20081312 Ver 1_Mitigation Site Visit_20081010

PCS Phosphate Mitigation Success Criteria
Subject: PCS Phosphate Mitigation Success Criteria
From: [e-mail]
Date: Fri, 10 Oct 2008 10:41:59 -0400
To: [e-mail]
CC: [e-mail], [e-mail], [e-mail]
Eric:
Per your request during our meeting in your offices last Friday, attached
is a compilation of the success criteria that we will be applying to our
wetland and stream mitigation projects. Let me know if you have any
questions.
Jeff
(See attached file: PCS Success Criteria.doc)
Jeff Furness
Senior Scientist
PCS Phosphate Co., Inc.
1530 NC Hwy 306 S
Aurora, NC 27806
Ph: [phone]
Fax: [phone]
PCS Success Criteria.doc Content-Type: application/msword
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1 of 1 10/30/2008 1:28 PM
SUCCESS CRITERIA FOR PCS PHOSPHATE WETLAND/STREAM MITIGATION
October 9, 2008
RIPARIAN SUCCESS CRITERIA FROM MEETING WITH D. LEKSON 9/23/08
1) Headwater Stream and riparian wetland success criteria. We spent a lot of
time on this, as David went through the Powerpoint presentation that he put
together and gave to the NC IRT in a meeting last week in Raleigh. The simple
one was credit for stream mitigation length in these headwater valleys - document
flow twice per year for 3 years out of 5 during normal precipitation. Flow can be
documented in several ways, which I believe each of the plans has discussed.
David said that the flow documentation methods we have proposed match pretty
well with what is discussed in RGL 05-05. It is suggested that every time you are
on site and the stream system is flowing, GPS the uppermost point of observable
flow.
Wetland success in the riparian area is a little more complicated, but follows the
direction that we have been heading as of late. Each project should divide stream
length segments into headwater, bottomland hardwood and riverine swamp forest
zones, based on stream order and geomorphic position in the landscape. For
example, segments along 0 and I" order streams would most likely be
headwaters, segments along 2nd order streams may be bottomland hardwood, and
segments along 3`d order or larger may be riverine swamp forest. Most of our
projects will fall into the headwaters and BLH categories.
The success criteria minimum for riparian wetlands in the geomorphic valley in
the headwaters zone is 12.5%, in the BLH zone is 12.5% (this is correct), and in
the riverine swamp forest zone is 75%. The target hydrology range for each zone
is 12.5%-25% for headwaters, 25%-75% for BLH, and 75%-100% for riverine
swamp forest. The width of the riparian wetland available for credit will be based
on where the hydrology percentage drops below the minimum success criteria, as
quantified by the use of perpendicular well arrays across the stream valleys, along
with lidar signatures and as-built valley cross-sections (in other words, we are not
going to get riparian credit for wetlands that are above 12.5% hydrology if those
wetlands are out of the linear valley feature associated with the stream). If the
hydrology percentage drops below the minimum for success, even though the
location still may be within the "valley", it will be considered as being in the
wetland "flats" and will count as non-riparian wetland credit.
There are 4 dimensions to riparian success, according to Lekson. First, is linear
flow, as shown by field indicators of flow. Second is riparian side to side width,
which is determined by the well arrays discussed above. Third is the depth and
connection of surface and groundwater, or the hyperheic zone. This is met by
proposing and having an approved site and construction techniques. In other
words, put back what the site supports, and don't dig a channel where one did not
exist. The fourth dimension is temporal, the growth of vegetation through time.
The difference in definition of riparian and riverine is governed by dominant
water source. Riverine wetlands are dominated by overbank flooding, and
riparian wetlands are dominated by groundwater. Generally, the riparian wetland
zone will be wider than the riverine wetland zone. For PCS, we are only
concerned with riparian wetlands.
PCS has on-site well data from NCPC stream monitoring for Tooley and Jacks
Creeks and Huddles Cut for 2000 (normal rainfall year) collected in the center of
the stream valleys in riverine swamp forest and bottomland hardwood forest,
which is in agreement with hydroperiods, stream order, and geomorphic position
above. PCS also has well data collected from 1991-1993 (during original JD for
NCPC tract), and five wells which were located in or near headwater riparian
areas displayed hydroperiods also in agreement with the hydroperiods, stream
order, and geomorphic position above.
