Annual report for ... Long Creek mitigation site, Mecklenburg County, project no. 8.U672204, TIP no. R-2248

              ANNUAL REPORT FOR 2008
Long Creek Mitigation Site
Mecklenburg County
TIP No. R-2248
Prepared By:
Natural Environment Unit & Roadside Environmental Unit
North Carolina Department of Transportation
December 2008
TABLE OF CONTENTS
SUMMARY...................................................................................................................... 1
1.0 INTRODUCTION.................................................................................................. 2
1.1 Project Description..................................................................................... 2
1.2 Purpose ..................................................................................................... 2
1.3 Project History ........................................................................................... 4
2.0 HYDROLOGY....................................................................................................... 5
2.1 Success Criteria......................................................................................... 5
2.2 Hydrologic Description............................................................................... 5
2.3 Results of Hydrologic Monitoring ............................................................... 7
2.3.1 Site Data ......................................................................................... 7
2.3.2 Climatic Data................................................................................... 7
2.4 Conclusions ............................................................................................... 7
3.0 VEGETATION: LONG CREEK MITIGATION SITE ........................................... 11
3.1 Success Criteria....................................................................................... 11
3.2 Description of Species ............................................................................. 11
3.3 Results of Vegetation Monitoring ............................................................. 12
3.4 Conclusions ............................................................................................. 12
4.0 OVERALL CONCLUSIONS AND RECOMMENDATIONS............................ 12-13
LIST OF FIGURES
Figure 1. Site Location Map ...................................................................................... 3
Figure 2. Gauge Location Map.................................................................................. 6
Figure 3. Hydrologic Monitoring Gauge Results ....................................................... 9
Figure 4. 30-70 Percentile Graph............................................................................ 10
LIST OF TABLES
Table 1. Hydrologic Monitoring Results ................................................................... 8
Table 2. Vegetation Monitoring Results ................................................................. 12
APPENDICES
APPENDIX A GAUGE DATA GRAPHS
APPENDIX B SITE PHOTOS/VEGETATION PLOT & PHOTO LOCATIONS
1
SUMMARY
The Long Creek Mitigation Site is located in Mecklenburg County and was constructed
in 1996. In order to receive mitigation credit, the site must meet jurisdictional success
criteria for both wetland hydrology and vegetation for three consecutive years or until
the site is deemed successful. The following report details the monitoring activities
during the 2008 growing season. The 2008 data represent results from the eleventh
year of hydrologic monitoring.
The daily rainfall data depicted on the gauge data graphs was recorded from an onsite
rain gauge that was installed on May 4, 2000. Additional rainfall data used for the 30-70
graph was taken from a gauge in Charlotte from the NC State Climate Office.
Hydrologic success criteria are based on the approved mitigation plan and require that
the site demonstrate saturation or inundation within 12 inches of the soil surface for a
consecutive 12.5% of the growing season during years of normal rainfall.
For the eleventh year of hydrologic monitoring, eleven of the eighteen groundwater
gauges met the success criteria for jurisdictional hydrology (saturation within 12” of the
surface for greater than 12.5% of the growing season). Four gauges reported
saturation below 5% and three gauges had data in the 5 - 8% range. All four surface
water gauges indicated periodic inundation during the growing season.
The status of the vegetation monitoring at the Long Creek Mitigation Site was discussed
at the 2003 annual monitoring meeting. It was agreed that vegetation monitoring would
be discontinued until completion of the Charlotte Outer Loop (I-485). Upon completion
of the highway project, vegetation monitoring would resume for one year. The site was
visually monitored from 2003 to 2007. The Charlotte Outer Loop (I-485) was completed
in December 2008, and traffic is now open on the roadway. For the 2008-monitoring
year, the site was monitored for vegetation. The vegetation monitoring revealed an
average tree density of 622 trees per acre. This average is well above the minimum
success criteria of 320 trees per acre.
