Annual report for... Sawmill mitigation site, Craven County, project no. 8.1170801, TIP no. B-2531WM |
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ANNUAL REPORT FOR 2007 Sawmill Mitigation Site Craven County TIP No. B-2531WM Prepared By: Natural Environment Unit & Roadside Environmental Unit North Carolina Department of Transportation December 2007 TABLE OF CONTENTS SUMMARY...................................................................................................................... 1 1.0 INTRODUCTION.................................................................................................. 2 1.1 Project Description..................................................................................... 2 1.2 Purpose ..................................................................................................... 2 1.3 Project History ........................................................................................... 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................................................................................... 7 2.4 Conclusions ............................................................................................... 7 3.0 VEGETATION .................................................................................................... 11 3.1 Success Criteria....................................................................................... 11 3.1.1 Bottomland Hardwood Area .......................................................... 11 3.1.2 Marsh Area ................................................................................... 11 3.2 Description of Species ............................................................................. 11 3.3 Results of Vegetation Monitoring……………………………….................. 12 3.4 Conclusions ............................................................................................. 14 3.4.1 Bottomland Hardwood Area .......................................................... 14 3.4.2 Marsh Area ................................................................................... 14 4.0 OVERALL CONCLUSIONS/RECOMMENDATIONS.......................................... 14 LIST OF FIGURES Figure 1. Site Location Map ........................................................................................... 4 Figure 2. Gauge Location Map....................................................................................... 6 Figure 3. 2006 Hydrologic Monitoring Gauge Results .................................................... 9 Figure 4. 30-70 Percentile Graph ................................................................................. 10 LIST OF TABLES Table 1. Hydrologic Monitoring Results.......................................................................... 7 Table 2. Hydrologic Monitoring Results (2003-2007) ..................................................... 7 Table 3. Vegetative Monitoring Statistics (Hardwood Areas) ........................................ 12 Table 4. Vegetative Monitoring Statistics (Marsh Areas).............................................. 13 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 the 2007-year at the Sawmill Mitigation Site. The 2007-year represents the fifth year of hydrology 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 US17 Neuse River Bridge in New Bern. In May 2003, surface water and groundwater gauges were installed to monitor hydrology on the site. Three separate gauge sets, each with one surface and one groundwater gauge, were positioned on the mitigation site. There are also two reference gauge sets that were installed prior to construction. One reference set is located offsite and the other set is 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 hydrologic frequency, duration, and depth consistently within 10% of the hydrology of the reference areas. The 2007-year represents the fifth year of hydrologic monitoring for the Sawmill Mitigation Site. The three groundwater restoration gauges were compared to the two existing reference gauges. Groundwater gauge S-GW5 experienced numerous gauge malfunctions throughout the growing season so no viable conclusions can be taken from its data. Groundwater restoration gauge S-GW3 and S-GW4 indicated that hydrology was not within 10% of reference gauges S-GW1 and S-GW2. It should be noted that it was a below average rainfall year and during such a low rainfall year we would not expect to meet the 10% criteria. The three surface water gauges indicated inundation patterns similar to that of Reference Gauge S-SG2 but showed periods of dryness. Vegetation monitoring in the hardwood area yielded 541 trees per acre. This average is above the minimum success criteria of 320 trees per acre. Supplemental planting of swamp blackgum in January 2004 increased the counts in each plot. For the marsh grass area, the target species and scale values were 100% and 4.5, respectively. NCDOT proposes to discontinue monitoring at the Sawmill Mitigation Site. 2 1.0 INTRODUCTION 1.1 Project Description The Sawmill Mitigation Site serves (entirely) as mitigation for the US17 Neuse River Bridge in New Bern (Figure 1). Situated adjacent to the new bridge alignment, the 4.07- acre site includes both preservation and restoration of brackish tidal marsh as well as tidal cypress-gum swamp. Reference areas, both onsite and offsite, are 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 are based on the National Marine Fisheries Service guidelines. Hydrologic success criteria are based on the approved mitigation plan and require that the site demonstrate hydrologic frequency, duration, and depth consistently within 10% of the hydrology of the reference areas. Included in this report are analyses of hydrologic and vegetation-monitoring results, discussions of local climate conditions throughout the growing season, and site photographs. 