Tailings and waste rock: guide to reporting
This document will help facilities that need to report the disposal of tailings and waste rock to the National Pollutant Release Inventory (NPRI).
If your facility meets the reporting criteria, you are required to report the disposal of tailings and waste rock to the NPRI.
Sectors that dispose of tailings and waste rock may include, but are not limited to, coal, diamonds, potash, oil sands, metals (which include copper, nickel, lead, zinc, gold, silver, iron ore and uranium), quarries, industrial minerals and other applicable non-mining sectors.
Tailings are the waste material, which may or may not be mixed with water, that remains after processing ore, ore concentrate or mined materials to extract marketable components such as metals, minerals or bitumen. This waste material could include ground rock material, sand, clay, process chemicals or residual metals, minerals or bitumen, petroleum coke (petcoke), and sulphur.
Ore refers to a natural deposit in which at least one metal or mineral occurs in sufficient concentrations to make mining the material economically feasible. In addition to metal-bearing deposits, “ore” can also refer to a deposit that is a source of a non-metallic substance such as bitumen, coal, diamonds or sulphur.
Waste rock is rock that is removed in the mining process to provide access to the ore and that is not further processed during the reporting year.
If you owned or operated a facility as of December 31 for a given year, you may be required to report to the NPRI. Note that if operations at a facility are terminated during the calendar year, the last owner or operator of the facility is required to report.
If your facility meets the employee hour threshold (a total of 20,000 or more employee hours worked), you may be required to report on tailings and waste rock. See the Guide to reporting to the NPRI for more information.
Substances to report
Of the substances included in the NPRI, those listed in Parts 1A, 1B and 2 are the ones related to tailings and waste rock. You must consider the reporting criterion for each applicable Part 1A, 1B and/or Part 2 substance.
For Part 1A and 1B substances, you must consider those that are manufactured, processed, used or disposed of to tailings and/or waste rock management areas. Consideration of Part 2 substances is limited to the quantities released, disposed of, or transferred as a result of either incidental manufacture or the generation of tailings.
If your facility meets the employee hour threshold detailed above, as well as the substance-specific reporting criterion, you must report on that substance(s).
For substances contained in tailings, there is no minimum concentration threshold when considering Parts 1A, 1B and Part 2 substances.
In terms of waste rock, for Part 1A substances, the normal 1% by weight concentration threshold applies. For Part 1B and 2 substances, there is no minimum concentration threshold.
Keep in mind that the threshold calculation is not limited to the quantity of an NPRI substance found in tailings and waste rock. When determining if the reporting threshold is met for a substance, you are required to include all of your facility’s operations/processes in the calculation.
The key exclusions related to tailings and waste rock are outlined below and illustrated in Figures 1 through 3.
Quantities that are excluded from the mass reporting thresholds are also excluded from NPRI reporting.
The following exclusions only apply to substances contained in the materials below; that is, overburden, waste rock, tailings and product. Once the substance is released to air or surface waters from the materials below (for example, dust released while moving overburden or leaching of metals from tailings or waste rock), the quantity of the substance released must be included in the threshold calculations and reported to the NPRI if applicable.
Overburden is the unconsolidated materials overlying the ore (or bitumen) deposit, including, but not limited to, soil, glacial deposits, sand and sediment. This material is excluded from threshold calculations and reporting.
Figure 1 - Diagram of non-reportable material
The flow chart contains two rows of boxes.
The first row contains two boxes. The first is to identify overburden; the second is to identify product.
Down arrows from both boxes in the first row lead to a single box in the second row. This box signifies that neither overburden or product is to be reported.
In some cases, mining operations have operating permits that classify the waste rock generated by that facility. Where a valid operating permit specifically identifies waste rock as inert, the NPRI substances found in that waste rock are to be excluded from threshold calculations and reporting. It should be noted that the mining industry often refers to inert waste rock as “clean” waste rock.
Where there is not a valid operating permit that specifies that waste rock is considered inert, the exclusion is based on the following criteria in terms of sulphur content as well as acid-generating potential.
- Quantities of substances in waste rock are to be excluded if the waste rock has a sulphur content of less than or equal to 0.2 percent, or if it has a higher sulphur content but the ratio of neutralizing potential to acid-generating potential is greater than or equal to 3:1.
Regardless of the criteria above:
- Arsenic must be included in threshold calculations (and reported, if required) when the concentration of arsenic in the waste rock is greater than 12 mg of arsenic per kg of waste rock. Arsenic releases are not necessarily linked to acid-generation potential.
- Releases of all NPRI substances from waste rock are to be included in the threshold calculations (and reported as required).
Where a quantity of an NPRI substance in waste rock is excluded based on these factors, you are required to provide adequate information on the permit or other data on which the exclusion was based.
In certain situations, accumulated waste rock can be used as material for road construction or can be sold as construction aggregates. While this material was originally excluded from reporting, further processing of the material will need to be considered and reported if applicable.
Figure 2 - Diagram of reportable and non-reportable components of waste rock
The flow chart contains five rows of boxes.
The first row contains one box that reads “Waste Rock”. This box leads to one of two boxes in the second row with a down arrow. That box asks the following question: “Does it contain arsenic at concentrations > 12 mg/kg?”
