Reconstruction of forested ecosystems on rock disposal sites at Mount Polley Mine

Mount Polley Mining Corporation, operated by Imperial Metals Ltd, is located in the Fraser Plateau physiographic region in central British Columbia, approximately 56 km northeast of Williams Lake and 8 km southwest of Likely. The mining method employed is open-pit mining of a gold/copper porphyry deposit. Reclamation research has been conducted since 1998 to develop innovative techniques for restoring sustainable forest ecosystems and critical wildlife habitat. In 1998 and 1999, a total of 12 treatments in triplicate were established on top of the 1,170 m dump. In 2000, an additional 12 treatments were established on the side slope of this dump. The treatments were established to evaluate the following variables, parameters and components: depth of topsoil required to meet reclamation objectives; suitability of tailings and biosolids as a growth medium; selection of tree species for reclamation objectives; interaction of vegetation competition with tree survival and growth; extent of metal uptake by vegetation; and vegetation relationships to various soil amendments. The trials were measured in 2006, and detailed statistics were generated. The analysis indicates the following: a minimum of 15 cm of soil is required to established trees; there is a significant positive response to tree growth to a soil depth of 40 cm, and thereafter no significance in growth is seen with increasing soil depth; 40 cm of soil amendments is currently meeting tree growth objectives; there is a positive response in tree and vegetation growth to biosolids amendments on the 1998 and 1999 trial, but no response in seen on the 2000 trial; tree mortality is significantly higher (α=0.05) with biosolids amendments for all trials (ammonia toxicity to the young seedlings is suspected); vegetation competition is also a significant negative factor in seedling survival and growth (vegetation growth is directly related to available soil nutrient supply); and vegetation cover and diversity increased with increase in soil amendment depth or addition of biosolids. This paper presents the 8-to-9-year results of vegetative growth of this trial, examines the effects of combinations of variables and proposes further investigation to more specifically describe the causes of the results observed.Non UBCUnreviewedOthe