British Columbia Mine Reclamation Symposium

Decommissioning open pits with ecological engineering Kalin, Margaret


Ecological Engineering, a biotechnological approach to the decommissioning of base metal mining wastes, is being tested on two open pits (Gloryholes) in Newfoundland, Canada. Pit #1 has a volume of 208,000 m3 (pH ranges between 5.5 and 7). Pit #2, with a volume of 66,200 m3, has an average pH of 3.5. Organic substrates are used to form sediment and provide carbon and nutrients for microbial ecosystems which reduce sulphate and generate alkalinity. Enclosures (4 m diameter and approx. 3.5 m depth) were placed in both pits to test the suitability of different organic amendments (peat and sawdust) as carbon and nutrient sources. Microbial alkalinitygeneration was evident 95 days after placement of the amendment on July 4, 1989. Zinc concentrations in the enclosures in Pit #2, dropped from an average of 35 mg/L to about 2 mg/L or less by day 480, and by day 300 in Pit #1. A scaled-up experiment has been under way since August 25,1990, where 390 m3 are treated in Pit #2 and 750 m3 in Pit #1. Research continues on the determination of factors which can limit the ARUM process.

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