Based on eleven years of monitoring, NCDOT proposes to discontinue all monitoring
activities at the Long Creek Mitigation Site for hydrology and vegetation. NCDOT is in
the process of identifying areas of site that have routinely not met optimum hydrology
with state and federal regulatory agencies. Upon review there is no relevant
remediation that would increase hydrologic inputs to the deficit areas. Once these
areas are quantified, NCDOT will develop a proposal to rectify outstanding mitigation
requirements.
2
1.0 INTRODUCTION
1.1 Project Description
Located in Mecklenburg County, the Long Creek Mitigation Site encompasses
approximately 156 acres. It is situated off of Beatties Ford Road (SR 2074) and will be
bisected by Charlotte Outer Loop (I-485) (Figure 1). This project will provide
compensatory mitigation for wetland impacts associated with sections of the proposed
Charlotte Outer Loop (I-485).
The Long Creek Site was designed to restore bottomland hardwood forest wetlands. It
was constructed in December 1996 and 37 acres of the planting occurred in 1997. A
five-acre portion, consisting of the former haul roads, was planted in early 1998.
Groundwater, surface water, and rain gauges were installed in 1998.
1.2 Purpose
Monitoring of the Long Creek Site is required to demonstrate successful mitigation. The
success of a wetland site is based primarily on federal guidelines for wetland mitigation,
which include minimum standards for hydrologic conditions and vegetation survival.
Both hydrologic and vegetation monitoring is conducted throughout the growing season;
success criteria must be met for three consecutive years. The following report details
the results of the hydrologic and vegetation monitoring for 2008 at the Long Creek
Mitigation Site.
3
Figure 1. Site Location Map
4
1.3 Project History
December 1996 Grading Construction
March 1997
Site Planted (Except for approximately 5 AC. of
Haul Roads-to be Planted by March 1998)
September 1997 Vegetation Monitoring (1 yr.)
October 1997 Monitoring Gauges Installed
March 1998 Haul Roads Planted
March-November 1998 Hydrologic Monitoring (1 yr.)
September 1998 Vegetation Monitoring (2 yr.)
March- November 1999 Hydrologic Monitoring (2 yr.)
September 1999 Vegetation Monitoring (3 yr.)
March- November 2000 Hydrologic Monitoring (3 yr.)
September 2000 Vegetation Monitoring (4 yr.)
March 2001 Site Maintenance
March- November 2001 Hydrologic Monitoring (4 yr.)
June 2001 Vegetation Monitoring (5 yr.)
March- November 2002 Hydrologic Monitoring (5 yr.)
August 2002 Vegetation Monitoring (6 yr.)
March- November 2003 Hydrologic Monitoring (6 yr.)
October 2003 Photograph Monitoring (7 yr.)
October 2004 Nuisance Tree Species Cut
November 2004 Photograph Monitoring (8 yr.)
March- November 2004 Hydrologic Monitoring (7 yr.)
September 2005 Photograph Monitoring (9 yr.)
March- November 2005 Hydrologic Monitoring (8 yr.)
5
July 2006 Photograph Monitoring (10 yr.)
March- November 2006 Hydrologic Monitoring (9 yr.)
September 2007 Photograph Monitoring (11 yr.)
March- November 2007 Hydrologic Monitoring (10 yr.)
September 2008 Vegetation Monitoring (12 yr.)
March- November 2008 Hydrologic Monitoring (11 yr.)
2.0 HYDROLOGY
2.1 Success Criteria
In accordance with federal guidelines for wetland mitigation, the success criteria for
hydrology state that areas must be inundated or saturated (within 12 inches of the
surface) by surface or groundwater for at least a consecutive 12.5% of the growing
season. Areas inundated for less than 5% of the growing season are always classified
as non-wetlands. Areas inundated between 5% and 12.5% of the growing season can
be classified as wetlands depending upon such factors as the presence of wetland
vegetation and hydric soils.