If the answer is “Yes”, a right-facing arrow leads to a box that reads “Report arsenic”. If the answer is “No”, a down arrow leads to a box that asks the following question: “Is it inert?”
From the “Report Arsenic” box an arrow with the words “All other substances” also leads to the box that asks: “Is it inert?”
If the answer to the question “Is it inert?” is “Yes”, a right and down arrow leads to a box that reads “Do not report.”
If the answer the question “Is it inert?” is “No”, a down arrow leads to a box that asks the following question: “Is it used for roads, tailings dams or stope fill?” If the answer is “Yes”, a right-facing arrow leads to a box that reads “Do not report.”
If the answer is “No”, a down arrow leads to a box that reads: “Report disposals to waste rock management areas or to tailings management areas, as appropriate.”
The following documents can provide additional information on waste rock sampling techniques:
- Environment and Climate Change Canada (2009). “Environmental Code of Practice for Metal Mines 2009”, TD195 M5 E58 2009
- Natural Resources Canada (1994). “Handbook for Waste Rock Sampling Techniques”, June 1994
- Natural Resources Canada (1994). “Review of Waste Rock Sampling Techniques”, June 1994
- U.S. EPA (1999). “EPCRA Section 313 Industry Guidance - Metal Mining Facilities”, January 1999
Stable/inert constituents of tailings
Certain materials in tailings that are inert, inorganic and have not been crushed or otherwise physically or chemically altered, are excluded from threshold calculations and reporting (for example, sand grains from bitumen mines or in-situ production of bitumen).
This exclusion applies only to the components of the tailings that meet the criteria; any components in the tailings stream that do not meet the criteria have to be reported; provided the applicable threshold has been satisfied.
In some cases, tailings are used to fill in stopes or as pillars to provide support for the surrounding rock in an underground mine. The tailings material containing NPRI substances become part of the structure of the facility. As a result, the general exclusion for structural components of the facility applies and the NPRI substances found in the tailings used for underground fill are not reported.
At coal mining operations, both coarse and fine rejects can be formed as a result of washing operations. The resulting materials are considered to be tailings and not waste rock because, by definition, waste rock is not processed in any way.
Figure 3 - Diagram of reportable and non-reportable components of tailings
The flow chart contains four rows of boxes.
The first row contains one box that reads “Tailings”.
This box leads to one of two boxes in the second row with a down arrow. That box asks the following question: “Are portions inert, inorganic and not altered?”
If the answer is “Yes”, a right-facing arrow leads to a box that reads “Do not report those portions.” If the answer is “No”, a down arrow leads to a box that asks the following question: “Are they used for roads, tailings dams or stope fill?”
From the “Do not report those portions” box, an arrow with the words “All other portions” also leads to the box that asks “Are they used for roads, tailings dams or stope fills?”
If the answer to the question “Are they used for roads, tailings dams or stope fills?” is “Yes”, a right and down arrow leads to a box that reads “Do not report.”
If the answer to the question “Are they used for roads, tailings dams or stope fills?” is “No”, a down arrow leads to a box that reads: “Report disposals to tailings management areas.”
Reporting tailings and waste rock disposals
If, after considering the reporting criteria applicable to your facility, you determine that information on tailings and/or waste rock disposal is required to be included, you must report the following information:
- net quantity of the substance(s) being disposed on-site and/or off-site in the calendar year
- information on sampling concentrations with respect to the detection limit of the measurement method used
- actual detection limit for the measurement method used to generate the net quantity value
- average concentrations for the material entering the tailings and/or disposal management area
- details on any quantities excluded from the net quantities reported
Please note that net quantity is the final amount of NPRI substances that are either added or removed (to/from a waste rock or tailings management area) at the end of the applicable calendar year. For some facilities, the net quantity will be a positive value and for other facilities it will be a negative value. For this exercise, you do not need to account for the internal movement of waste materials if it is completed in the same type of management area. However, you do need to consider the quantities of “additions” and “removals” if the material is moved from a waste rock management area to a tailings management area or vice versa.
Cyanides, if used in the ore separation process, will need to be considered when you are determining the manufactured, processed or otherwise used thresholds. In some cases, cyanides are recovered from the tailings for re-use. Cyanides should be reported as the net quantity disposed at the tailings management area, regardless of the number of recovery processes that have taken place.
Note that the use of any acid listed on the NPRI must be considered when calculating if applicable NPRI thresholds are met. Acids that are neutralized prior to being disposed of in tailings and waste rock management areas should not be reported as being disposed of to tailings and/or waste rock.
Mines are closed when the ore minerals are completely exhausted or when it is no longer profitable to recover the minerals that remain. In some cases, mines may be closed temporarily and put into a status called “care and maintenance,” also known as temporary suspension. This is frequently done during periods of low commodity prices, with the expectation that higher prices in the future will make further commercial operations financially viable. Mines may still be required to report under this status. Eventually, ore reserves are depleted, and mines are permanently closed/decommissioned.
Decommissioned mines are normally expected to comply with the good practice of mine reclamation. Any NPRI substances that are associated with reclamation activities must be considered towards the applicable thresholds and reported as required.
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