3 1.3 Project History 2002 Reference Gauges Installed March 2003 Site Constructed April 2003 Site Planted May 2003 Monitoring Gauges Installed May-November 2003 Hydrologic Monitoring (Year 1) July 2003 Hardwood Vegetation Monitoring (Year 1) July 2003 Marsh Vegetation Monitoring (Year 1) March-November 2004 Hydrologic Monitoring (Year 2) June 2004 Hardwood Vegetation Monitoring (Year 2) June 2004 Marsh Vegetation Monitoring (Year 2) March-November 2005 Hydrologic Monitoring (Year 3) June 2005 Hardwood Vegetation Monitoring (Year 3) June 2005 Marsh Vegetation Monitoring (Year 3) March-November 2006 Hydrologic Monitoring (Year 4) June 2006 Hardwood Vegetation Monitoring (Year 4) June 2006 Marsh Vegetation Monitoring (Year 4) June 2007 Hardwood Vegetation Monitoring (Year 5) June 2007 Marsh Vegetation Monitoring (Year 5) March-November 2007 Hydrologic Monitoring (Year 5) 4 Figure 1. Site Location Map 5 2.0 HYDROLOGY 2.1 Success Criteria The hydrologic success criteria established for the Sawmill Mitigation Site, as stipulated in the approved mitigation plan and subsequent revisions, require that the site demonstrate hydrologic frequency, duration, and depth consistently within 10% of the hydrology of the reference areas. The site-specific criteria vary from current federal guidelines that require a site to be inundated or saturated (within 12” of the surface) by surface or groundwater for a consecutive period amounting to 12.5% of the growing season. The growing season in Craven County begins on March 18 and ends November 14. The dates correspond to a 50% probability that air temperature will drop to 28° after March 18 and before November 141; thus, the growing season is 242 days. Local climate must represent normal conditions for the area. 2.2 Hydrologic Description Wind-driven tides are the primary hydrologic input at the Sawmill Site; therefore, three sets of gauges were installed within the site’s restoration area (Figure 2) in May 2003. Each set includes one surface water gauge and one groundwater-monitoring gauge. There are also two reference gauge sets that were installed prior to construction. One reference set is located offsite and the other set is located directly adjacent to the constructed site, within the preservation area. No rain gauge is located on the site, so rainfall data (supplied by the NC State Climate Office) from an official weather station in New Bern is used to supplement the site data. The surface gauges record surface water levels every three hours, while 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 242-day growing season (March 18 – November 14). Table 1 provides the 2007 hydrologic results; Figure 3 is a graphical representation of these results. Appendix A includes graphs of the data recorded at each groundwater and surface water gauge. Daily rainfall events recorded at the official weather station in New Bern are included on each of the groundwater gauge plots. 1 Soil Conservation Service, Soil Survey of Craven County, North Carolina, 1989. 6 7 Table 1. Hydrologic Monitoring Results Monitoring Gauge Within 10% Actual % Dates of Success S-GW1 (Offsite) (REF) r 100.0 March 18-Nov 14 S-GW2 (Onsite) (REF) r 100.0 March 18-Nov 14 S-GW3 28.0 September 9-Nov 14 S-GW4 45.0 March 18-July 05 S-GW5 36.0 March 18-June 12 Shaded gauges are reference gauges. Specific Gauge Problems: S-GW5: The gauge experienced numerous malfunctions (June 13- September 12). Table 2. Hydrologic Monitoring Results (2003-2007) Monitoring Gauge 2003 Results 2004 Results 2005 Results 2006 Results 2007 Results S-GW1 (Offsite) (REF) 75.8 94.2 60.3 97.9 100.0 S-GW2 (Onsite) (REF) 75.8 100.0 100.0 68.2 100.0 S-GW3 75.8 49.2 71.5 100.0 28.0 S-GW4 75.8 100.0 95.0 100.0 45.0 S-GW5 68.2 50 78.1 100.0 36.0 2.3.2 Climatic Data Figure 4 is a comparison of the 2007 monthly rainfall to the historical precipitation (collected between 1977 and 2007) for New Bern, North Carolina. This comparison gives an indication of how 2007 relates to historical data in terms of climate conditions. The NC State Climate Office provided all local rainfall information. For the 2007-year; April and July experienced above average rainfall. The months of March, May, August, and November recorded below average rainfall, while January, February, June, September, and October recorded average rainfall. Overall, 2007 is considered to be a below average rainfall year. 2.4 Conclusions The 2007-year represents the fifth year of hydrologic monitoring for the Sawmill Mitigation Site. The three groundwater restoration gauges were compared to the two existing reference gauges. Groundwater gauge S-GW5 experienced numerous gauge malfunctions throughout the growing season so no viable conclusions can be taken from its data. Groundwater restoration gauge S-GW3 and S-GW4 indicated that 8 hydrology was not within 10% of reference gauges S-GW1 and S-GW2. The three surface water gauges indicated inundation patterns similar to that of Reference Gauge S-SG2 but show periods of dryness. NCDOT proposes to discontinue monitoring at the Sawmill Mitigation Site. 9 10 Figure 4. 