Name of Project: Phase III and Mine Site Remedial Options Analysis
City and province: Sudbury, Ontario
Client: Vale (Inco)
Client Sectors: Mining
This multi-million dollar project involved expert engineering and environmental evaluations for a comprehensive groundwater characterization study of 16 mine sites and mine processing sites in Ontario. It involved the installation and testing of nearly 1000 monitoring wells in overburden and bedrock. These studies were required to characterize groundwater conditions in support of mine closure plans under Regulation 240 and the Mine Rehabilitation Code of Ontario.
The study consisted of identifying potential source areas such as tailings facilities, concentrator tanks, smelting complexes and refinery operations. Surface geophysics was conducted at each site in order to define buried bedrock valleys which were considered to serve as the primary groundwater pathways. The locations of monitoring wells were selected on the basis of source areas, knowledge of the local geology, the locations of nearby receptors, and information obtained during the surface geophysics work.
Monitoring well nests were drilled using a combination of hollow stem auger drilling for shallow overburden and air rotary drilling for deeper overburden and bedrock wells. Borehole geophysics (gamma, conductivity, EM) was conducted on the deepest borehole at each nest location so that zones of elevated conductivity could be identified for placement of shallower well installations. The monitoring well nests generally consisted of a bedrock contact well constructed across the overburden/bedrock interface at depths generally in excess of 30 m below ground surface, and shallower wells above the contact well located to intersect permeable zones (sand and gravel) or zones of elevated electrical conductivity based on the borehole geophysics. Each monitoring well was developed and sampled for a wide range of inorganic parameters indicative of base metals mining impact. Each well was subjected to a single well response test (rising or falling head test) so that hydraulic conductivity data could be obtained.
WESA also conducted remedial assessments at a number of the facilities. These assessments involved identifying options for mitigating impacts and preparing Level D cost estimates for the various options.
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