British Columbia Mine Reclamation Symposium

A risk assessment / risk management perspective on mercury contaminated sediments in mining affected Pinchi Lake, BC Mann, Gary S. (Gary Seymour), 1966-; Baker, Randy F.; Allard, P. J.


The Pinchi Mine, located on the merciferous Pinchi Fault region of BC, produced metallic mercury from 1940 to 1944 (historical operation) and from 1968 to 1975 (modern operation). Between 2010 and 2012, the mine underwent decommissioning and reclamation to ensure that the terrestrial areas affected by the mine do not pose unacceptable risks to ecological resources. The historical operations included placement of roasted ores (calcines) in Pinchi Lake adjacent to the site, resulting in highly elevated mercury concentrations in nearshore sediments (subsurface calcines). This source, as well as aerial deposition of elemental Hg during the roasting process during both operations, broadly elevated sediment mercury concentrations throughout the lake. In 1997, inorganic and methylmercury concentrations were measured in pore water and sediment at different depths in sediment cores and showed that subsurface calcine sediment was a significant contributor of inorganic mercury to the lake, notwithstanding slow burial by cleaner sediments. In 2001, a sediment quality triad (chemistry, toxicity, benthos) study showed no correlation between sediment inorganic mercury concentration, toxicity or benthic community structure. However, benthic organisms living in subsurface calcine sediment were elevated in total and methylmercury concentrations relative to benthos elsewhere in the lake. This paper reviews and integrates historical sediment investigations using a risk assessment and risk management framework to guide further investigations and support long-term decision-making regarding Pinchi Lake sediment.

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