30-70 Percentile Graph Sawmill 30-70 Percentile Graph New Bern, NC 0 1 2 3 4 5 6 7 8 9 Nov 06' Dec 06' Jan 07' Feb 07' Mar 07' Apr 07' May Jun 07' Jul 07' Aug 07' Sep 07' Oct 07' Nov 07' Date Precipitation (in) 2006 Rainfall 2007 Rainfall 30 Percentile 70 Percentile 70 Percentile 30 Percentile Missing Data 11 3.0 VEGETATION: SAWMILL MITIGATION SITE (YEAR 5 MONITORING) 3.1 Success Criteria 3.1.1 Bottomland Hardwood Area The success criteria state that at least 320 stems per acre must survive after the completion of the third growing season and 240 stems per acre after the fifth growing season. If the desired vegetation has not been established, NCDOT will notify the appropriate agencies and will implement corrective measures. 3.1.2 Marsh Grass Area The vegetative success of the marsh portion of the wetland site will be determined in accordance with NMFS Guidelines. Monitoring plots found to be located within the open water channel will not be evaluated, and will not count toward the final count of plots. The vegetation component of the wetland site will be deemed successful if the following criteria are met: 1. At year five, the average of all plots should have a scale value of 5 (>75% vegetative cover) consisting of wetland herbaceous species, not including any invasive species. 2. A minimum of 70% of the plots shall contain the target (planted) species. 3.2 Description of Species The following tree species were planted in the Wetland Restoration Area: Taxodium distichum, Bald cypress Fraxinus pennsylvanica, Green Ash Quercus lyrata, Overcup Oak Nyssa aquatica, Water Tupelo Nyssa sylvatica var. biflora, Swamp Blackgum The following marsh grass species was planted in the Marsh Grass Area: Spartina cynosuroides, Big Cordgrass 12 3.3 Results of Vegetation Monitoring Table 3. Vegetative Monitoring Statistics (Hardwood Areas) Site Notes: Pluchea sp., woolgrass, goldenrod, fennel, wax myrtle, sedge and Juncus sp. Heavy cattails and black willow noted on site. Overcup oaks were noted around the perimeter of plot 1. Plot # Baldcypress Green Ash Overcup Oak Swamp Blackgum Water Tupelo Total (4 year) Total (at planting) Density (Trees/Acre) 1 9 7 4 17 37 48 524 2 2 2 1 0 3 4 2 4 1 5 0 5 5 8 5 4 1 A v e r a g e D e n s ity ( T r e e s /A c r e ) 13 Table 4. Vegetative Monitoring Statistics (Marsh Areas) Plot # Scale Factor Big Cordgrass Frequency Comments 1 4.0 Juncus sp., Black Willow 2 4.0 Juncus sp. 3 5.0 4 5.0 5 5.0 Juncus sp. 6 3.0 Black Willow, Baccharis 7 4.0 Black Willow 8 5.0 Vine, Baccharis 9 4.0 Black Willow 10 4.0 Pennywort, Cattail 11 5.0 12 5.0 13 4.0 Vine 14 5.0 15 5.0 Juncus sp. 16 5.0 Black Willow 17 5.0 Black Willow 18 5.0 19 5.0 20 4.0 Juncus sp., Vine, Pennywort Frequency (Percentage of Plots w/ Desired Species) 100.0% Sum Scale Value 91.0 Total Number of Plots 20 Vegetative Cover (Scale Value) 4.5 Site Notes: The following species were also noted in the monitoring plots. The number of plots the species were found in is following the species in parentheses (i.e. black willow was noted in 6 plots): black willow (6), Juncus sp., (5), cattail (1), pennywort (1), baccharis (2), and vines (2). 14 3.4 Conclusions 3.4.1 Bottomland Hardwood Area There were 2 hardwood vegetation monitoring plots established throughout the 2.4 acre planting area. Swamp blackgum was supplementally planted throughout the site in January 2004, therefore at planting counts increased for each plot. The 2007 vegetation monitoring of the site revealed an average tree density of 541 trees per acre. This average is well above the minimum success criteria of 240 trees per acre. NCDOT proposes to discontinue hardwood vegetation monitoring at the Sawmill Mitigation Site. 3.4.2 Marsh Area • Percent Frequency of Target Species (planted species) 100% Frequency of 70% required. • Vegetative Cover Scale Value 4.5 Scale Value of 5 required for year 5. Of the 4.07 acres of this site, approximately 0.78 acres involved marsh grass planting. There were 20 random plots established throughout the planting area. These plots were located with GPS. Based upon the percent frequency and the scale value, the marsh grass area is on track for the fifth year of monitoring. NCDOT proposes to discontinue marsh grass monitoring at the Sawmill Mitigation Site. 4.0 OVERALL CONCLUSIONS/RECOMMENDATIONS The 2007-year represents the fifth year of hydrologic monitoring for the Sawmill Mitigation Site. The three groundwater restoration gauges were compared to the two existing reference gauges. Groundwater gauge S-GW5 experienced numerous gauge malfunctions throughout the growing season so no viable conclusions can be taken from its data. Groundwater restoration gauge S-GW3 and S-GW4 indicated that hydrology was not within 10% of reference gauges S-GW1 and S-GW2. The three surface water gauges indicated inundation patterns similar to that of Reference Gauge S-SG2 but show periods of dryness. Vegetation