ANNUAL REPORT FOR 2010
Little River Bridge Mitigation Site
Moore County
TIP No. R-0210A
Prepared By:
Natural Environment Unit & Roadside Environmental Unit
North Carolina Department of Transportation
December 2010
TABLE OF CONTENTS
SUMMARY...................................................................................................................... 1
1.0 INTRODUCTION.................................................................................................. 1
1.1 PROJECT DESCRIPTION ........................................................................ 1
1.2 PURPOSE ................................................................................................. 1
1.3 PROJECT HISTORY................................................................................. 2
1.4 DEBIT LEDGER ........................................................................................ 3
2.0 HYDROLOGY....................................................................................................... 5
2.1 SUCCESS CRITERIA................................................................................ 5
2.2 HYDROLOGIC DESCRIPTION ................................................................. 5
2.3 RESULTS OF HYDROLOGIC MONITORING........................................... 5
2.3.1 Site Data ......................................................................................... 5
2.3.2 Climatic Data................................................................................... 8
2.4 CONCLUSIONS ........................................................................................ 8
3.0 VEGETATION .................................................................................................... 11
3.1 SUCCESS CRITERIA.............................................................................. 11
3.2 DESCRIPTION OF PLANTED AREAS.................................................... 11
3.3 RESULTS OF VEGETATION MONITORING………………………………12
3.4 CONCLUSIONS ...................................................................................... 12
4.0 OVERALL CONCLUSIONS/RECOMMENDATIONS ......................................... 12
LIST OF FIGURES
Figure 1. Site Location Map ........................................................................................... 4
Figure 2. Monitoring Gauge Location Map ..................................................................... 6
Figure 3. Hydrologic Monitoring Results......................................................................... 9
Figure 4. 30-70 Percentile Graph................................................................................. 10
LIST OF TABLES
Table 1. Debit Ledger..................................................................................................... 3
Table 2. Hydrologic Monitoring Results.......................................................................... 7
Table 3. Hydrologic Monitoring Results (2006-2010) ..................................................... 7
Table 4. Vegetative Monitoring Results (Hardwood Areas).......................................... 11
APPENDICES
APPENDIX A GAUGE DATA GRAPHS
APPENDIX B PHOTO AND VEGETATION PLOT LOCATIONS, SITE PHOTOS
1
SUMMARY
The following report summarizes the monitoring activities that have occurred in 2010 at
the Little River Bridge Mitigation Site. The 2010 monitoring year represents the fifth
year of hydrologic and vegetation monitoring following construction. The site must
demonstrate hydrologic and vegetation success for a minimum of five years or until the
site is deemed successful. The site was constructed to serve as mitigation for impacts
associated with the US 1 Bypass in Moore County.
In February 2006, groundwater monitoring gauges were installed to monitor hydrology
on the site. Four groundwater gauges and one rain gauge were positioned on the
restoration site. There are also three reference gauges that were installed prior to
construction. The reference gauges are located directly adjacent to the constructed site
within the preservation area.
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.
The 2010 monitoring year represents the fifth year for hydrology monitoring. Three of
the four groundwater restoration gauges met the success criteria for 2010 with one of
the gauges recording hydrology for 5.7% of the growing season. The three reference
gauges recorded jurisdictional hydrology above the required 12.5% of the growing
season.
Vegetation monitoring in the restoration area yielded 470 trees/shrubs per acre. This
average is above the minimum success criteria of 260 trees/shrubs per acre for year
five.
The shrub area underneath the Progress Energy distribution line was mowed by a
contractor who was not aware of the mitigation area in April 2010. NCDOT has since
met with Progress Energy on-site in May 2010 and installed signs to make the mowing
contractor aware of the mitigation area. The majority of the shrubs that were mowed
have re-sprouted and it appears that no permanent damage has been done to the site.
NCDOT met with the Resource Agencies on August 12th, 2010 to review and assess
the mowed portion of the site. At that time it was agreed that NCDOT would continue to
monitor the site through the final monitoring year to determine if any permanent
damage had occurred.
Based on the results from the fifth year of monitoring, NCDOT proposes to discontinue
all vegetation and hydrologic monitoring at the Little River Bridge Mitigation Site.
1
1.0 INTRODUCTION
1.1 Project Description
The Little River Bridge Mitigation Site serves as mitigation for T.I.P R-0210A, which
constructed the US 1 Bypass in Moore County (Figure 1). The 14.8-acre site is located
in Moore County 0.75 mile southeast of the town of Vass and is on either side of the
Little River. The site can be accessed via US 1 Business South on the northeastern
site boundary. The site includes 6.4 acres of restoration and 8.4 acres of preservation
of bottomland hardwood forest. Reference areas onsite were utilized to provide
reference data for restoration monitoring.
