Presentation outline What is selenium? Why is it increasing in the Elk River? Why should we care that it is increasing? How will Teck reverse the trend and eliminate the problem?
What is selenium? A semi-metallic (metalloid) element similar to sulfur that is found in some rocks, soil, coal, petroleum, etc. Complex chemistry, with four main chemical forms; converts from one to another (each with different chemical properties) Many industrial applications
Selenium biogeochemistry at Teck Coal mine sites Solid phase sources of Se Pyrite, Gypsum, sorbed SeO 3 2- Mineral surface SeO 4 2- Abundant organic carbon Se 0 biofilm Groundwater flow path SeO 3 2- Se 2- Pyrite, Fe(Se,S) 2 After Kirk, 2011 Organo-Se Sorbed SeO 3 2- Gypsum Ca(SeO 4,SO 4 ).2H 2 O Microbes Aerobic Facultative Anaerobic
What is selenium (contd)? An essential trace element for human and other animal nutrition that has a very narrow range between what is adequate and what is toxic Bioaccumulates readily, especially through aquatic food webs Largest step in bioaccumulation is from water to bottom of food web (like algae); typically may be 1000X
Selenium bioaccumulation from water (Source: Chapman et al. 2010)
What is selenium (contd)? From algae or suspended particulates to insects, typical bioaccumulation factor is 1 to 3X From insects to fish, typical bioaccumulation factor is ~1 to 1.5X From food to bird egg, typical bioaccumulation factor is 1.5 to 2X Selenium is transferred from the adult female fish or bird to her eggs; hence the concern for effects
Why is it increasing in the Elk River? Large masses of waste rock are moved to reach coal deposits in the Elk River watershed Selenium is released from the waste rock through interactions of oxygen, water, and microbes As the amount of waste rock increases, more selenium is mobilized to streams and ponds
BC Water Quality Guideline Highway 93 Sparwood 6% Increase Per Year Selenium concentrations in Elk River
Why should we care that it is increasing? Two main concerns are 1) potential effects on fish or birds (especially reproduction, the most sensitive endpoint) and 2) possible effects on people (from drinking the water at some upstream locations) Selenium cycles through the food web and gets accumulated, especially in ponds and lakes
Selenium Cycling in Aquatic Systems Note: Solid arrows indicate pathways by which selenium is remobilized from sediments into the foodchain. Source: Lemly and Smith (1987)
How will Teck reverse the trend and eliminate the problem? Teck commissioned the Strategic Advisory Panel on Selenium Management in 2010 to provide advice about sustainable mining practices The Panel produced a report with a series of recommendations based on input from diverse sources and evaluated options based on environmental, social, technical and economic criteria for sustainability
The Panels Process for Production of the Strategic Plan Establish the Panel Charter Goal and objectives Conflict of Interest policy Performance measures Schedule Information Gathering and Analysis Two Panel Sub-Groups: Technical and Stakeholder Tours of Elk Valley and Cardinal River operations Corporate Risk Assessment Stakeholder Mapping Stakeholder Engagement Fernie and Hinton Workshops Structured Decision-Making Production of the Report Stella Swanson, Chair Rob Abbott Wes Funk Lisa Kirk Gord McKenna Tom Sandy Harry Ohlendorf
Mitigation methods for sustainability of mining Water treatment Treat mine effluent waters Water management Reuse Se impacted water Divert clean water around rockdrains Divert clean run-on water away from dumps Reduce infiltration with dump covers Dump design to reduce Se loading Maximize pit backfill Selectively handle and encapsulate Se material Eliminate Se material in rock drain cross valley fills In situ microbial source control Interbed CCR/tails with waste rock Control oxygen, moisture, lithology (carbon) to affect reduction Mine planning Change from surface to underground mining Design facilities for both resource recovery and waste management through selective handling, sequencing, and placement
Teck actions Adopted Panel recommendations Created two full-time selenium management positions Withdrew plans for Line Creek Mine expansion to reevaluate selenium management actions Initiated water treatment pilot testing and water diversion projects, plus evaluation of other capital projects Developing a research and development program to address uncertainties
Your consent to our cookies if you continue to use this website.