Final Report Methodology to Assess Soil, Hydrologic, and Site Parameters that Affect Wetland Restoration Prepared By M.J. Vepraskas, J.G. White, R.L. Huffman, G.P. Fernandez, R.W. Skaggs, B. Lees, C.W. Zanner, J.M. Stucky, J.D.Gregory, W.S. Broome, J.M. Ewing, R.P. Szuch, S. Luginbhul, and G.S. Kreiser North Carolina State University Department Soil Science, Botany, and Agricultural Engineering, and Forestry Box 7619 Raleigh, NC 27695-7619 June 2005 Technical Documentation Page 1. Report No. 2. Government Accession No. 3. Recipient’s Catalog No. FHWA/NC/2003-06 4. Title and Subtitle 5. Report Date Methodology to Assess Soil, Hydrologic, and Site Parameters that June 2005 Affect Wetland Restoration 6. Performing Organization Code 7. Author(s) 8. Performing Organization Report No. M. J. Vepraskas et al. 9. Performing Organization Name and Address 10. Work Unit No. (TRAIS) North Carolina State University Dep. of Soil Science Box 7619 Raleigh, NC 27695-7619 11. Contract or Grant No. 12. Sponsoring Agency Name and Address 13. Type of Report and Period Covered US Department of Transportation Final Report Research and Special Programs Administration July 1, 2000 to June 30, 2003 400 7th Street, SW Washington, DC 20590-0001 Sponsoring Agency Code 2001-09 13. Supplementary Notes: Supported by a grant from the US Department of Transportation and the North Carolina Department of Transportation through the Center for Transportation and the Environment, NC State University. 16. Abstract Juniper Bay is a 750 acre Carolina Bay that was purchased by the NC Department of Transportation for wetland restoration. This report summarizes the current condition of the site and reviews its history, geology, hydrology, soils, and also provides data on the target or reference areas that the Bay will be restored to. Juniper Bay was converted to agriculture in the 1970’s when its timber was removed and the area was ditched, drained, and fertilized for row crop production. The fertilization increased the levels of plant nutrients in the upper 12 in. of soil to levels approximately five times greater than those found in the original soil. Despite the fertile nature of the soils, nutrient levels in drainage waters were low. A water budget indicated that ground water could comprise between 10 and 35% of the total water input to the Bay. A more precise estimate will require better estimates of evapotranspiration. Evaluation of restoration methodologies indicated that in order for the site to meet the 12.5% criterion the ditches would have to be plugged, field crowns removed, and surface roughness increased. This scenario was developed assuming that ground water inflow did not have a significant impact on water table levels. Examination of vegetation soils in natural bays indicated that pond pine woodland is the most appropriate target community for the existing soils in Juniper Bay. Subsidence of the organic soil surface by up to 2 ft. precludes high pocosin or bay forest plant communities for Juniper Bay. 17. Key Words 18. Distribution Statement Natural resources, ecosystems, environmental No restrictions quality, land use 19. Security Classif. (of this report) 20. Security Classif. (of this page) 21. No. of Pages 22. Price Unclassified Unclassified 312 Form DOT F 1700.7 (8-72) Reproduction of completed page authorized DISCLAIMER The contents of this report reflect the views of the authors, who are responsible for the facts and accuracy of the data presented herein. This document is disseminated under the sponsorship of the U.S. Department of Transportation and North Carolina Department of Transportation in the interest of information exchange. This report don not constitute a standard, specification, or regulation. The US Government assumes no liability for the contents or use thereof. ACKNOWLEGEMENTS Support was provided by the Center for Transportation and the Environment in cooperation with the U.S. Department of Transportation and the North Carolina Department of Transportation through the Institute for Transportation Research and Education, North Carolina State University. We would like to thank the Technical Advisory Committee for assisting in this research. The committee members include: James Hauser (chair), John Fisher, Matt Flint, Randy Griffin, Elizabeth Lusk, David Henderson, Lielani Paugh, Rodger Rochelle, Max Tate, Moy Biswas, Gordon Cashin, and Derry Schmidt. From NC State University, this project was conducted by a number of graduate students and technicians. Alex Adams led the support effort for 3 years and without his leadership and service this project would not have been completed. James Cox and Bryan Roberts were also essential in supporting numerous field efforts. The USDA also assisted the research. James Doolittle led the