(N. C. CEIP Report No. 41) HYDROLOG IC AND WATER QUALITY IMPACTS OF PEAT MINING IN NORTH CAROLINA -L n Jd- J. D. R. W. R. G. Gregory, Skaggs, J1 ~roadheady~ R. H. ~ulbreath," J. R. Bailey," and T. L. Foutzda' 9: Department of Forestry Department of Biological and Agricultural EngineeringJ,* North Carolina State University Raleigh, NC 27695 The work upon which this publication is based was supported by (1) a Coastal Energy Impact Program grant provided by the North Carolina Coastal Management Program through funds authorized by the Coastal Zone Management Act of 1972, as amended, and administered by the Off ice of Coastal Management, National Oceanic and Atmospheric Administration; and (2) by the North Carolina Agricultural Research Service in cooperation with First Colony Farms, Inc. and Peat Methanol Associates. Project administration was provided by the Water Resources Research ~nstituteof The University of North Carolina. NOAA Grants No. NA-79-AA-D-CZ097 and NA-80-AA-D-CZ149 WRRI Project Nos. 5007Wand 50071 August 1984 ACKNOWLEDGMENTS Major support for this research was provided by The National Oceanic and Atmospheric Administration through The Coastal Energy Impact Program and the North Carolina Office of Coastal Management. The support and assistance of James F. Smith, Coordinator North Carolina Coastal Energy Impact Program is gratefully acknowledged. The study was conducted at First Colony Farms, Creswell, North Carolina. We thank Andy Allen and Steve Barnes whose staff installed the flashboard riser structures, constructed and maintained the stilling ponds and provided other assistance in the field work. Additional support was provided by The North Carolina Agricultural Research Service in the form of faculty time. We thank Dr. James M. Stewart, Associate Director and Linda Kiger, Administrative Manager of the Water Resources Research Institute, for their assistance in administering the project. The dedication of Beth Haines in assisting with field work and laboratory analyses is gratefully acknowledged. Thanks are due to Judy Graybeal, Judy Parker, Lorene Nicdao, Teresa Berry, and Thelma Utley for the many hours spent at the word processor. Clay Cockrell provided -invaluable assistance in developing data management procedures. We thank Dr. Michael Amein for allowing us to use his Flood Routing Model and for advice in its operation and modification. DISCLAIMER STATEMENT Contents of this publication do not necessarily reflect the views and policies of the Water Resources Research Institute nor does mention of trade names or commercial products constitute their endorsement or recommendation for use by the Institute or the State of North Carolina. iii ABSTRACT The surface and subsurface hydrologic impacts of peat mining were studied at a pocosin site in the lower Coastal Plain of Northeastern North Carolina. Runoff and water quality data were collected for discharge from field ditches draining sites being actively mined and sites with natural vegetation, A water management model (DRAINMOD) was adapted to simulate surface hydrology. The finite element method was used to evaluate the effects of peat mining on vertical seepage to a deep aquifer and lateral seepage from a nearby lake, Volume, duration, and peak flow of storm discharge from field ditches was greater from the mining sites than from those having natural vegetation. Baseflow between storm events was greater from vegetated sites than from the mined sites. Reduced evapotranspiration, reduced infiltration capacity and grading and sloping of the surface are most likely responsible for those differences. Relatively high concentrations of organic sediment in field ditch outflows resulted from the highly erodible state of the mined surface and the field ditch channels. However, much of the sediment load settled in the weir stilling ponds and concentra- tions decreased downstream in collector and main canels due to setting and dilution. Concentrations of nitrogen and phosphorus varied little among sampling sites but were considerably higher than those reported in outflow from similar sites with natural vegetation in several other studies. Mining appeared to have no significant impact on concentrations of K, Car Mg, and C1 in outflows. The water management model, DRAINMOD, was coupled with a numerical flood routing model and utilized to predict the long- term hydrologic effects of mining the peat bogs and reclaiming them to agriculture, During actual mining, the volume of water entering the canals will be increased by an annual average of about 29% over that from a well-vegetated area, Simulated compar isons of pre- and pos t-mining hydrology revealed that post- mining hydrology of land under cultivation will not be much different from pre-mining hydrology except that improved water management can be exercised Data from drill holes to a depth of 17,8m at 22 locations at the peat mining site were used to describe the underlying sedi- ments. Utilizing the finite element method, the deep seepage rate to the Castle Hayne aquifer was estimated to be 0.039 cm/yr and was not altered by mining. Mining had no effect on total seepage out of Lake Phelps. TABLE OF CONTENTS Page ACKNOWLEDGMENTS . iii ABSTRACT. v TABLE CONTENTS vii LISTOFFIGURES ...................... xi LISTOFTABLES... .........