20080868 Ver 2_Staff Comments_20081030

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NC Division of Water Quality
401 Oversight and Express Permitting Unit
October 30, 2008
Memorandum
To: John Dorney
From: Tammy Hill and Eric Kulz
Subject: Response to the PCS September 4, 2008 Additional Information Letter
(Wetland/Stream Mitigation Details)
Mitigation ratios
¦ The ratios proposed for wetland and stream mitigation are acceptable to DWQ if they are
determined by the U.S. Army Corps of Engineers to yield adequate functional uplift of
aquatic resources to offset water quality impacts from the proposed mining activity.
DWQ agrees that there is value in restoration activities at Parker Farms, Sections I and J.
However, since water flows southeast from this area, water quality improvements from
these activities are likely to be seen in Bay River (an impaired tributary to Pamlico Sound).
If these areas are included in the mitigation package, DWQ continues to recommend a
higher mitigation ratio per the Guidance on the Use of Compensatory Mitigation in Adjacent
Cataloging Units.
Mitigation plans
DWQ staff have visited all proposed mitigation sites except Jacobs Creek. We have also
received updated mitigation plans for several proposed mitigation projects since our
August 5, 2008 Request for Additional Information. We concur that DWQ has enough
information to evaluate the proposed mitigation package in relation to the proposed impact.
We will work closely with other agencies in evaluating individual mitigation plans as they
are finalized by the applicant.
• The updated mitigation plans have also satisfied our intent with the request for verification
of ecosystem types in 4.A.II.h.
Many of the comments in our August 5, 2008 Request for Additional Information letter have been
addressed by the "Success Criteria for PCS Phosphate Wetland/Stream Mitigation" document
dated October 9, 2008 and received from Jeff Furness via email on October 10, 2008. The
following points summarize these criteria:
Hydrology criteria: continual saturation or inundation for a targeted % of the growing
season based on wetland type
o Headwater wetlands: minimum 12.5%; targeted range 12.5 - 25%
o Bottomland hardwood forested wetlands: minimum 12.5%; targeted 25 - 75%
o Riverine swamp forested wetlands: minimum 75%; targeted 75 - 100%
o Non-riparian wet hardwood flats on mineral soils: minimum 6%
o Non-riparian wet hardwood flats on organic soils: minimum 10%
DWQ Response to PCS 9/4/2008 Additional Info Letter October 30, 2008
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o Area eligible for riparian mitigation credit will be determined using data from well
arrays aligned perpendicularly to headwater valleys in combination with LIDAR
and flow data. DWQ Note: Non-riparian credit may be granted for wetlands in
valleys that do not meet riparian success criteria; however, this decision should
be made by the agencies based upon review of site-specific information and
monitoring results.
Flow monitoring
o Linear flow in riparian headwater systems will be documented through
photographs and observations of active flow, movement of wrack and sediment,
and the development of drainage patterns and channel features.
o The upstream extent of linear flow will be observed visually and noted with a
GPS point.
o These monitoring activities are in line with DWQ's expectations for determining
the length of valley restoration projects eligible for stream and riparian buffer
mitigation credit.
Vegetation criteria
o Wetlands: Minimum 260 5-year old planted woody stems per acre surviving at
end of monitoring period
o Riparian buffers: Minimum 320 5-year old planted woody stems per acre
surviving at end of monitoring period
o Diversity representative of targeted ecosystem types
North Carolina Division of Water Quality; 401 Oversight and Express Permitting Unit
1650 Mail Service Center; Raleigh, NC 27699-1650
2321 Crabtree Blvd., Raleigh, NC 27604-2260
Telephone: [phone]; Fax: [phone]
http://h2o.enr.state.nc.us/wetiands.htmI