Predicted Versus Actual Water Quality at Hardrock Mine Sites: Effect of Inherent Geochemical and Hydrologic Characteristics

Abstract

The Environmental Impact Statements (EISs) for 70 large modern-era hardrock mines in the United States were reviewed to determine their predicted impacts to water resources. EIS predictions were then compared to actual water quality conditions for 24 of the 70 mines (case studies), and the effects of geochemical characteristics and hydrologic conditions on operational water quality were evaluated. Nearly all case study mines with close proximity to water resources and moderate to high potential for acid drainage or contaminant leaching had operational water quality impacts ranging from increases over baseline concentrations to exceedence of water quality standards, with most having exceedences of standards. EIS water quality predictions made after considering the effects of mitigations largely underestimated actual impacts to groundwater, seeps, and surface water. EIS water quality predictions made before the ameliorating effects of mitigations were considered were more accurate at predicting operational water quality. Of the case study mines with these inherent geochemical and hydrologic characteristics, at least three-quarters underestimated operational water quality impacts in their pre-mining EIS predictions.

Measuring and Modeling Shallow Groundwater Flow between a Semi-Karst Border Stream and Ozark Forested Riparian Zone in the Central USA

“…Luo and Sophocleous [10] used HYDRUS -1D to estimate groundwater flow values ranging from -3.5 x 10 -8 to 3.5 x 10 -8 m 3 s -1 with a coefficient of determination (r 2 ) value of 0.75 between simulated and measured groundwater flow in an agricultural field located in Shandong province, China. A number of other numerical groundwater models (e.g CPFLOW, MODFLOW, SUTRA, HYDRUS and FEFLOW) [11] have been shown to successfully predict groundwater flow in varying hydrogeologic settings. Despite technological progress in modeling, previous authors indicated that improved model accuracy requires proper parameterization, emphasizing the need for higher resolution (spatial and temporal) field observations [12,13].…”

Pre-mining water quality prediction from non-weathered sulphide ores along the Ashanti metallogenic belt in Ghana using Acid-Base accounting procedure

“…The ABA test procedure determines the acid-producing and acid-neutralizing potentials of a test material (Sobek et al 1978). AcidBase Accounting is a highly projected and favoured geochemical characterisation method with a relatively short turn-around time; the procedure is very cost effective as compared with other methods (US EPA 1994; Maest et al 2005). By reason of the above qualities, ABA is often recommended for use at the exploration phase of mining projects for early decision making (McKenna et al 2009).…”

“…That notwithstanding, acurate prediction is recognized by both industry and government as a critical requirement for mines permitting and long-term operation (Maest et al 2005;Skousen and Ziemkiewicz 1996;MEND 2001).…”