An Approach to Using Geochemical Analysis to Evaluate the Potential Presence of Coal Ash Constituents in Drinking Water

摘要

A geochemical evaluation approach was developed to compare water quality data collected from monitoring wells located within,upgradient,and downgradient of a hypothetical coal ash pond system to determine the degree to which local water supply wells were affected by ash pond constituents.The data set for the system was generated based on general water quality characteristics found in vicinity of a typical ash pond system,which was comprised of water samples collected from: ash pond monitor wells,monitor wells screened in the saturated zone below the ash ponds;monitor wells located upgradient and downgradient of the ash ponds;and nearby water supply wells.Use of a series of geochemical plots allowed for identification of indicator compounds tied to the oxidation reduction state of the sampled water and to common coal combustion residual(CCR)indicator constituents such as sulfate and boron.A parallel statistical analysis was performed to determine background threshold values(BTVs)for CCR constituents using site-specific and regional data.A comparison between the BTVs for each compound and the water supply well data was performed to determine whether water supply wells contained naturally occurring levels of inorganics or whether the detected inorganics were CCR-derived and due to migration from the ash pond systems.The results indicate that the approach can provide strong evidence to help determine whether off-site water supply wells are or not impacted by CCR releases to groundwater.