- Comminution (CM)
Comminution is the process of crushing and processing ore into smaller particles, and can consume 50% or more of a mine’s energy. Several methods, using up to 4 stages, and varying degrees of automation are available. Comminution methods are also “ore-dependent”. According to “Mining[dot]com” “There is no magic design that is the best for all (comminution) circuits”. Generally, the more comminution upstream (in the initial stages) the better. However, the more stages involved, the more energy is consumed, resulting in an overall higher environmental cost. Therefore, the question asks: “Where does the bulk of the process occur: Upstream/in-pit, using High Pressure Grinding Rolls “HPRG” which may include “Pre-Screening” or is it spread along a multi-stage process? If the mine uses significant Upstream or In-Pit HPGR, ENTER “1” – If the mine is more reliant on Traditional “SAB” (Autogenous and/or Semi-Autogenous + Ball Milling) ENTER “2”. If the mine has a 3 – 4-stage process (Traditional + “Vertimill” or equivalent) with little to no HPGR, ENTER “3”.
- Company Profile (Co)
1 - High 2 - Average 3 - Low 4 - Poor
All companies behave differently. FMC's basic scale from 1- 4 is based on the record of Indigenous engagement and community relations in general; history of maintenance issues/inspection orders; and history, nature, and gravity of regulatory violations.
- Concentration (SL)
Once crushed, valuable minerals are separated from the ore using different methods of Concentration, alone, or in combination: Gravity – Floatation – Optical – Magnetic – Electrostatic. The question is concerned with environmental impact and the production of tailings. The Froth Floatation method produces the most wet tailings. If the mine uses LESS Floatation and Gravity separation and MORE Optical and/or Electrostatic/Magnetic ENTER “1”. For a combination ENTER “2”. For a mainly Froth Floatation concentration system ENTER “3”.
- Dam Design (TSF)
Primary TSF or mean TSF dam design method. If this mining project has a TSF, enter the risk factor number for its design in this space. For a good explanation of different TSF dam designs see: ICMM
1 - Thickened 2 - Downstream 3 - Centerline 4 - Upstream
Many mines incorporate one or more of the three main types of dam designs in a single TSF (Downstream, Centreline, Upstream) - from the original design through subsequent raises. If different methods are used in a single TSF Pond, apply the average. Category “1” or “Thickened” tailings may still require a small embankment and are not considered pure “Dry-Stack” (>84% solids by weight)”. If your mine’s TSF is “Dry-Stack” – SKIP THIS SECTION.
- Dry-Stack (DS)
De-watering of tailings until they achieve “dryness" required for Dry-Stacking really begins in the production chain. However, if a Dry-Stack is achieved by the mine (>84% Solids by Weight), several technologies are available to maintain the Dry-Stack. They vary from the use of “Geotubes” – “Zero Water Flux” and “Oxygen Limiters” to manage water balance. ENTER “1” if your mine uses 3 or MORE methods – ENTER “2” for 2 methods, and ENTER “3” if it relies on a sole method for Dry-Stacking.
- Embankment Slope (ES)
Each embankment has its own Static Factor of Safety (FoS) – the ratio of the forces of resistance to the shear forces acting on the dam. See the Health, Safety and Reclamation Code “Guidance Document”.
The FoS is related to the slope of the embankment (H: horizontal – to V: vertical) and should be easy to obtain from publicly available mine data. If your mine uses a Dry-Stack you may SKIP THIS SECTION. Otherwise, this scale presents 4 FoS options from Best to Worst: >1.5 / 1.5 / between 1.3 to <1.5 / and <1.3.
- Liner Type (LT)
1 - Engineered 2 - Partial 3 - None
For all Tailings Storage Types. A Dry-Stack, as well as a TSF pond(s), may or may not have a bottom liner, or layers of filtration to protect groundwater. These are made from different materials, some manmade, some natural. ENTER “1” for an engineered liner with 3 (or more) layers of fabric and/or filtration material); ENTER “2” for a partially engineered (1 or 2 layer) liner; and ENTER “3” if the TSF has no significant liner or filtration layer.
