Controlling Acid Drainage in a Pyritic Mine Waste Rock. Part I: Statistical Analysis of Drainage Data

Field experiments were conducted to evaluate the relativeeffectiveness of several covers and amendment techniques forpreventing or controlling acid generation in a pyritic minewaste rock. The covers and techniques consisted of water cover,soil cover, wood bark cover, limestone addition and phosphaterock addition. Water quality data (pH, sulphate, zinc and ironconcentrations) obtained from the experiments were analyzedusing two-way ANOVA (analysis of variance) with repeatedmeasurements. A 5% test of significance (p-value of 0.05) wasused in the analysis. The results suggested that the covers andamendments should be either compared on a time-by-time basis orgrouped into four, based on their performance: (i) water cover, (ii)1% and 3% limestone, (iii) clay, 1% and 3%PO₄, andcontrol (no cover), and (iv) wood bark. The results did not showany significant difference between the drainage quality from1% and 3% limestone-amended rocks. The drainage quality from the 1%and 3% phosphate and clay-covered rocks did not significantlydiffer from the control (unamended) rock. Water cover was foundto be the most effective, while the wood bark cover proved to bean ineffective method for controlling acid drainage in the wasterock. The statistical analysis also showed good replication inthe experiments, as no significant difference in the quality ofthe drainage from the replicates was observed.