monitoring in the hardwood area yielded 541 trees per acre. This average is above the minimum success criteria of 320 trees per acre. Supplemental planting of swamp blackgum in January 2004 increased the counts in each plot. For the marsh grass area, the target species and scale values were 100% and 4.5, respectively. NCDOT proposes to discontinue all monitoring in 2008. APPENDIX A GAUGE DATA GRAPHS APPENDIX B PHOTO AND VEGETATION PLOT LOCATIONS, SITE PHOTOS Sawmill Photo 1 Photo 2 Photo 3 Photo 4 Photo 5 Photo 6 June 2007 APPENDIX A GAUGE DATA GRAPHS Sawmill S-GW1 Offsite Reference -20 -15 -10 -5 0 5 10 15 20 01-Jan-07 15-Jan-07 29-Jan-07 12-Feb-07 26-Feb-07 12-Mar-07 26-Mar-07 09-Apr-07 23-Apr-07 07-May-07 21-May-07 04-Jun-07 18-Jun-07 02-Jul-07 16-Jul-07 30-Jul-07 13-Aug-07 27-Aug-07 10-Sep-07 24-Sep-07 08-Oct-07 22-Oct-07 05-Nov-07 19-Nov-07 03-Dec-07 17-Dec-07 31-Dec-07 Date Groundwater (in) 0 0.5 1 1.5 2 2.5 3 3.5 4 Precipitation (in) Rainfall S-GW1 9BEB426 (in) Required Depth Beginning of growing season End of growing season 242 Days Sawmill S-GW2 Onsite Reference -20 -15 -10 -5 0 5 10 15 20 01-Jan-07 15-Jan-07 29-Jan-07 12-Feb-07 26-Feb-07 12-Mar-07 26-Mar-07 09-Apr-07 23-Apr-07 07-May-07 21-May-07 04-Jun-07 18-Jun-07 02-Jul-07 16-Jul-07 30-Jul-07 13-Aug-07 27-Aug-07 10-Sep-07 24-Sep-07 08-Oct-07 22-Oct-07 05-Nov-07 19-Nov-07 03-Dec-07 17-Dec-07 31-Dec-07 Date Groundwater (in) 0 0.5 1 1.5 2 2.5 3 3.5 4 Precipitation (in) Rainfall S-GW2 A28BC2A (in) Required Depth Beginning of growing season End of growing season 242 Days Sawmill S-GW3 -30 -25 -20 -15 -10 -5 0 5 10 15 20 01-Jan-07 15-Jan-07 29-Jan-07 12-Feb-07 26-Feb-07 12-Mar-07 26-Mar-07 09-Apr-07 23-Apr-07 07-May-07 21-May-07 04-Jun-07 18-Jun-07 02-Jul-07 16-Jul-07 30-Jul-07 13-Aug-07 27-Aug-07 10-Sep-07 24-Sep-07 08-Oct-07 22-Oct-07 05-Nov-07 19-Nov-07 03-Dec-07 17-Dec-07 31-Dec-07 Date Groundwater (in) 0 0.5 1 1.5 2 2.5 3 3.5 4 Precipitation (in) Rainfall S-GW3 9BEBFF0 (in) Required Depth Beginning of growing season End of growing season 43 Days 24 Days 17 Days 67 Days 30 Days Sawmill S-GW4 -20 -15 -10 -5 0 5 10 15 20 01-Jan-07 15-Jan-07 29-Jan-07 12-Feb-07 26-Feb-07 12-Mar-07 26-Mar-07 09-Apr-07 23-Apr-07 07-May-07 21-May-07 04-Jun-07 18-Jun-07 02-Jul-07 16-Jul-07 30-Jul-07 13-Aug-07 27-Aug-07 10-Sep-07 24-Sep-07 08-Oct-07 22-Oct-07 05-Nov-07 19-Nov-07 03-Dec-07 17-Dec-07 31-Dec-07 Date Groundwater (in) 0 0.5 1 1.5 2 2.5 3 3.5 4 Precipitation (in) Rainfall S-GW4 9DE53A2 (in) Required Depth Beginning of growing season End of growing season 110 Days 41 Days 80 Days Sawmill S-GW5 -20 -15 -10 -5 0 5 10 15 20 01-Jan-07 15-Jan-07 29-Jan-07 12-Feb-07 26-Feb-07 12-Mar-07 26-Mar-07 09-Apr-07 23-Apr-07 07-May-07 21-May-07 04-Jun-07 18-Jun-07 02-Jul-07 16-Jul-07 30-Jul-07 13-Aug-07 27-Aug-07 10-Sep-07 24-Sep-07 08-Oct-07 22-Oct-07 05-Nov-07 19-Nov-07 03-Dec-07 17-Dec-07 31-Dec-07 Date Groundwater (in) 0 0.5 1 1.5 2 2.5 3 3.5 4 Precipitation (in) Rainfall S-GW5 9DE5829 (9DE6718) (in) Required Depth Data Logger Failure Beginning of growing season End of growing season 87 Days 63 Days Sawmill S-SG1 Offsite Reference -1 0 1 2 3 4 5 01-Jan-07 15-Jan-07 29-Jan-07 12-Feb-07 26-Feb-07 12-Mar-07 26-Mar-07 09-Apr-07 23-Apr-07 07-May-07 21-May-07 04-Jun-07 18-Jun-07 02-Jul-07 16-Jul-07 30-Jul-07 13-Aug-07 27-Aug-07 10-Sep-07 24-Sep-07 08-Oct-07 22-Oct-07 05-Nov-07 19-Nov-07 03-Dec-07 17-Dec-07 31-Dec-07 Date Depth of Surface Water (ft) S-SG1 N3C6927C Ground Beginning of growing season End of growing season Sawmill S-SG2 Onsite Reference -1 0 1 2 3 4 5 01-Jan-07 15-Jan-07 29-Jan-07 12-Feb-07 26-Feb-07 12-Mar-07 26-Mar-07 09-Apr-07 23-Apr-07 07-May-07 21-May-07 04-Jun-07 18-Jun-07 02-Jul-07 16-Jul-07 30-Jul-07 13-Aug-07 27-Aug-07 10-Sep-07 24-Sep-07 08-Oct-07 22-Oct-07 05-Nov-07 19-Nov-07 03-Dec-07 17-Dec-07 31-Dec-07 Date Depth of Surface Water (ft) S-SG2 N3C69384 Ground Beginning of growing season End of growing season Data Logger Failure Sawmill S-SG3 1 2 3 4 01-Jan-07 15-Jan-07 29-Jan-07 12-Feb-07 26-Feb-07 12-Mar-07 26-Mar-07 09-Apr-07 23-Apr-07 07-May-07 21-May-07 04-Jun-07 18-Jun-07 02-Jul-07 16-Jul-07 30-Jul-07 13-Aug-07 27-Aug-07 10-Sep-07 24-Sep-07 08-Oct-07 22-Oct-07 05-Nov-07 19-Nov-07 03-Dec-07 17-Dec-07 31-Dec-07 Date Depth of Surface Water (ft) S-SG3 EBDCE63 (in) Ground Beginning of growing season End of growing season Sawmill S-SG4 1 2 3 4 01-Jan-07 15-Jan-07 29-Jan-07 12-Feb-07 26-Feb-07 12-Mar-07 26-Mar-07 09-Apr-07 23-Apr-07 07-May-07 21-May-07 04-Jun-07 18-Jun-07 02-Jul-07 16-Jul-07 30-Jul-07 13-Aug-07 27-Aug-07 10-Sep-07 24-Sep-07 08-Oct-07 22-Oct-07 05-Nov-07 19-Nov-07 03-Dec-07 17-Dec-07 31-Dec-07 Date Depth of Surface Water (ft) S-SG4 EBD016D (in) Ground Beginning of growing season End of growing season Sawmill S-SG5 1 2 3 4 01-Jan-07 15-Jan-07 29-Jan-07 12-Feb-07 26-Feb-07 12-Mar-07 26-Mar-07 09-Apr-07 23-Apr-07 07-May-07 21-May-07 04-Jun-07 18-Jun-07 02-Jul-07 16-Jul-07 30-Jul-07 13-Aug-07 27-Aug-07 10-Sep-07 24-Sep-07 08-Oct-07 22-Oct-07 05-Nov-07 19-Nov-07 03-Dec-07 17-Dec-07 31-Dec-07 Date Depth of Surface Water (ft) S-SG5 EBD06FE (in) Ground Beginning of growing season End of growing season
Object Description
Description
Title | Annual report for... Sawmill mitigation site, Craven County, project no. 8.1170801, TIP no. B-2531WM |
Other Title | Sawmill mitigation site, Craven County |
