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Title: The effects of fly ash and flue-gas desulfurization wastes on groundwater quality in a reclaimed lignite strip mine disposal site: Volume I: Final report

Technical Report ·
OSTI ID:6909017

Coal conversion wastes were generated at a lignite-fired, steam-electric power station near Center, North Dakota, and were buried in unsaturated and saturated settings within the nearby strip mine, typical of settings used by the industry. The field study of the effects of fly ash and flue gas desulfurization (FGD) wasts on groundwater quality in a reclaimed lignite strip mine disposal site ran for eight years beginning in 1978. Chemical analyses for major cations and anions, As, Se, Mo, Ba, Pb, Cr, Hg, and other constituents were performed on groundwater samples from selected settings and strata. Fly ash and the FGD waste initially generate highly mineralized leachates from entrained water. Fly ash generates an initially high ph leachate. FGD wastes produce normal (6-9) pH values. Leachate pH is quickly buffered to the six to nine range within the sediments. Arsenic and selenium are simultaneously attenuated to acceptable levels. Lead, cadmium, and barium are maintained at low levels by sulfate and carbonate precipitation reactions. Molybdenum remains mobile in this hydrogeochemical setting. The cation exchange capacity of Na-montmorillonite clays may account for decreases in calcium and increases in sodium concentration levels with depth. Sulfate concentration levels decline with depth where bacterially-induced sulfate reduction apparentlay occurs. Pozzolanic activity within the fly ash deposits, in both saturated and unsaturated settings, apparently reduces the mobility of all constituents. A disposal site, well above the reestablished groundwater table, protected from recharge, is considered the best setting for disposal of these wastes because very little leachates forms. Lined disposal sites are therefore unnecessary to control regulated trace elements, but would be necessary to contain sodium, calcium, sulfate, and molybdenum migration in saturated settings. 30 refs., 256 figs., 6 tabs.

Research Organization:
North Dakota Univ., Grand Forks (USA). North Dakota Mining and Mineral Resources Research Inst.
DOE Contract Number:
AK18-80FC10120; AT21-80FC10230; AT18-83FC10612
OSTI ID:
6909017
Report Number(s):
DOE/FC/10120-2550-Vol.1; ON: DE88001048
Resource Relation:
Other Information: Portions of this document are illegible in microfiche products
Country of Publication:
United States
Language:
English