The growing season in Mecklenburg County begins March 22 and ends November 11
(235 days). These dates correspond to a 50% probability that air temperatures will not
drop below 28°F or lower after March 22 and before November 11.1 Minimum wetland
hydrology is required for at least 12.5% of this growing season; for Mecklenburg
County, 12.5% equals 29 consecutive days.
2.2 Hydrologic Description
Eighteen groundwater gauges, four surface water gauges, and two rain gauges were
installed in October 1997 (Figure 2). Daily readings of the groundwater depth were
taken throughout the growing season. The rainfall data used to analyze the site’s water
level data are from onsite rain gauges.
The Long Creek Site was designed to function with rainfall and surface water runoff, as
its primary hydrologic inputs. The current monitoring gauge configuration was
implemented to capture the influence of rainfall and surface water runoff, upon
completion of the construction.
1 Natural Resources Conservation Service, Soil Survey of Mecklenburg County, North Carolina, p.61.
6
Figure 2. Gauge Location Map
Legend
7
2.3 Results of Hydrologic Monitoring
2.3.1 Site Data
The maximum number of consecutive days that the groundwater was within twelve
inches of the surface was determined for each gauge. This number was converted into
a percentage of the 235-day growing season. The results are presented in Table 1.
Appendix A includes water depth for each groundwater and surface gauge.
Precipitation is shown on each graph as bars. These graphs show the response at
each monitoring location of the groundwater level to specific rainfall events. The
maximum number of consecutive days is noted on each graph.
2.3.2 Climatic Data
Figure 4 is a comparison of 2007 and 2008 monthly rainfall to historical precipitation for
the area. This comparison indicates if 2008 was “average” in terms of climate
conditions by comparing the rainfall to that of historical rainfall (data collected between
1977 and 2008). The NC State Climate Office provided all historical data.
For 2008; January and October recorded below average rainfall for the site. The
months of February, March, April, May, June, July, September, November, and
December recorded average rainfall, while the month of August experienced above
average rainfall. Overall, 2008 was experienced an average rainfall year.
2.4 Conclusion
For the eleventh hydrologic monitoring year, eleven of the eighteen groundwater
gauges met the success criteria for optimum jurisdictional hydrology (saturation within
12” of the surface for more than 12.5% of the growing season). Four gauges reported
saturation below 5% of the growing season, while three gauges reported marginal
hydrology between 5% - 8% of the growing season. All four surface water gauges
indicated periodic inundation during the growing season after rainfall events.
NCDOT proposes to discontinue monitoring the site for hydrology.
8
Table 1. Hydrologic Monitoring Results
Monitoring
Gauge
<5% 5-8% 8-12.5% >12.5% Actual % Success Dates
LCW-1+ r 31.1 March 22-June 2
LCW-2 r 4.7
LCW-3 r 5.1 April 5-April 16
LCW-4+ r 13.6 March 22-April 22
LCW-7+ r 14.0 March 22-April 23
LCW-9 r 1.7
LCW-10+ r 13.6 March 22-April 22
LCW-11 r 6.8 April 5-April 20
LCW-13 r 7.2 April 9-April 25
LCW-14+ r 13.2 March 22- April 21
LCW-15+ r 14.9 March 22- April 25
LCW-16 r 2.1
LCW-17+ r 33.6
March 22-June 8
June 23-July 21
Aug 21-Oct 31
LCW-18 r 4.7
LCW-20+ r 14.9 March 22-April 25
LCW-22+ r 22.1
March 22-May 12
Sept 11-Oct 11
LCW-23+ r 14.0 March 22- April 23
LCW-24+ r 15.3
March 22- April 24
Sept 11-Oct 16
+Gauge met success during an average rainfall month (March, April, May, June, July,
September, and November).
Specific Gauge Problems:
  Gauge (LCW-13) experienced gauge malfunctions at the beginning of the
growing season and was replaced April 8, 2008.