Date | 2007-12 |
Description | 2007 |
Digital Characteristics-A | 1.06 KB; 33 p. |
Digital Format | application/pdf |
Pres File Name-M | pubs_serial_sawmillmitigationsite2007.pdf |
Pres Local File Path-M | \Preservation_content\StatePubs\pubs_borndigital\images_master\ |
Full Text | ANNUAL REPORT FOR 2007 Sawmill Mitigation Site Craven County TIP No. B-2531WM Prepared By: Natural Environment Unit & Roadside Environmental Unit North Carolina Department of Transportation December 2007 TABLE OF CONTENTS SUMMARY...................................................................................................................... 1 1.0 INTRODUCTION.................................................................................................. 2 1.1 Project Description..................................................................................... 2 1.2 Purpose ..................................................................................................... 2 1.3 Project History ........................................................................................... 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................................................................................... 7 2.4 Conclusions ............................................................................................... 7 3.0 VEGETATION .................................................................................................... 11 3.1 Success Criteria....................................................................................... 11 3.1.1 Bottomland Hardwood Area .......................................................... 11 3.1.2 Marsh Area ................................................................................... 11 3.2 Description of Species ............................................................................. 11 3.3 Results of Vegetation Monitoring……………………………….................. 12 3.4 Conclusions ............................................................................................. 14 3.4.1 Bottomland Hardwood Area .......................................................... 14 3.4.2 Marsh Area ................................................................................... 14 4.0 OVERALL CONCLUSIONS/RECOMMENDATIONS.......................................... 14 LIST OF FIGURES Figure 1. Site Location Map ........................................................................................... 4 Figure 2. Gauge Location Map....................................................................................... 6 Figure 3. 2006 Hydrologic Monitoring Gauge Results .................................................... 9 Figure 4. 30-70 Percentile Graph ................................................................................. 10 LIST OF TABLES Table 1. Hydrologic Monitoring Results.......................................................................... 7 Table 2. Hydrologic Monitoring Results (2003-2007) ..................................................... 7 Table 3. Vegetative Monitoring Statistics (Hardwood Areas) ........................................ 12 Table 4. Vegetative Monitoring Statistics (Marsh Areas).............................................. 13 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 the 2007-year at the Sawmill Mitigation Site. The 2007-year represents the fifth year of hydrology 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 US17 Neuse River Bridge in New Bern. In May 2003, surface water and groundwater gauges were installed to monitor hydrology on the site. Three separate gauge sets, each with one surface and one groundwater gauge, were positioned on the mitigation site. There are also two reference gauge sets that were installed prior to construction. One reference set is located offsite and the other set is 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 hydrologic frequency, duration, and depth consistently within 10% of the hydrology of the reference areas. The 2007-year represents the fifth year of hydrologic monitoring for the Sawmill Mitigation Site. The three groundwater restoration gauges were compared to the two existing reference gauges. Groundwater gauge S-GW5 experienced numerous gauge malfunctions throughout the growing season so no viable conclusions can be taken from its data. Groundwater restoration gauge S-GW3 and S-GW4 indicated that hydrology was not within 10% of reference gauges S-GW1 and S-GW2. It should be noted that it was a below average rainfall year and during such a low rainfall year we would not expect to meet the 10% criteria. The three surface water gauges indicated inundation patterns similar to that of Reference Gauge S-SG2 but showed periods of dryness. Vegetation monitoring in the hardwood area yielded 541 trees per acre. This average is above the minimum success criteria of 320 trees per acre. Supplemental planting of swamp blackgum in January 2004 increased the counts in each plot. For the marsh grass area, the target species and scale values were 100% and 4.5, respectively. NCDOT proposes to discontinue monitoring at the Sawmill Mitigation Site. 2 1.0 INTRODUCTION 1.1 Project Description The Sawmill Mitigation Site serves (entirely) as mitigation for the US17 Neuse River Bridge in New Bern (Figure 1). Situated adjacent to the new bridge alignment, the 4.07- acre site includes both preservation and restoration of brackish tidal marsh as well as tidal cypress-gum swamp. Reference areas, both onsite and offsite, are 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 are based on the National Marine Fisheries Service guidelines. Hydrologic success criteria are based on the approved mitigation plan and require that the site demonstrate hydrologic frequency, duration, and depth consistently within 10% of the hydrology of the reference areas. Included in this report are analyses of hydrologic and vegetation-monitoring results, discussions of local climate conditions throughout the growing season, and site photographs. 