Preventing Acid Mine Drainage with an Elevated Water Table: Long-Term Column Experiments and Parameter Analysis

Abstract

The elevated water table (EWT) technique for preventing acid mine drainage (AMD) was tested using instrumented laboratory columns containing reactive tailings from the Louvicourt and Sigma mines, Abitibi, Quebec. The tests were performed in short (0.4 m) and long (1.4-1.7 m) columns over 400-500 days and included periodic surface recharge and subsequent monitoring of the leached drainage water. In each column, the water table depth was adjusted relative to the air entry value (AEV or y a ) of the tailings. The influence of different water table elevations was evaluated by measuring the effluent pH, as well as the concentrations of major ions including sulphate, iron, zinc, copper and lead. Provided the water table depth below the tailings surface remained less than one half of the tailings' AEV, the observed data showed that an EWT can be very effective in reducing acid mine drainage. The principal factors controlling drainage quality were the saturated hydraulic conductivity (k sat ) and the air entry value (y a ) of the tailings. A lower k sat and a higher y a in the tailings tend to increase the performance of an elevated water table by limiting drainage-induced desaturation. Mineralogical composition had relatively little effect on the hydrogeochemical evolution provided the tailings remained highly saturated (S r ≥90%). The results presented here indicate that an elevated water table can be an effective means for controlling the production of AMD when the design conditions are properly selected and applied.

Short-term forecasting of groundwater levels under conditions of mine-tailings recharge using wavelet ensemble neural network models

“…The rehabilitation method applied to this site is based on the elevated water-table technique (Ouangrawa et al 2010). This method is based on strategically covering existing acid-generating tailings with neutral material, provoking a raised water table beyond the neutral/ reactive tailings interface and assuring a sufficiently high degree of capillary saturation within the tailings above the water table in order to inhibit sulphide oxidation.…”

Review of the Reclamation Techniques for Acid-Generating Mine Wastes upon Closure of Disposal Sites

“…h < AEV, as illustrated in Fig. 6 (Aubertin et al 1999;Ouangrawa et al 2010;Pabst 2011). Raising the water table is easier when the impoundment was designed to prevent exfiltration.…”

Preliminary geotechnical assessment of the potential use of mixtures of soil and acid mine drainage neutralization sludge as materials for the moisture retention layer of covers with capillary barrier effects

“…Pabst et al 2011Pabst et al , 2014. The long-term efficiency of single-layer covers as an oxygen barrier is improved when the covers are used in combination with an elevated water table (MEND 1996;Ouangrawa et al 2010;Pabst et al 2011Pabst et al , 2014. Water table located in the tailings and higher air-entry values of the cover materials can help to maintain water saturation and to reduce oxygen fluxes.…”