the general observation that there appears to be no evidence of
any detrimental impact to the wetland or "channels" from the upstream development. It is this
office's opinion that the proposal for stream enhancement credit be denied. The proposal for
wetland enhancement credit be limited to the actual acreage planted/enhanced (2:1 ratio) and that
grade control measures be installed in the "channels" as part of that enhancement. This will
ensure some measure of stability to prevent head cutting of the channels from the point of
discharge at Six Mile Creek and at the point of diversion from stream A.
If you have any questions please let me know.
Thank you
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