3 1.3 Project History 2002 Reference Gauges Installed March 2003 Site Constructed April 2003 Site Planted May 2003 Monitoring Gauges Installed May-November 2003 Hydrologic Monitoring (Year 1) July 2003 Hardwood Vegetation Monitoring (Year 1) July 2003 Marsh Vegetation Monitoring (Year 1) March-November 2004 Hydrologic Monitoring (Year 2) June 2004 Hardwood Vegetation Monitoring (Year 2) June 2004 Marsh Vegetation Monitoring (Year 2) March-November 2005 Hydrologic Monitoring (Year 3) June 2005 Hardwood Vegetation Monitoring (Year 3) June 2005 Marsh Vegetation Monitoring (Year 3) March-November 2006 Hydrologic Monitoring (Year 4) June 2006 Hardwood Vegetation Monitoring (Year 4) June 2006 Marsh Vegetation Monitoring (Year 4) June 2007 Hardwood Vegetation Monitoring (Year 5) June 2007 Marsh Vegetation Monitoring (Year 5) March-November 2007 Hydrologic Monitoring (Year 5) 4 Figure 1. Site Location Map 5 2.0 HYDROLOGY 2.1 Success Criteria The hydrologic success criteria established for the Sawmill Mitigation Site, as stipulated in the approved mitigation plan and subsequent revisions, require that the site demonstrate hydrologic frequency, duration, and depth consistently within 10% of the hydrology of the reference areas. The site-specific criteria vary from current federal guidelines that require a site to be inundated or saturated (within 12” of the surface) by surface or groundwater for a consecutive period amounting to 12.5% of the growing season. The growing season in Craven County begins on March 18 and ends November 14. The dates correspond to a 50% probability that air temperature will drop to 28° after March 18 and before November 141; thus, the growing season is 242 days. Local climate must represent normal conditions for the area. 2.2 Hydrologic Description Wind-driven tides are the primary hydrologic input at the Sawmill Site; therefore, three sets of gauges were installed within the site’s restoration area (Figure 2) in May 2003. Each set includes one surface water gauge and one groundwater-monitoring gauge. There are also two reference gauge sets that were installed prior to construction. One reference set is located offsite and the other set is located directly adjacent to the constructed site, within the preservation area. No rain gauge is located on the site, so rainfall data (supplied by the NC State Climate Office) from an official weather station in New Bern is used to supplement the site data. The surface gauges record surface water levels every three hours, while 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 242-day growing season (March 18 – November 14). Table 1 provides the 2007 hydrologic results; Figure 3 is a graphical representation of these results. Appendix A includes graphs of the data recorded at each groundwater and surface water gauge. Daily rainfall events recorded at the official weather station in New Bern are included on each of the groundwater gauge plots. 1 Soil Conservation Service, Soil Survey of Craven County, North Carolina, 1989. 6 7 Table 1. Hydrologic Monitoring Results Monitoring Gauge Within 10% Actual % Dates of Success S-GW1 (Offsite) (REF) r 100.0 March 18-Nov 14 S-GW2 (Onsite) (REF) r 100.0 March 18-Nov 14 S-GW3 28.0 September 9-Nov 14 S-GW4 45.0 March 18-July 05 S-GW5 36.0 March 18-June 12 Shaded gauges are reference gauges. Specific Gauge Problems: S-GW5: The gauge experienced numerous malfunctions (June 13- September 12). Table 2. Hydrologic Monitoring Results (2003-2007) Monitoring Gauge 2003 Results 2004 Results 2005 Results 2006 Results 2007 Results S-GW1 (Offsite) (REF) 75.8 94.2 60.3 97.9 100.0 S-GW2 (Onsite) (REF) 75.8 100.0 100.0 68.2 100.0 S-GW3 75.8 49.2 71.5 100.0 28.0 S-GW4 75.8 100.0 95.0 100.0 45.0 S-GW5 68.2 50 78.1 100.0 36.0 2.3.2 Climatic Data Figure 4 is a comparison of the 2007 monthly rainfall to the historical precipitation (collected between 1977 and 2007) for New Bern, North Carolina. This comparison gives an indication of how 2007 relates to historical data in terms of climate conditions. The NC State Climate Office provided all local rainfall information. For the 2007-year; April and July experienced above average rainfall. The months of March, May, August, and November recorded below average rainfall, while January, February, June, September, and October recorded average rainfall. Overall, 2007 is considered to be a below average rainfall year. 2.4 Conclusions The 2007-year represents the fifth year of hydrologic monitoring for the Sawmill Mitigation Site. The three groundwater restoration gauges were compared to the two existing reference gauges. Groundwater gauge S-GW5 experienced numerous gauge malfunctions throughout the growing season so no viable conclusions can be taken from its data. Groundwater restoration gauge S-GW3 and S-GW4 indicated that 8 hydrology was not within 10% of reference gauges S-GW1 and S-GW2. The three surface water gauges indicated inundation patterns similar to that of Reference Gauge S-SG2 but show periods of dryness. NCDOT proposes to discontinue monitoring at the Sawmill Mitigation Site. 9 10 Figure 4. 