- Natural Area Value (NAV) - dollars ($) / hectare (ha)
The Natural Area Value (“NAV”) is obtained by calculating the per-hectare average price of a hectare of land in your jurisdiction. In British Columbia, this was obtained by calculating the per-hectare average of 4 purchases by BC Parks, 23 purchases by the Greater Vancouver Regional District, and the complete record of acquisitions by the Capital Regional District - all made to convert private land to parks and other green spaces, as shown in Table IAV 1, on page 2 of "Impact Area Value - Part II". The average was $14,610 CAD per hectare (rounded up to $15,000 CAD).
- Piping (PIPE)
1 - Basalt Coated Steel 2 - Steel
Wet tailings are pumped through steel pipes. Most mines rely on standard duplex steel piping which is highly prone to corrosion and incrustation, and requires more maintenance over coated pipes.
- Precipitation Zone (PZ)
1 - Low 2 - Low/Med 3 - Medium 4 - Med/High 5 - High
For British Columbia FMC uses a scale of 1-5 from the University of British Columbia Department of Geography Fig.2 - "Continentality Effect: Distance from the Pacific Coast".
- Previous Impact Area (PIA) - hectares (ha)
The Previous Impact Area (PIA) is the area of all prior human development (mines, utility corridors, cities, towns, farms, mineral and forestry leases) which factor into the Grand Impact Area Value (in hectares).
- Project Footprint (PF) - hectares (ha)
The Project Footprint ("PF") is the legal area of the mine. Use a map of the mine plan for your reference, or estimate.
- Project Impact Footprint (PIF) - hectares (ha)
All mining activities affect the land and water beyond legal boundaries. To account for the “Project Impact Footprint “(“PIF”) we chose an area 4-times greater than the mine’s property or Project Footprint (“PF”). These areas may not feel the direct effect of excavations or tailings storage, but the peripheral area endures seepage, dust, noise, and general disturbance to the natural area that would not exist but for the presence of the mine or mining activity. You may also multiply your PF by 4, or use another Project Footprint factor more indicative of your mine's impact.
- Pumps (PUMP)
1 - Positive Displacement 2 - Centrifugal
Two main types of pumps are used to pump wet tailings: Centrifugal (most common, least expensive, highest maintenance) and Positive Displacement pumps which are less common, mainly because of their higher up-front cost.
- Seismic Zone (SZ)
1 - Low 2 - Low/Med 3 - Medium 4 - Med/High 5 - High
For British Columbia, FMC uses the Natural Resources Canada definitions.
- Sizing (SI)
Technological advances have allowed for high-speed, electronic scanners to sort ore particles as they make their way through the production chain. If the mine uses a full-automated image analysis /scanning process ENTER “1”. If it uses a combination of automated and passive systems ENTER “2”. If the mine uses no automated screening/sorting technology ENTER “3”.
- Solids By Weight (SBW)
De-watering of tailings until they achieve “dryness’ required for Dry-Stacking really begins in the production chain. However, if a Dry-Stack is achieved by the mine (>84% Solids By Weight), several technologies are available to maintain the Dry-Stack. They vary from the use of “Geotubes” – “Zero Water Flux” and “Oxygen Limiters” to manage water balance. ENTER “1” if your mine uses 3 or MORE methods – ENTER “2” for 2 methods, and ENTER “3” if it relies on a sole method for Dry-Stacking.
- Total Region Area (TRA) - hectares (ha)
On paper, a mine is a singular legal entity, which in isolation may appear to only affect its immediate area. But when that mine is one of many within a region or watershed, it adds to the cumulative effect of mining in the Total Region Area. The Previous Impact Area is the sum total of all other developed areas in the Region (in hectares). This will produce a factor representative of the actual increase of a mine's impact on a Total Region relative to all other development in the region. This factor will increase the final total Impact Area Value (IAV) to produce the Grand Impact Area Value (GIAV). Therefore, a mine in a less- developed area will have a lower GIAV than a mine added to more highly-developed area.
- Water Bodies (WB) - hectares (ha)
Since the downstream effects of mining can run to infinity, this portion of the calculation is meant to reflect the sustained damage within a reasonable periphery of a mine. This factor tries to capture the portion of significant water bodies (rivers, lakes, wetlands) at risk of, or experiencing direct or indirect disturbance, discharge, or degradation within the Project Footprint, Project Impact Footprint, or downstream of the mine. In some instances, this may cover may tens, or even hundreds of square kilometres; in other case it may be confined within a smaller area. For rivers and streams, use the average width.