1.2 Purpose
In order to demonstrate successful mitigation, hydrologic and vegetation monitoring
must be conducted for a minimum of five years or until the site is deemed successful.
Vegetation success criteria states that at least 320 trees/acre must survive through year
three. A ten percent mortality rate will be accepted in year four (288 trees/acre) and
another ten percent in year five, resulting in a required survival rate of 260 trees/acre.
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. This report
includes analyses of hydrologic and vegetation monitoring results, discussions of local
climatic conditions throughout the growing season, and site photographs.
1.3 Project History
January 2006 Site Constructed
February 2006 Site Planted
February 2006 Monitoring Gauges Installed
March-November 2006 Hydrologic Monitoring (Year 1)
June 2006 Vegetation Monitoring (Year 1)
March-November 2007 Hydrologic Monitoring (Year 2)
June 2007 Vegetation Monitoring (Year 2)
March-November 2008 Hydrologic Monitoring (Year 3)
June 2008 Vegetation Monitoring (Year 3)
March-November 2009 Hydrologic Monitoring (Year 4)
June 2009 Vegetation Monitoring (Year 4)
March-November 2010 Hydrologic Monitoring (Year 5)
June 2010 Vegetation Monitoring (Year 5)
3
1.4 Debit Ledger
Table 1. Debit Ledger
Site name Site TIP HUC
River
Basin Division County
Mitigation
Type
As Built
Quantity Available Debit Debit Debit
Little River
Bridge R-0210A 3030004 Cape Fear 8 Moore R-0210A U-3816 B-4584
Riverine
Wetland
Preservation 8.4 0 8.4
Riverine
Wetland
Restoration 6.4 1.07 4.8 0.42 0.11
Note: Debit ledger information up to date as of December 14, 2010.
4
Figure 1. Site Location Map
5
2.0 HYDROLOGY
2.1 Success Criteria
The hydrologic success criteria established for the Little River Bridge Mitigation Site, as
stipulated in the approved mitigation plan and subsequent revisions, 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.
The growing season in Moore County begins on March 23 and ends November 7.
These dates correspond to a 50% probability that air temperature will drop to 28° after
March 23 and before November 71; thus, the growing season is 230 days.
2.2 Hydrologic Description
Four groundwater monitoring gauges were installed within the site’s restoration area
(Figure 2) in February 2006. There are also three reference gauges that were installed
prior to construction in the existing wetlands that are adjacent to the constructed site. A
rain gauge is also located on the site to assist in comparison of the rainfall data
(supplied by the NC State Climate Office) from an official weather station in Carthage.
The groundwater gauges record water levels on a daily basis.
2.3 Results of Hydrologic Monitoring
2.3.1 Site Data
The maximum number of consecutive days that saturation occurred within 12 inches of
the ground surface was determined for each groundwater monitoring gauge. This
number was converted into a percentage of the 230-day growing season (March 23 –
November 7). Table 1 provides the 2010 hydrologic results; Figure 3 is a graphical
representation of these results. Appendix A includes graphs of the data recorded at
each groundwater gauge. Daily rainfall events recorded at the onsite rain gauge are
included on each of the groundwater gauge plots.
1 Soil Conservation Service, Soil Survey of Moore County, North Carolina, 1995.
6
Figure 2. Monitoring Gauge Location Map
7
Table 2. Hydrologic Monitoring Results
Monitoring Gauge < 5% 5-8% 8-12% > 12.5% Actual % Success Dates
LR-GW1+ X 13.9 Mar 23-Apr 23
LR-GW2+ X 21.3 May 6-Jul 4
LR-GW3+ X 15.2 Mar 23-Apr 26
LR-GW4 X 5.7
LR-REF1+ X 13.0 Mar 23-Apr 21
LR-REF2 + X 16.1 Mar 23-Apr 28
LR-REF3+ X 13.5 Mar 23-Apr 22
Shaded gauges are reference gauges.
+Gauges met success during average rainfall months (January, May, and July).
Groundwater monitoring gauge four did not meet the success criterion in 2010. The
close proximity to the Little River may be causing a drawdown effect on the gauge.
NCDOT may need to delineate this area to determine whether or not wetland hydrology
is present in this portion of the site. Hydrologic monitoring results from all five years of
monitoring are presented in Table 3 below.
Table 3. Hydrologic Monitoring Results (2006-2010)
Monitoring
Gauge
2006
Results
2007
Results
2008
Results
2009
Results
2010
Results
LR-GW1 15.4 18.7 27.0 14.8 13.9
LR-GW 2 16.2 7.4 20.9 15.2 21.3
LR-GW 3 14.0 19.6 26.5 15.7 15.2
LR-GW 4 3.9 5.7 7.0 5.7 5.7
LR-REF1 13.2 17.8 23.0 15.7 13.0
LR-REF2 29.4 24.3 27.4 17.8 16.1
LR-REF3 13.2 17.7 21.3 13.9 13.5
Climate
Conditions
Average
Rainfall
Average
Rainfall
Average
Rainfall
Avg./Below
Average
Rainfall
Average
Rainfall
8
2.3.2 Climatic Data
Figure 4 is a comparison of the 2010 monthly rainfall to the historical precipitation
(collected between 1977 and 2009) for Carthage, North Carolina. This comparison
gives an indication of how 2010 relates to historical data in terms of climate conditions.