ground-penetrating radar activities for 3 years, and was recently helped by Wesley Tuttle. Dr. Douglas Wysocki is working on the geomorphology of Juniper Bay. Frank Rowe was invaluable in operating a drilling truck that collected the sediment cores. iii SUMMARY Juniper Bay is a 750 acre Carolina Bay that was purchased by the NC Department of Transportation for wetland restoration. This report summarizes the current condition of the site and reviews its history, geology, hydrology, soils, and also provides data on the target or reference areas that the Bay will be restored to. Juniper Bay lies on the Middle Atlantic Coastal Plain. Below its surface are alternating layers of sands and clays to a depth of over 50 ft. A clay layer at approximately 20 ft. lies beneath the entire Bay. In its natural state, the Bay probably supported plant communities that are described as pond pine woodland, bay forest, and high pocosin. Juniper Bay was converted to agriculture in the 1970’s when its timber was removed and the area was ditched, drained, and fertilized for row crop production. The fertilization increased the levels of plant nutrients in the upper 12 in. of soil to levels approximately five times greater than those found in the original soil. Despite the fertile nature of the soils, nutrient levels in drainage waters were low. Organic soils cover approximately one-half the Bay. As a result of land clearing operations and drainage, the surface of the organic soil has subsided approximately 24 in. over the previous 30 yr. The shallowest clay layer varied in depth from 20 in. to 10 ft. across the site and had an average depth of 60 in. This layer is probably not a single, continuous layer, but consists of overlapping clay layers of varying thicknesses. In the southeast corner of the Bay, no clay layer was detected in an area 8 acres in size to a depth of 15 ft. This could be a point of leakage or groundwater inflow. Measurements of hydraulic gradients across the Bay showed that ground water was entering the Bay to the east and west. It was leaving the Bay to the north and south. Most groundwater movement appeared to occur between a depth of 10 to 20 ft. This was generally below the depth of the lateral ditches. However, it did appear some ground water was moving toward the surface of the Bay in some sections and may be entering ditches. A water budget indicated that ground water could comprise between 10 and 35% of the total water input to the Bay. A more precise estimate will require better estimates of evapotranspiration. Long-term simulations using the hydrologic model DRAINMOD indicated that under current conditions the six sites monitored within Juniper Bay do not satisfy the hydrologic criterion for wetland if the duration is based on 12.5% of the growing season. Evaluation of restoration methodologies indicated that in order for the site to meet the 12.5% criterion the ditches would have to be plugged, field crowns removed, and surface roughness increased. This scenario was developed assuming that ground water inflow did not have a significant impact on water table levels. iv TABLE OF CONTENTS Technical Report Documentation........................................................................................ii Disclaimer and Acknowledgments .....................................................................................iii Summary...............................................................................................................................iv Chapter 1: Introduction........................................................................................................1 Chapter 2: Surficial Geology of Southern North Carolina................................................................................................................................13 Chapter 3: Historical Records of Agricultural Practices that Affected Hydrology and Soils at Juniper Bay .........................................................38 Chapter 4: Vegetation of Three Reference Carolina Bays in Relation to Soils and Hydrology...........................................................................56 Chapter 5: Chemical Soil Properties of Juniper Bay After 15, 20, and 30 Years of Drainage and Agricultural Production.....................................92 Chapter 6: Physical and Morphological Characteristics of a Carolina Bay Wetland Soils After 15, 20, and 30 Years of Drainage and Agricultural Production............................................................126 Chapter 7: Estimating Primary and Secondary Subsidence in an Organic Soil 15, 20, and 30 Years After Drainage........................................................................................................163 Chapter 8: Nutrient Analysis of Drainage