30-70 Percentile Graph Sawmill 30-70 Percentile Graph New Bern, NC 0 1 2 3 4 5 6 7 8 9 Nov 06' Dec 06' Jan 07' Feb 07' Mar 07' Apr 07' May Jun 07' Jul 07' Aug 07' Sep 07' Oct 07' Nov 07' Date Precipitation (in) 2006 Rainfall 2007 Rainfall 30 Percentile 70 Percentile 70 Percentile 30 Percentile Missing Data 11 3.0 VEGETATION: SAWMILL MITIGATION SITE (YEAR 5 MONITORING) 3.1 Success Criteria 3.1.1 Bottomland Hardwood Area The success criteria state that at least 320 stems per acre must survive after the completion of the third growing season and 240 stems per acre after the fifth growing season. If the desired vegetation has not been established, NCDOT will notify the appropriate agencies and will implement corrective measures. 3.1.2 Marsh Grass Area The vegetative success of the marsh portion of the wetland site will be determined in accordance with NMFS Guidelines. Monitoring plots found to be located within the open water channel will not be evaluated, and will not count toward the final count of plots. The vegetation component of the wetland site will be deemed successful if the following criteria are met: 1. At year five, the average of all plots should have a scale value of 5 (>75% vegetative cover) consisting of wetland herbaceous species, not including any invasive species. 2. A minimum of 70% of the plots shall contain the target (planted) species. 3.2 Description of Species The following tree species were planted in the Wetland Restoration Area: Taxodium distichum, Bald cypress Fraxinus pennsylvanica, Green Ash Quercus lyrata, Overcup Oak Nyssa aquatica, Water Tupelo Nyssa sylvatica var. biflora, Swamp Blackgum The following marsh grass species was planted in the Marsh Grass Area: Spartina cynosuroides, Big Cordgrass 12 3.3 Results of Vegetation Monitoring Table 3. Vegetative Monitoring Statistics (Hardwood Areas) Site Notes: Pluchea sp., woolgrass, goldenrod, fennel, wax myrtle, sedge and Juncus sp. Heavy cattails and black willow noted on site. Overcup oaks were noted around the perimeter of plot 1. Plot # Baldcypress Green Ash Overcup Oak Swamp Blackgum Water Tupelo Total (4 year) Total (at planting) Density (Trees/Acre) 1 9 7 4 17 37 48 524 2 2 2 1 0 3 4 2 4 1 5 0 5 5 8 5 4 1 A v e r a g e D e n s ity ( T r e e s /A c r e ) 13 Table 4. Vegetative Monitoring Statistics (Marsh Areas) Plot # Scale Factor Big Cordgrass Frequency Comments 1 4.0 Juncus sp., Black Willow 2 4.0 Juncus sp. 3 5.0 4 5.0 5 5.0 Juncus sp. 6 3.0 Black Willow, Baccharis 7 4.0 Black Willow 8 5.0 Vine, Baccharis 9 4.0 Black Willow 10 4.0 Pennywort, Cattail 11 5.0 12 5.0 13 4.0 Vine 14 5.0 15 5.0 Juncus sp. 16 5.0 Black Willow 17 5.0 Black Willow 18 5.0 19 5.0 20 4.0 Juncus sp., Vine, Pennywort Frequency (Percentage of Plots w/ Desired Species) 100.0% Sum Scale Value 91.0 Total Number of Plots 20 Vegetative Cover (Scale Value) 4.5 Site Notes: The following species were also noted in the monitoring plots. The number of plots the species were found in is following the species in parentheses (i.e. black willow was noted in 6 plots): black willow (6), Juncus sp., (5), cattail (1), pennywort (1), baccharis (2), and vines (2). 14 3.4 Conclusions 3.4.1 Bottomland Hardwood Area There were 2 hardwood vegetation monitoring plots established throughout the 2.4 acre planting area. Swamp blackgum was supplementally planted throughout the site in January 2004, therefore at planting counts increased for each plot. The 2007 vegetation monitoring of the site revealed an average tree density of 541 trees per acre. This average is well above the minimum success criteria of 240 trees per acre. NCDOT proposes to discontinue hardwood vegetation monitoring at the Sawmill Mitigation Site. 3.4.2 Marsh Area • Percent Frequency of Target Species (planted species) 100% Frequency of 70% required. • Vegetative Cover Scale Value 4.5 Scale Value of 5 required for year 5. Of the 4.07 acres of this site, approximately 0.78 acres involved marsh grass planting. There were 20 random plots established throughout the planting area. These plots were located with GPS. Based upon the percent frequency and the scale value, the marsh grass area is on track for the fifth year of monitoring. NCDOT proposes to discontinue marsh grass monitoring at the Sawmill Mitigation Site. 4.0 OVERALL CONCLUSIONS/RECOMMENDATIONS The 2007-year represents the fifth year of hydrologic monitoring for the Sawmill Mitigation Site. The three groundwater restoration gauges were compared to the two existing reference gauges. Groundwater gauge S-GW5 experienced numerous gauge malfunctions throughout the growing season so no viable conclusions can be taken from its data. Groundwater restoration gauge S-GW3 and S-GW4 indicated that hydrology was not within 10% of reference gauges S-GW1 and