Date of Award


Document Type


Degree Name

Master of Science (MS)



First Advisor

P.J. Gerla


Coal Creek Station is a two-unit 1100 megawatt electrical power plant located in southern McLean county, North Dakota. Annually, 5 million tons (4.5 million metric tons) of lignite are burned at the plant producing 550,000 tons (500,000 metric tons) of fly ash. Approximately 80,000 tons (72,624 metric tons) of ash are sold as a cement replacement, while the remainder is disposed of in lined evaporation ponds. The present study investigates the environmental consequences of ash utilization as an alternative to disposal, The Electric Power Research Institute (EPRI) provided funding for this investigation which involves the installation of 5,288 cu yds (4,043 m3) of concrete in roadways at ccs. The concrete contains a 70% replacement of Portland cement with fly ash. The purpose of this study was to determine whether or not use of fly ash in concrete releases any environmentally deleterious substances to soil or ground water.

Stratigraphy at the site consists of a variable unit of fill material underlain by Paleocene bedrock of the Sentinel Butte Formation. The fill unit was created by construction projects during the past 10 years. Fill materials are more permeable than bedrock, consequently the occurrence of fill influences recharge rates and ground water flow patterns.

A comprehensive water monitoring network encompassing surface water, unsaturated zone water, and saturated zone water was designed for the site. Surface water quality was documented using a runoff collector and precipitation collector. soil moisture and ground water occurrence and quality were monitored using pressure-vacuum lysimeters and monitoring wells.

Two geologically distinct sites were instrumented, one representing a recharge zone {monitoring nest 2) and the other a zone of little recharge (monitoring nest 1). Each monitoring nest contains J pressure vacuum lysimeters at depths of 5, 10, and 15 feet (1.5, J.o, and 4.5 m) and 1 monitoring well. Both monitoring nests were downgradient of fly ash concrete installations. Background water quality data were provided by preconstruction samples and two monitoring wells upgradient from the site.

To date, data suggest that there has been no degradation in water quality attributable to leaching from the concrete. Data obtained from monitoring nest 2 indicate that in recharge zones the composition of water in the saturated zone is largely determined within the unsaturated zone. The creation of localized recharge zones may mobilize certain constituents of the unsaturated zone causing a degradation of water quality in the saturated zone. In settings characterized by low recharge, much of the mineralization available to the system remains in the unsaturated zone and the composition of the unsaturated and saturated zone remains chemically distinct.

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