Review of 23 years of STD: Island copper mine, Canada

The submarine tailings disposal (STD) system at Island Copper Mine has been subjected to a comprehensive environmental monitoring program initiated in 1970, some 20 months before the mill started processing ore. The program has been extended and modified as new factors became relevant or it became clear that particular factors were not of concern at this site. The major environmental issues have concerned (1) tailings resuspension and upwelling, (2) smothering of benthos, and (3) trace metal contamination from acid rock drainage (ARD). A closure plan has been prepared for implementation in 1995. Tailings were resuspended and upwelled to surface close to the fiord sill due to unpredicted periodic high‐density tidal jets scouring the deposits at that point. The localized elevated turbidity has not affected biological productivity. Benthos have been smothered under rapid tailings deposition such that areas under thick tailings ( > about 20–30 cm) showed reduced biodiversity. At deposition rates of < l cm p.a...