S-GW2. The three surface water gauges indicated inundation patterns similar to that of Reference Gauge S-SG2 but show periods of dryness. Vegetation monitoring in the hardwood area yielded 541 trees per acre. This average is above the minimum success criteria of 320 trees per acre. Supplemental planting of swamp blackgum in January 2004 increased the counts in each plot. For the marsh grass area, the target species and scale values were 100% and 4.5, respectively. NCDOT proposes to discontinue all monitoring in 2008. APPENDIX A GAUGE DATA GRAPHS APPENDIX B PHOTO AND VEGETATION PLOT LOCATIONS, SITE PHOTOS Sawmill Photo 1 Photo 2 Photo 3 Photo 4 Photo 5 Photo 6 June 2007 APPENDIX A GAUGE DATA GRAPHS Sawmill S-GW1 Offsite Reference -20 -15 -10 -5 0 5 10 15 20 01-Jan-07 15-Jan-07 29-Jan-07 12-Feb-07 26-Feb-07 12-Mar-07 26-Mar-07 09-Apr-07 23-Apr-07 07-May-07 21-May-07 04-Jun-07 18-Jun-07 02-Jul-07 16-Jul-07 30-Jul-07 13-Aug-07 27-Aug-07 10-Sep-07 24-Sep-07 08-Oct-07 22-Oct-07 05-Nov-07 19-Nov-07 03-Dec-07 17-Dec-07 31-Dec-07 Date Groundwater (in) 0 0.5 1 1.5 2 2.5 3 3.5 4 Precipitation (in) Rainfall S-GW1 9BEB426 (in) Required Depth Beginning of growing season End of growing season 242 Days Sawmill S-GW2 Onsite Reference -20 -15 -10 -5 0 5 10 15 20 01-Jan-07 15-Jan-07 29-Jan-07 12-Feb-07 26-Feb-07 12-Mar-07 26-Mar-07 09-Apr-07 23-Apr-07 07-May-07 21-May-07 04-Jun-07 18-Jun-07 02-Jul-07 16-Jul-07 30-Jul-07 13-Aug-07 27-Aug-07 10-Sep-07 24-Sep-07 08-Oct-07 22-Oct-07 05-Nov-07 19-Nov-07 03-Dec-07 17-Dec-07 31-Dec-07 Date Groundwater (in) 0 0.5 1 1.5 2 2.5 3 3.5 4 Precipitation (in) Rainfall S-GW2 A28BC2A (in) Required Depth Beginning of growing season End of growing season 242 Days Sawmill S-GW3 -30 -25 -20 -15 -10 -5 0 5 10 15 20 01-Jan-07 15-Jan-07 29-Jan-07 12-Feb-07 26-Feb-07 12-Mar-07 26-Mar-07 09-Apr-07 23-Apr-07 07-May-07 21-May-07 04-Jun-07 18-Jun-07 02-Jul-07 16-Jul-07 30-Jul-07 13-Aug-07 27-Aug-07 10-Sep-07 24-Sep-07 08-Oct-07 22-Oct-07 05-Nov-07 19-Nov-07 03-Dec-07 17-Dec-07 31-Dec-07 Date Groundwater (in) 0 0.5 1 1.5 2 2.5 3 3.5 4 Precipitation (in) Rainfall S-GW3 9BEBFF0 (in) Required Depth Beginning of growing season End of growing season 43 Days 24 Days 17 Days 67 Days 30 Days Sawmill S-GW4 -20 -15 -10 -5 0 5 10 15 20 01-Jan-07 15-Jan-07 29-Jan-07 12-Feb-07 26-Feb-07 12-Mar-07 26-Mar-07 09-Apr-07 23-Apr-07 07-May-07 21-May-07 04-Jun-07 18-Jun-07 02-Jul-07 16-Jul-07 30-Jul-07 13-Aug-07 27-Aug-07 10-Sep-07 24-Sep-07 08-Oct-07 22-Oct-07 05-Nov-07 19-Nov-07 03-Dec-07 17-Dec-07 31-Dec-07 Date Groundwater (in) 0 0.5 1 1.5 2 2.5 3 3.5 4 Precipitation (in) Rainfall S-GW4 9DE53A2 (in) Required Depth Beginning of growing season End of growing season 110 Days 41 Days 80 Days Sawmill S-GW5 -20 -15 -10 -5 0 5 10 15 20 01-Jan-07 15-Jan-07 29-Jan-07 12-Feb-07 26-Feb-07 12-Mar-07 26-Mar-07 09-Apr-07 23-Apr-07 07-May-07 21-May-07 04-Jun-07 18-Jun-07 02-Jul-07 16-Jul-07 30-Jul-07 13-Aug-07 27-Aug-07 10-Sep-07 24-Sep-07 08-Oct-07 22-Oct-07 05-Nov-07 19-Nov-07 03-Dec-07 17-Dec-07 31-Dec-07 Date Groundwater (in) 0 0.5 1 1.5 2 2.5 3 3.5 4 Precipitation (in) Rainfall S-GW5 9DE5829 (9DE6718) (in) Required Depth Data Logger Failure Beginning of growing season End of growing season 87 Days 63 Days Sawmill S-SG1 Offsite Reference -1 0 1 2 3 4 5 01-Jan-07 15-Jan-07 29-Jan-07 12-Feb-07 26-Feb-07 12-Mar-07 26-Mar-07 09-Apr-07 23-Apr-07 07-May-07 21-May-07 04-Jun-07 18-Jun-07 02-Jul-07 16-Jul-07 30-Jul-07 13-Aug-07 27-Aug-07 10-Sep-07 24-Sep-07 08-Oct-07 22-Oct-07 05-Nov-07 19-Nov-07 03-Dec-07 17-Dec-07 31-Dec-07 Date Depth of Surface Water (ft) S-SG1 N3C6927C Ground Beginning of growing season End of growing season Sawmill S-SG2 Onsite Reference -1 0 1 2 3 4 5 01-Jan-07 15-Jan-07 29-Jan-07 12-Feb-07 26-Feb-07 12-Mar-07 26-Mar-07 09-Apr-07 23-Apr-07 07-May-07 21-May-07 04-Jun-07 18-Jun-07 02-Jul-07 16-Jul-07 30-Jul-07 13-Aug-07 27-Aug-07 10-Sep-07 24-Sep-07 08-Oct-07 22-Oct-07 05-Nov-07 19-Nov-07 03-Dec-07 17-Dec-07 31-Dec-07 Date Depth of Surface Water (ft) S-SG2 N3C69384 Ground Beginning of growing season End of growing season Data Logger Failure Sawmill S-SG3 1 2 3 4 01-Jan-07 15-Jan-07 29-Jan-07 12-Feb-07 26-Feb-07 12-Mar-07 26-Mar-07 09-Apr-07 23-Apr-07 07-May-07 21-May-07 04-Jun-07 18-Jun-07 02-Jul-07 16-Jul-07 30-Jul-07 13-Aug-07 27-Aug-07 10-Sep-07 24-Sep-07 08-Oct-07 22-Oct-07 05-Nov-07 19-Nov-07 03-Dec-07 17-Dec-07 31-Dec-07 Date Depth of Surface Water (ft) S-SG3 EBDCE63 (in) Ground Beginning of growing season End of growing season Sawmill S-SG4 1 2 3 4 01-Jan-07 15-Jan-07 29-Jan-07 12-Feb-07 26-Feb-07 12-Mar-07 26-Mar-07 09-Apr-07 23-Apr-07 07-May-07 21-May-07 04-Jun-07 18-Jun-07 02-Jul-07 16-Jul-07 30-Jul-07 13-Aug-07 27-Aug-07 10-Sep-07 24-Sep-07 08-Oct-07 22-Oct-07 05-Nov-07 19-Nov-07 03-Dec-07 17-Dec-07 31-Dec-07 Date Depth of Surface Water (ft) S-SG4 EBD016D (in) Ground Beginning of growing season End of growing season Sawmill S-SG5 1 2 3 4 01-Jan-07 15-Jan-07 29-Jan-07 12-Feb-07 26-Feb-07 12-Mar-07 26-Mar-07 09-Apr-07 23-Apr-07 07-May-07 21-May-07 04-Jun-07 18-Jun-07 02-Jul-07 16-Jul-07 30-Jul-07 13-Aug-07 27-Aug-07 10-Sep-07 24-Sep-07 08-Oct-07 22-Oct-07 05-Nov-07 19-Nov-07 03-Dec-07 17-Dec-07 31-Dec-07 Date Depth of Surface Water (ft) S-SG5 EBD06FE (in) Ground Beginning of growing season End of growing season |
OCLC number | 785387613 |