24-MMP-A6 Mining and the Environment · May 2015
Nivaar worked solution (AI-drafted; not reviewed by a licensed engineer)
EGBC National Exam — Mining and Mineral Processing Engineering, 09-MMP-A6 Mining and the Environment, 2015-May. 3 hours duration, open book (any non-communicating calculator permitted). FIVE questions constitute a complete exam paper: Questions 1 and 2 are MANDATORY, and THREE questions must be selected from the OPTIONAL Questions 3 to 6, with only the first three optional answers appearing in the answer book marked. Most questions require a full-sentence or bullet-point response.
Reference texts: BC Ministry of Energy, Mines and Low Carbon Innovation, Health, Safety and Reclamation Code for Mines in British Columbia (current edition) (permitting, reclamation and closure planning requirements); Canadian Dam Association (CDA), Dam Safety Guidelines (2013/2019 update) (dam classification, tailings dam consequence categories, dam safety review and inspection intervals); Global Industry Standard on Tailings Management (GISTM, 2020) (tailings governance, design and closure principles); Price, W.A., MEND Report 1.20.1, Prediction Manual for Drainage Chemistry from Sulphidic Geologic Materials (1997/2009) (acid-base accounting, NPR screening criteria, ARD prevention and treatment); International Network for Acid Prevention (INAP), Global Acid Rock Drainage (GARD) Guide (ARD prediction, prevention, treatment and waste rock encapsulation design); Government of Canada, Metal and Diamond Mining Effluent Regulations (MDMER, the current name for the exam's "MMER") under the Fisheries Act; Government of Canada, Impact Assessment Act (successor to the 2012 Canadian Environmental Assessment Act); Government of Canada, Canadian Environmental Protection Act, 1999 (National Pollutant Release Inventory); Mining Association of Canada, Towards Sustainable Mining Tailings Management Protocol; International Cyanide Management Institute, International Cyanide Management Code; ATSDR, Toxicological Profiles for polycyclic aromatic hydrocarbons, mercury, lead and cyanide.
Question text not reproduced: the examination questions are © Engineers and Geoscientists BC. Open the official past paper (linked at the top of this page) to read the question, then follow the worked solution below.
| Substance | Transmission & health effects |
|---|---|
| Polycyclic aromatic hydrocarbons (PAHs) | Generated by incomplete combustion – diesel exhaust from the haul truck and equipment fleet, blasting fumes, and coal or carbonaceous ore handling – PAHs are transmitted primarily as airborne particulate-bound compounds inhaled directly by workers, and secondarily via deposition onto soil, snowpack and surface water where they adsorb strongly to organic matter and bioaccumulate up the food chain. Several PAHs (notably benzo[a]pyrene) are classified human carcinogens, with chronic exposure linked to lung, skin and bladder cancers, and acute high exposure causing skin and respiratory irritation. PAHs are most closely associated with coal mining and any operation with a heavy diesel equipment fleet, blasting program, or on-site fuel/explosives storage, rather than with a specific ore mineral. |
| Mercury | Historically released from gold ore processing (amalgamation, now largely phased out in regulated jurisdictions, though legacy tailings remain a source) and as a trace contaminant volatilized during roasting or smelting of mercury-bearing sulphide ores; transmitted as elemental vapour (inhaled directly) and, once deposited to water, converted by anaerobic bacteria to highly bioaccumulative methylmercury that concentrates up the aquatic food chain into fish. Chronic exposure causes neurological damage (particularly to developing fetuses and children), with methylmercury-contaminated fish consumption the dominant human exposure pathway near affected sites. Mercury is most commonly associated with gold and, secondarily, mercury-bearing base-metal sulphide deposits. |
| Lead | Released from lead-zinc sulphide ore (galena, PbS) mining and milling as fugitive dust from ore handling, crushing and tailings surfaces, and historically from smelter stack emissions; transmitted by direct inhalation of lead-bearing dust and by ingestion of contaminated soil, dust or drinking water, with children particularly vulnerable to hand-to-mouth soil ingestion near legacy sites. Chronic lead exposure causes neurodevelopmental damage in children (IQ deficits, behavioural effects) and, in adults, hypertension, kidney damage and reproductive effects, with no safe threshold of exposure identified. Lead is most closely associated with lead-zinc (galena-sphalerite) ore bodies and their historic smelter operations. |
| Cyanide | Used as a lixiviant in gold and silver cyanidation (heap leach and mill circuits), cyanide is transmitted primarily via accidental release to surface water (historically the dominant pathway in major mining incidents such as Baia Mare, 2000) and, to a lesser extent, as HCN gas volatilized from an open tailings pond under acidic conditions. Free cyanide is acutely toxic, inhibiting cellular respiration (cytochrome oxidase) and causing rapid death in exposed fish and wildlife at low concentrations, and is acutely lethal to humans at sufficient dose via inhalation or ingestion, though it does not bioaccumulate or persist in the environment the way mercury or PAHs do. Cyanide use is specifically associated with gold and silver ore processing, which is why the International Cyanide Management Code (Question 4) exists as a gold-industry-specific instrument. |
Open pit haul roads – chemical dust palliative (hygroscopic salt or polymer binder). A hygroscopic salt (magnesium or calcium chloride) or a lignosulfonate/polymer binder is applied to the haul road surface, where it either draws and retains atmospheric moisture (hygroscopic salts) or binds surface fines into a crust (polymer binders), resisting the constant mechanical abrasion of loaded haul truck traffic. Its advantage over water spraying is durability – a treated road holds down dust for days to weeks rather than the hours a water truck pass lasts, cutting water-truck fleet size, fuel burn and the haul-road maintenance downtime water trucks otherwise compete for with production traffic. Its drawbacks are that chloride salts are corrosive to truck bodies, tires and steel structures and can themselves leach to groundwater or surface water requiring monitoring, and the treated crust still degrades under continuous heavy-truck loading, so reapplication on a recurring schedule and cost is required.
Active waste dumps/tailings impoundments – wind fencing / porous windbreaks. Porous fence panels or engineered windbreaks are installed along the windward perimeter of an actively-growing dump face or a drying tailings beach segment, reducing wind velocity at the exposed surface below the threshold needed to entrain fine particles, without requiring any liquid or chemical application to a surface still receiving fresh material. Its advantage is that, unlike a chemical palliative or vegetative cover, it can be used on a surface that is actively growing or still wet/unconsolidated, is comparatively low capital cost, and is readily relocated as the active face advances. Its main drawbacks are that it only reduces (not eliminates) dust generation, its effectiveness depends strongly on wind direction and fence orientation relative to the prevailing wind, and it provides no benefit against dust generated by direct equipment traffic on the surface itself, unlike a surface-applied palliative.
