Basic Terms and Knowledge: 24-MMP-A6 Mining and the Environment, May 2015, Q3

Question 3: Basic Terms and Knowledge (20 marks, OPTIONAL)

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.

a) True/False (2 marks each, 10 marks total)

True/false statements on Canadian mine-waste and mining-rights regulation
#	Statement	Answer	Explanation
a)	Subaqueous tailings disposal to fresh water lakes is allowable in Canada.	True	Schedule 2 of the MDMER (the exam's "MMER"), under the Fisheries Act, permits a listed mine to use a natural fresh water lake as a Tailings Impoundment Area, provided the lake is added to Schedule 2 through a formal federal regulatory amendment and the operator meets prescribed effluent limits, fish habitat compensation and long-term monitoring conditions – several Canadian gold and base-metal mines (e.g. historic and some current operations) have used this permitted-but-tightly-controlled pathway.
b)	Mineral and mining rights fall under federal jurisdiction.	False	Under ss. 92A and 109 of the Constitution Act, 1867, ownership, management and disposition of Crown minerals within a province are provincial powers – each province administers its own mineral tenure, leases and mining permits. Federal jurisdiction over minerals is the exception, limited to the territories, federal/reserve lands, uranium, and some offshore areas.
c)	Federal environmental approval is required for most mining projects in Canada.	False	A federal impact assessment under the Impact Assessment Act (successor to the 2012 Canadian Environmental Assessment Act) is triggered only when a project meets a prescribed capacity or physical threshold on the Physical Activities Regulations. The great majority of mining activity in Canada – exploration and many smaller operations and expansions – proceeds through provincial environmental assessment and permitting alone, so federal review is the scale-triggered exception rather than the norm.
d)	Mine sites in Canada are not allowed to discharge effluent to the environment.	False	The MDMER is a permission-with-limits regime, not a prohibition: a mine listed on Schedule 2 may deposit effluent (including tailings) to a fish-frequented water body provided it meets prescribed authorized concentration limits (arsenic, copper, lead, nickel, zinc, un-ionized ammonia, total suspended solids, radium-226) and undertakes an Environmental Effects Monitoring (EEM) program.
e)	Progressive reclamation is a requirement under the Mining Act, or equivalent legislation, in your Province.	True	British Columbia's Health, Safety and Reclamation Code for Mines requires a Mines Act permit holder to progressively reclaim disturbed land as mining advances rather than deferring all reclamation to final closure, and to maintain reclamation security calculated to reflect the current, unreclaimed disturbance – equivalent progressive-reclamation obligations exist under Ontario's Mining Act and other provincial mining statutes.

b) Definitions (all seven terms defined; any five satisfy the mark scheme)

Definitions of risk-assessment and geotechnical terms
Term	Definition
Consequence (risk management perspective)	The outcome or severity of harm (loss of life, environmental damage, financial or reputational loss) that WOULD result if a given hazard event actually occurred. Risk is conventionally expressed as $\text{Risk} = f(\text{Likelihood}, \text{Consequence})$, and it is exactly this consequence classification that the Canadian Dam Association uses to set a tailings dam's design flood, design earthquake and inspection frequency.
Plasticity index	The numerical range of water content over which a fine-grained soil behaves plastically: $PI = LL - PL$, where $LL$ is the liquid limit and $PL$ the plastic limit. A tailings sample with $LL = 42\%$ and $PL = 24\%$ has $PI = 42-24 = 18\%$; a high PI indicates a highly plastic, compressible, low-permeability clay, while a PI near zero indicates a non-plastic silt or sand more prone to liquefaction.
Atterberg limits	A set of standardized water-content boundaries – the shrinkage limit, plastic limit (PL) and liquid limit (LL) – that mark the transitions of a fine-grained soil between solid, semi-solid, plastic and liquid consistency states, determined by the Casagrande cup/fall-cone (LL) and thread-rolling (PL) tests. They are the standard classification framework for tailings and foundation soils and the basis of the plasticity index above.
Standard Proctor Compaction Test	A laboratory test (ASTM D698) that compacts soil at a series of moisture contents into a mould using a standardized hammer, drop height and number of blows, plotting dry density against moisture content to find the "optimum moisture content" that yields the maximum achievable dry density. It sets the compaction target and field moisture-conditioning specification for constructing an engineered fill, embankment core or till cover.
Darcy's Law	The governing equation for laminar seepage flow through a porous medium: $q = -k\,\dfrac{dh}{dx}$, where $q$ is the specific discharge, $k$ the hydraulic conductivity of the material and $dh/dx$ the hydraulic gradient. It is the physical basis for locating the phreatic surface within a tailings embankment and for calculating the seepage quantity a collection ditch or underdrain must handle.
Hazard	A source of potential harm, damage or loss – for example a tailings dam breach, an underground mine gas outburst, or an unstable pit wall – considered purely as an event that COULD occur, independent of how likely it is. Identifying hazards is the first step of any risk assessment, before likelihood or consequence is estimated.
Probable maximum flood (PMF)	The largest flood that could conceivably occur at a given catchment, derived by routing the Probable Maximum Precipitation (the theoretical upper limit of precipitation for the region and season) through a hydrologic model of the catchment. It is used as the design inflow flood for the highest consequence-classification tailings and water-retention dams, since these structures must safely pass or store an event with no defined statistical return period.

Topic. Foundational Canadian mine-waste governance vocabulary and the geotechnical/hydraulic terms risk assessment and dam design are built on.

Key relations. $PI = LL - PL$; Darcy's law $q = -k\,dh/dx$; $\text{Risk} = f(\text{Likelihood}, \text{Consequence})$.

Why this works. Statutory instruments (MDMER under the Fisheries Act, provincial Mines Acts) create legal obligations enforced by government inspection and prosecution, while these same terms – hazard, consequence, PMF – give engineers a shared vocabulary to translate a geotechnical or hydrologic finding into the design basis a regulator or dam classification system requires.

Common pitfall. Confusing a hazard (the dam breach event itself) with its consequence (what would be lost if it occurred) – the CDA's consequence classification system depends on keeping the two distinct; and assuming subaqueous disposal is categorically banned in Canada, when it is in fact a permitted (if tightly regulated) Schedule 2 pathway.

Source. Constitution Act, 1867, ss. 92A, 109; MDMER under the Fisheries Act; BC Health, Safety and Reclamation Code for Mines; Canadian Dam Association, Dam Safety Guidelines (PMF as design basis).

Question 3 of 6: Basic Terms and Knowledge

Question 3: Basic Terms and Knowledge (20 marks, OPTIONAL)

a) True/False (2 marks each, 10 marks total)

b) Definitions (all seven terms defined; any five satisfy the mark scheme)