Field evaluation of the comanagement of utility low-volume wastes with high-volume coal combustion by-products: SX site. Final report

This report describes and summarizes the results of a field evaluation of the comanagement of utility low-volume wastes with high-volume coal combustion by-products at a 1,008-megawatt generating station in the midwestern US. The investigation at this plant, referred to as the SX site, consisted of six elements: identification of waste types and waste handling practices; sampling of individual and comanaged waste streams, geochemical characterization of wastes and porewaters in the comanagement units, site hydrogeologic characterization; groundwater sampling and analysis; and identification of land and groundwater uses in the vicinity of the site. The investigation centered on a 50-acre unlined primary ash pond constructed in 1967, a 46-acre lined secondary ash pond constructed in 1993, and surrounding areas. Historically, all coal combustion wastes were disposed of in the primary ash pond. Currently, bottom ash, economizer ash, boiler slag, drain sump wastes, and bottom ash tank overflow are conveyed to the primary ash pond. Fly ash, air heater wash water, coal area runoff, and demineralizer regenerant are conveyed to the secondary ash pond. The investigation concluded that there were no effects of comanagement observed because the low-volume wastes were either dilute in chemical composition or were volumetrically insignificant. Groundwater samples collected proximate to the unlined primary ash pond showed elevated levels of SO4 and B due to high-volume by-products. No effects on groundwater quality from high-volume by-products, low-volume wastes, or comanaged wastes residing in the secondary ash pond were observed