Hydrology, South Bay 1995 : data summary.

Abstract

Based on the results of the initial EM geophysical survey (summer, 1994) conducted north of the tailings disposal basin, and a subsequent preliminary test drilling and piezometer installation program during the fall of 1994, a buried valley was found, which appears to be the main path for subsurface contaminant movement from the tailings area in the direction of Mud Lake. Subsequently, Boojum Research obtained additional funding for further, much more extensive EM geophysical surveys and funding for an extensive test drilling and piezometer installation program. This latter program had as its objectives to ground truth the EM surveys and at the same time define the bedrock topography, the hydrogeological environment and the contaminant paths. The cost estimate for the test drilling and piezometer installation were prepared based on the objectives outlined above and submitted in November, 1994, prior to its submission to the client. Once all this information had been compiled and interpreted, design scenarios for remedial measures would be developed. The drilling and piezometer installation program was to be conducted during the late winter to ensure maximum mobility. Unfortunately, due to unforeseen climatic conditions, drilling and piezometer installation in the northern part of the Mud Lake basin was not possible, nor in any area with floating muskeg. As a result, the program was redesigned based on the new EM geophysical data and the same objectives, outlined above, for areas which were accessible during April/May, 1995. A total of ± 30 new testhole/piezometer locations were chosen. Cost estimates were obtained from a drilling company and their estimated cost fell within the estimate submitted in the fall of 1994. The testdrilling and piezometer installation program was carried out from April 25 to May 14, 1995. Subsequently, slug tests were conducted on the piezometers to determine the hydraulic conductivity. A total of 40 piezometers were installed. 24 (deep) piezometers were completed immediately above the bedrock surface, 9 shallow piezometers were installed in close proximity to the deeper ones, and an additional 7 shallow piezometers were installed in separated locations. All of the latter shallow piezometers are located in the vicinity of the northwestern part of the tailings basin. A total of 9 testholes (without piezometer installation) were drilled. The approximate location of the testholes is shown in Plate 1. Weather conditions during the fieldwork varied from a blizzard to + 20 0 C. The evaluation of the data and this report were delayed, because of inadequacies in the survey of the elevation and location of the new piezometers and testholes. Although, the problems with the survey data have not been solved yet, at the instruction of Boojum Research the interpretation of the data collected has proceeded.