Environmental Releases
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Overview
Smelter operations generate various emissions, effluents, and solid wastes. Permits and regulations limit the amount of releases; set out handling and disposal procedures; and establish measuring, monitoring and reporting requirements.
Rio Tinto Alcan continually works to minimize and mitigate any impact of its releases, by better understanding their nature and extent and by limiting their generation and release.
Management of releases has a significant bearing on environmental conditions, particularly in and around operating communities, and the releases associated with particular products are of growing marketplace and consumer interest.
Strategies and Initiatives
Overall Performance: Raw material and weather-related challenges in 2007 resulted in a second consecutive year of elevated environmental releases and permit non-compliances. Given changes in global markets, it is likely that raw-material supply challenges will continue and Rio Tinto Alcan Primary Metal BC is working on a variety of solutions to minimize their impacts.
Fluoride Emissions: There were six non-compliances with the monthly fluoride emissions permit level during 2007 – all of which are attributed mainly to continued quality issues relating to available coke and alumina, and their impacts on process stability. Fluoride emissions are known to have some impacts on vegetation in the immediate vicinity of the smelter.
Coke, a petroleum-manufacturing byproduct, is used to make the anodes that are consumed in the smelter’s potrooms. As energy prices continue to rise, refiners are extracting more fuel from crude oil. This results in lower-density coke and weaker anodes, and creates a greater likelihood of fluoride emissions as the anodes are consumed.
Rio Tinto Alcan Primary Metal BC also continued to receive off-specification alumina shipments during 2007, following a major upgrade undertaken by the smelter’s main alumina supplier and at a time when alternative sources were limited. Aluminum is extracted from alumina in the potrooms, and alumina quality has a big impact on process stability and therefore emissions in general.
As a result of the fluoride emission challenges in 2007, an Escalating Control Plan (ECP) was developed and implemented to address both coke and alumina issues. It involves the continual monitoring of variables that impact fluoride-emission levels, and a tiered response plan pegged to defined levels of risk.
Variables include the number of “exception pots” – those operating outside defined process-stability parameters – and the quality of the anodes being consumed in the potroom at a given time. Responses include personnel and equipment availability and operating-procedure changes to facilitate effective emissions control.
The ECP also involves plant-wide awareness programs, which have improved understanding of the status and implications of fluoride-related performance. ECP implementation is believed to have significantly reduced fluoride emissions in the final quarter of 2007.
Effluents: High-precipitation events and snow accumulation during 2007 strained the capacity and efficiency of the effluent treatment system, and contributed to higher levels of dissolved fluoride, aluminum, and total suspended solids.
High precipitation resulted in overflows at two treatment lagoons on January 24, and in three effluent-related permit non-compliances. A further overflow occurred on March 29, but modifications made after the January incident successfully contained it.
Several effluent-related projects were proceeded with in 2007. This included continuation of the J-stream diversion project (designed to bypass a source of fluoride contamination), expanded groundwater measurement and monitoring, and a capacity and treatment-efficiency assessment of the existing lagoon system.
Permit Non-Compliance and Spill Summary
There were 11 permit non-compliances in 2007, down from 14 in 2006. As noted above, six related to fluoride emissions and three to effluents. The other two involved a procedural error that allowed a bear to access an incinerator building, and an exceedance of an asbestos-disposal limit. Eight spills were reported to the British Columbia Ministry of the Environment, up from four in 2006. One involved a release of propane gas, while two occurred into the marine environment and five into fresh water and involved various substances. Details with respect to causes and corrective actions are available in the Rio Tinto Alcan Primary Metal BC Annual Environmental Report.