*.... .... xix SUMMARY AND CONCLUSIONS . xxi RECOMMENDATIONS 0. xxv I. INTRODUCTION . , . , . 1 LITERATURE CITED . 3 I I. PEAT RESOURCES AND THE POTENTIAL HYDROLOGIC IMPACTS OF PEAT MINING AND RECLAMATION ACTIVITIES - A LITERA- TURE REVIEW . 4 WHAT PEAT IS AND IS NOT . 4 TYPES OFPEATDEPOSITS . 5 NORTH CAROLINA PEAT DEPOSITS . 5 WORLD PEAT RESOURCES AND USE . 7 PEAT MINING FOR ENERGY PRODUCTION . , . 8 HYDROLOGY OF NATURAL AND ALTERED PEATLAND . 9 Water Movement in Natural Peatlands . Water Quality in Natural Peatlands . Changes in Water Movement with Artificial Drainage. Changes in Water Movement with Land Clearing. Changes in Water Movement with Artificial Drainage and Land Clearing . Changes in Water Movement with Peat ~ining . Changes in Water Movement with Reclamation . Changes in Water Quality with Artificial Drainage . Change in Water Quality with Artificial Drainage and Land Clearing . Changes in Water Quality with Peat Mining . Changes in Water Quality with Agricultural Reclama- tion....................... Changes in Water Quality with Forest Reclamation. LITERATURECITED . 23 vii 111. EFFECTS OF PEAT MINING ON RUNOFF AND WATER QUALTIY . INTRODUCTION. .................... PROCEDURES ...................... Site Description .... ....... ....... Sampling Site Selection ............... Hydrologic Measurements ............... Water Quality Measurements. ............. RESULTS AND DISCUSSION. ............... Runoff ....................... WaterQuality .................... SUMMARY AND CONCLUSIONS ............... LITERATURE CITED ................... IV. COMPUTER MODELS FOR ANALYSIS OF HYDROLOGIC EFFECTS OF PEATMINING... ................... INTRODUCTION ..................... MODEL DEVELOPMENT .................. Field Hydrology Model ................ Flood Routing Model. ................. MODELTESTING .................... Introduction ..................... Input data.. .................... Results and Discussion ................ Conclusions ...................am ANALYSIS OF HYDROLOGIC EFFECTS OF PEAT MINING ..... Comparison of Pre-Mining and Post-Mining Hydrology . Hydrologic Effects of Alternative Post-Mining Drainage Systems. ...................... Hydrologic Effects of Alternative Post-Mining Crop Rotations ...................... Analysis of Hydrologic Effects During the Mining Process. ...................... Analysis of Hydrologic Effects of Mining Strategy . RECOMMENDATIONS .................... SUMMARY. ....................... LITERATURE CITED. ................... viii V . EFFECTS OF PEAT MINING ON GROUNDWATER PROCESSES .... 175 INTRODUCTION. ..0............-..... 175 PHYSICAL PROPERTIES OF MINERAL SEDIMENTS ....... 175 Introduction ..................... 175 Procedures ...................... 176 Results and Conclusions ............... 178 ANALYSIS OF GROUNDWATER MOVEMENT ........... 193 Introduction ..................... 193 Procedures ...................... 193 Results and Discussion ................ 196 SUMMARYANDCONCLUSIONS ................ 212 LITERATURE CITED ................... 214 LIST OF FIGURES Page Figure 1. General location of permitted peat mining area . Figure 2. Permitted peat mining area . Figure 3A. Natural vegetation on the mine site . 3B. White cedar logs removed from the peat during canal construction. Figure 4. Drainage system characteristics. .. Figure 5. Drainage flow pattern in the peat mine area. Figure 6A. Field ditch on site with natural vegetation. B. Field ditch on site prepared for peat harvesting . Figure 7. Location of pilot mining area and sampling sites . ;. Figure 8. Location of sampling sites for runoff and water quality in field ditches on the pilot mining area . Figure 9. Portion of permitted mine area burned by wildfire in 1981. Figure 10. Aftermath of 1981 wildfire. Figure 11A. ~nstallationof weir in flashboard riser. 11~.Completed weir installation with trash screen. Figure 12A. Complete runoff measurement installation. B. Silt screen installed in field ditch. Figure 13. Organic sediment and wood accumulated in field ditch and stilling pond, (A) without silt screen (B) with silt screen. Figure 14. Weir installation on DeHoog Canal . Figure 15. Runoff from field ditches draining cleared and vegetated sites (4 ha in size) for a storm in December,