EIACP (PC-RP) on Environmental Problems of Mining

1999 International Ash Utilization Symposium, Center for Applied Energy Research, University of Kentucky, Paper #31. Copyright is held by the Authors.

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Evaluation of Water Quality Conditions Associated with the Use of Coal Combustion Products for Highway Embankments

Matthew W. Erbe¹, Robert W. Keating¹, and William K. Hodges, Ph.D.²

¹ERM, Annapolis, Maryland 21401;

²Maryland Department of Natural Resources, Power Plant Research Program, Annapolis, Maryland 21401

Potential users, regulators and the public have expressed uncertainty regarding the potential for coal combustion products (CCPs) used as structural fill in highway embankments to degrade ground water quality. The Maryland Department of Natural Resources Power Plant Research Program (PPRP) is conducting field studies at two Maryland sites in which CCPs were used to construct highway embankments to assess ground water quality impacts and promote the beneficial use of CCPs generated in Maryland. One study is being conducted at the Routes 213/301 overpass, and the second study is being conducted at the I-695 overpasses. The purpose of the studies is to determine the potential for leachate to form within the pore water in the CCP embankments, and evaluate whether the leachate is degrading ground water quality.

The study at the I-695 overpasses is in the work plan development phase. The study at the Routes 213/301 overpass was initiated in March 1999 and is substantially completed. Lysimeters, monitoring wells and soil moisture probes were installed in and through the CCP fill on the shoulder of Route 213. A tipping bucket range gauge was installed to monitor precipitation at the study site. Samples were collected to provide information regarding the material’s physical and chemical properties, and were used to assess those factors that affect the attenuation of constituents. Pore and ground water samples collected at the site were analyzed for dissolved trace elements, major cations and anions, and alkalinity. Temperature, pH, and specific conductance were measured in the field.

Water quality results indicate elevated concentrations of several trace elements (arsenic and manganese) and major ions (calcium, magnesium, chloride, and sulfate) were found in fly ash pore water, indicating that leachate is forming within the fly ash fill. However, the data also indicate that these constituents are being attenuated in underlying soils and ground water beneath the embankments. The water quality data collected to date indicate that the use of fly ash for highway embankments can adequately protect ground water quality.

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