Effects of changing environmental rules : Kitsault molybdenum mine, Canada

The Kitsault mine was reopened briefly in 1981–82, after prior operations in 1967–72. Initial oceanographic assessments showed that a submarine tailings disposal (STD) system similar to that at Island Copper Mine would function to produce a tailings density current that would deposit on the fjord bed. There was substantial community interest and action during the final years of the development at a time when new pollution controls were being developed in Canada. The STD system essentially met its design criteria, but new oceanographic instrumentation at the time showed some contribution of tailings at the outfall discharge point to a naturally present mid‐water turbidity layer. The first intensive postclosure monitoring of ecosystem rehabilitation following STD use anywhere in the world was undertaken between 1983 and 1989. Soon after closure in 1983, pore waters in the submerged deposited tailings were observed to be enriched in molybdenum, which must have supported an efflux of the metal to the overlyin...