9
10
Figure 4. 30-70 Percentile Graph
Long Creek
Figure 4 (30-70 Percentile Graph)
Charlotte, NC
4.1
2.1
2.7
2.1
2.3
2.9
3.6
9.8
2.6
3.2
0.5
3.7
1.3
3.8
0
2
4
6
8
10
12
Nov-07 Dec-07 Jan-08 Feb-08 Mar-08 Apr-08 May-08 Jun-08 Jul-08 Aug-08 Sep-08 Oct-08 Nov-08 Dec-08
DATE
Precipitation (in.)
2007 Rainfall 2008 Rainfall
30th Percentile
70th Percentile
3.0 VEGETATION: LONG CREEK MITIGATION SITE
(YEAR 12 MONITORING)
3.1 Success Criteria
The success criteria state that there must be a minimum mean density of 320 trees per
acre of approved target species surviving for at least three years.
3.2 Description of Species
The following tree species were planted in the wetland restoration area:
Fraxinus pennsylvanica, Green Ash
Fraxinus caroliniana, Carolina Ash
Betula nigra, River Birch
Quercus phellos, Willow Oak
Liriodendron tulipifera, Tulip Poplar
Quercus michauxii, Swamp Chestnut Oak
Quercus falcata var. pagodaefolia, Cherrybark Oak
Ulmus americana, American Elm
3.3 Results of Vegetation Monitoring
Table 2. Vegetation Monitoring Results
Plot # (Type)
Green Ash
Carolina Ash
Cherrybark Oak
Swamp. Chestnut
Oak
American Elm
Tulip Poplar
River Birch
Willow Oak
Total (12 Year)
Total (at planting)
Density (Trees/Acre)
1 (BLH) 9 6 7 1 8 31 35 602
2 (BLH) 10 2 6 5 2 10 35 35 680
3 (BLH) 6 13 7 4 3 33 35 641
4 (BLH) 12 6 2 10 5 35 35 680
5 (BLH) 10 6 5 2 1 1 25 35 496
6 (BLH) 8 5 2 9 2 7 33 35 641
AVERAGE DENSITY 622
Site Notes: Other species noted: sycamore, sweetgum, briars, cedar, dogwood, poison ivy, and
various other wetland species.
3.4 Conclusions
Approximately 37 acres of this site were planted in bottomland hardwoods in March
1997. The remaining 5 acres of the site were planted in March 1998. There were six
vegetation monitoring plots established throughout the planted areas. The 2008
vegetation monitoring revealed an average tree density of 622 trees per acre. This
average is well above the minimum success criteria of 320 trees per acre after three
years. NCDOT proposes to discontinue monitoring at the site for vegetation.
4.0 OVERALL CONCLUSIONS AND RECOMMENDATIONS
For the eleventh hydrologic monitoring year, eleven of the eighteen groundwater
gauges met the success criteria for jurisdictional hydrology (saturation within 12” of the
surface for greater than 12.5% of the growing season). Four gauges reported saturation
below 5% and three gauges were in the 5 - 8% range. All four surface water gauges
indicated periodic inundation during the growing season.
For the 2008-monitoring year, the site was also monitored for vegetation. The
vegetation monitoring revealed an average tree density of 622 trees per acre. This
average is well above the minimum success criteria of 320 trees per acre.
The construction activity involved with The Charlotte Outer Loop (I-485), which bisects
the Long Creek Mitigation Site, was completed in December 2008. Currently all
hydrologic features associated with the roadway are functioning, as surface water is
directed across the mitigation site prior to entering Long Creek.
Due to the extensive monitoring at the Long Creek Mitigation Site dating back to the mid
nineties, NCDOT is in the process of identifying areas of site that have routinely not met
optimum wetland hydrology with environmental agencies. Once these areas are
quantified, NCDOT will develop a proposal to reconcile the permits, as well as any
outstanding mitigation credits at the site.
APPENDIX A
GAUGE DATA GRAPHS
APPENDIX B
SITE PHOTOS/VEGETATION PLOT & PHOTO LOCATIONS
Long Creek
Photo 1 Photo 2
Photo 3 Photo 4
Photo 5 Photo 6
September 2008