The NC State Climate Office provided all historical rainfall information. For 2010,
March, April, October and November recorded below average rainfall. The months of
January, May and July recorded average rainfall; while February, June, August and
September recorded above average rainfall. Overall, 2010 was an average rainfall year.
2.4 CONCLUSIONS
The 2010 monitoring year represents the fifth year of hydrologic monitoring for the Little
River Bridge Mitigation Site. Three of the four groundwater restoration gauges met the
success criteria for 2010 with one of the gauges recording hydrology for 5.7% of the
growing season. The three reference gauges recorded jurisdictional hydrology above
the required 12.5% of the growing season.
NCDOT proposes to discontinue hydrologic monitoring at the Little River Bridge
Mitigation Site.
9
Figure 3. Hydrologic Monitoring Results
10
Figure 4. 30-70 Percentile Graph
11
3.0 VEGETATION: LITTLE RIVER BRIDGE MITIGATION SITE
(YEAR 5 MONITORING)
3.1 Success Criteria
The projects success criteria state that at least 320 trees/acre must survive through
year three. A ten percent mortality rate will be accepted in year four (288 trees/acre)
and another ten percent in year five, resulting in a required survival rate of 260
trees/acre.
3.2 Description of Species
The following tree and shrub species were planted in the Wetland Restoration Area:
Tree Area:
Taxodium distichum, Baldcypress
Nyssa aquatica, Water Tupelo
Quercus phellos, Willow Oak
Quercus michauxii, Swamp Chestnut Oak
Shrub Area:
Cephalanthus occidentalis, Buttonbush
Aronia arbutifolia, Red Chokeberry
Cornus amomum, Silky Dogwood
Alnus serrulata, Tag Alder
12
3.3 Results of Vegetation Monitoring
Table 4. Vegetation Monitoring Results (Hardwood Areas)
Site Notes: The shrub area underneath a Progress Energy distribution line was mowed by a contractor
who was not aware of the mitigation area in April 2010. NCDOT met with Progress Energy on site in May
2010 and installed signs to make the mowing contractor aware of the mitigation area. The majority of the
shrubs that were mowed have re-sprouted. Other species noted: Juncus sp., goldenrod, pokeberry,
lespedeza, briars, pine, smartweed, sweetgum, fennel, kudzu, woolgrass, black willow, cattail, red maple,
baccharis, wax myrtle, and various grasses.
3.3 Conclusions
There were two vegetation monitoring plots established throughout the 4.7 acre planting
area. The 2010 vegetation monitoring of the site revealed an average tree density of
470 trees/shrubs per acre. This average is well above the minimum success criteria of
260 trees/shrubs per acre for year five. The Little River Mitigation Site has met the
success criteria for 2010 monitoring year. NCDOT proposes to discontinue vegetation
monitoring at the Little River Mitigation Site.
4.0 OVERALL CONCLUSIONS/RECOMMENDATIONS
The 2010 monitoring year represents the fifth year of hydrologic monitoring for the Little
River Bridge Mitigation Site. Three of the four groundwater restoration gauges met the
success criteria for 2010. The three existing reference gauges recorded jurisdictional
hydrology above the required 12.5% of the growing season.
Vegetation monitoring yielded 470 trees/shrubs per acre. This average is well above
the minimum success criteria of 260 trees/shrubs per acre.
Based on the results from the fifth year of monitoring, NCDOT proposes to discontinue
all vegetation and hydrologic monitoring at the Little River Bridge Mitigation Site.
Plot #
Baldcypress
Water Tupelo
Willow Oak
Swamp Chestnut Oak
Buttonbush
Red Chokeberry
Silky Dogwood
Tag Alder
Total (5 year)
Total (at planting)
Density (Trees/Acre)
1 (T ree s ) 2 4 9 2 8 4 3 6 0 48 7
2 (S h ru bs ) 4 3 2 0 1 2 8 4 2 45 3
A v era g e De n s it y (Tre es & S h rub s /A c re ) 47 0
APPENDIX A
GAUGE DATA GRAPHS
APPENDIX B
PHOTO AND VEGETATION PLOT LOCATIONS AND
SITE PHOTOS
Little River Bridge
Photo 1 Photo 2
Photo 3 Photo 4
June 2010
APPENDIX A
GAUGE DATA GRAPHS