Numerical Groundwater Flow Modeling of a Northern Appalachian Coal Basin Bedrock Valley Exhibiting Stress-Relief Fractures

Wednesday, June 19, 2013: 11:05 a.m.
Andrew Ashton , Industrial Client Service Area, Sanborn, Head and Associates, Inc., Concord, NH
Charles Crocetti , Sanborn, Head & Associates, Inc., Concord, NH
John Massey-Norton , American Electric Power, Columbus, OH
Steven Orenchuk , American Electric Power, Columbus, OH

Permitting of fly ash impoundments requires a solid understanding of the groundwater system, both the physical properties governing flow and the natural variability of the groundwater geochemistry. At the site in this case study, sandstones of the Monongahela, Conemaugh, and Allegheny formations form the major water-bearing aquifers with thick shale sequences forming intervening aquitards. Borehole geophysics conducted at the site indicates that fracture flow plays a dominant role in the movement of groundwater. The fly ash ponds in this study are located in a high-relief, upland setting and stress-relief fracturing is expected to play an important role near the valley sides. Groundwater monitoring conducted at the site during the last 28 years, including stable isotope analysis, has provided considerable data on the flow system. As part of a recent permit application to increase the capacity of the existing fly ash pond, we developed a 20-square-mile, 10-layer, steady-state groundwater flow model using MODFLOW-NWT, a stand-alone version of MODFLOW 2005. Pre-processing of the model, including development of the geological conceptual model, was conducted in GIS to increase the efficiency of the modeling process. The challenge at the site is to distinguish constituents naturally present in groundwater and those potentially due to leaching from the fly ash reservoirs. Impacts from extensive coal mining and petroleum exploration over the last 100 years further complicate the interpretation of groundwater geochemistry. Particle tracks were generated from the numeric modeling simulations and the results helped to verify the groundwater flow-paths as indicated by groundwater contours and geochemical data. Ultimately the model was a key component in the permit, allowing an understanding of future conditions and guiding development of future monitoring plans.

Andrew Ashton, Industrial Client Service Area, Sanborn, Head and Associates, Inc., Concord, NH
Andrew Ashton is a Project Manager at Sanborn, Head & Associates with more than nine years of experience in environmental consulting. He is primarily focused on investigation and remediation of chlorinated volatile organic compounds and hydrocarbon contamination at industrial sites located in the United States, Europe, and South America. Prior to working for Sanborn Head, Ashton worked as a hydrogeologist in the UK with a focus on environmental assessment for clients in the mining and building industries. He earned a B.Sc. in exploration geophysics from University College London, and an M.Sc. from Imperial College London in hydrology for environmental management.

Charles Crocetti, Sanborn, Head & Associates, Inc., Concord, NH
Charles Crocetti is a Senior Vice President and cofounder of Sanborn, Head & Associates, with over 25 years experience in hydrogeological, environmental, and remedial projects, in over 20 states and internationally, including 12 Superfund sites. Chip's particular expertise is the application of geochemistry to hydrogeological and environmental issues. Recent interests include: assessment and control of impacts to groundwater due to blasting; emerging contaminant 1,4-dioxane; and geologic and geochemical influences on the success of geothermal/ground source heat pump systems. Crocetti earned a B.A. from Dartmouth College in earth sciences, and an M.S. and doctorate in geological sciences from Harvard University.

John Massey-Norton, American Electric Power, Columbus, OH
John Massey-Norton has been employed at AEP for 30 years and is responsible for investigating groundwater resources at power plants and ash disposal sites. He has managed engineering studies related to erosion and sedimentation that supported the relicensing of major hydroelectric impoundments. He has participated in power plant siting studies and deep-well injection of carbon dioxide. He has also worked with Ohio State University using coal combustion byproducts in mine reclamation studies. He holds a B.S. in geology from Western Illinois University and an M.S. in geology from Ohio University. His first professional employment was with the NGWA in 1977.

Steven Orenchuk, American Electric Power, Columbus, OH
Steven Orenchuk has been employed at AEP for five years and is responsible for groundwater monitoring, investigations, and reporting associated with disposal facilities (wet and dry) for coal combustion byproducts (CCBS). Other areas of responsibility include permitting support for CCB landfills and impoundments including the development of groundwater monitoring programs. He holds a B.S. degree in civil engineering with a concentration in environmental engineering from the Ohio State University. His first professional employment was with the Ohio Environmental Protection Agency in 2006.