1.1 Hydrology Monitoring [Note: These sections taken from the Sept. 2008
Upper Back Creek mitigation plan, but these pertain to all of the mitigation projects]
Monitoring wells (semi-continuous Ecotones from Remote Data Systems, Inc.) are currently
installed across the site, and distributed in all major mitigation areas of the site. One automated
rain gauge was installed in conjunction with the wells and will be removed during construction
activities and reinstalled after completion of restoration activities. The gauge is/will be installed
in an open area, a minimum of 100 feet from any tall tree or buildings. On site rainfall data will
be used in conjunction with data from the PCS Aurora weather station to determine rainfall
during the monitoring period.
Semi-continuous water level monitoring wells will be installed across the project site
(approximately 1 well per 10 acres for restored wetlands) to document post-restoration water
table conditions. Data from these wells will be downloaded monthly. These data will be used to
assess whether the water table at the project site has been elevated sufficiently to restore wetland
conditions.
In the riparian headwater valleys, semi-continuous monitoring wells will also be installed in
perpendicular arrays across the valley to assist in identification of riparian wetlands and to
increase the density of data points for analysis of hydrographs up and across the valley. Arrays
will be approximately 500 feet apart (along the long axis) for each valley. The center well in
each array will be in the lowest part of the valley and the number of wells in the array will be
dependent upon width and slope of each valley.
Flow in the riparian headwater systems will be documented using a variety of parameters and
simple techniques including photographic evidence of observed active flow conditions and
evidence of past flow conditions including, but not limited to sediment deposits, debris flows,
movement of wrack, sinuosity, braided flow features, and development of channel features. Flow
events will be monitored during the growing and dormant seasons.
1.1.1 Hydrological Success Criteria
For wetland hydroperiods, using the new regional guidance from the USACE, the growing season
for Beaufort County is 28 February to 6 December (WETS table for Beaufort County first/last
freeze date 28 degrees F 50 percent-282 days).
Monitoring data from on-site and off-site reference wells, pre-disturbance well data from impact
sites, and regulatory guidances and procedures were used to develop appropriate hydrologic
success criteria for the riparian and non-riparian wetland areas to be restored. Past well data from
non-riparian mineral flats on the PCS NCPC tract were used to develop the hydrologic success
criteria for non-riparian wetland restoration areas. These data show that the non-riparian areas
that have been or may be impacted as a result of mining activities (thereby requiring mitigation)
exhibited hydroperiods of approximately 6 percent prior to mining disturbances. Therefore, non-
riparian mineral wetland flats will be considered successful with 6 percent or greater
hydroperiods, [Note: For non-riparian wetland flats for projects on organic soils, the hydrology
success criteria will be 10 percent].
1.2 Vegetation Monitoring Plots
Vegetation monitoring plots will be established over approximately one to two percent of the
planted restoration area. Individual plots will be 43 feet x 203 feet in size (0.2 acre). Plots will
be located to represent a range of conditions within the planting zones across the restoration site
and the corner of each plot will be anchored at a semi-continuous monitoring well. The plots will
be oriented from the well corner using a random table of azimuths; however, azimuths may be
slightly adjusted if necessary to avoid obstructions and/or remain within the parcel boundaries or
within a specific zone, etc. Immediately after planting has occurred, planted stems within
vegetation plots will be marked with poles and when leaf out has occurred, each tree/shrub will
be tagged, identified, and counted.
Each monitoring year prior to leaf fall in autumn, planted trees within the plots will be sampled
for survival. At the fifth year, all living stems of woody vegetation within each plot will be
identified and counted, including planted stems and colonized species. Colonized stems will be
tracked separately from the planted trees. General observations will be made during sampling to
describe the survivability of stems outside the vegetation monitoring plots, and other vegetation
planted across the site (permanent seeding, etc.).
1.2.1 Vegetation Success Criteria
Restoration of the vegetation will be deemed successful if at least 260 five-year old trees per acre
(planted woody stems) are alive after 5 years (or the end of the required monitoring, whichever is
later). Riparian buffer restoration will be deemed successful if at least 320 five-year old trees per
acre (planted woody stems) are alive after 5 years (or the end of the required monitoring,
whichever is later). In addition, the diversity of surviving trees will be representative of the
targeted ecosystem types for riparian and non-riparian areas.