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).
Background
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.
Definitions
Tailings
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
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
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.
Reporting criteria
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.
It is important to remember that the quantity otherwise used includes all releases and disposals of an NPRI substance. Therefore, the NPRI substances that are released as fugitive emissions must be included in threshold calculation and for reporting. This might include the individual metals in the dust, as well as the dust itself as a reportable particulate. The stockpiles and exposed area wind erosion guidance and emission calculator maybe used to estimate the releases to air, due to wind erosion from exposed waste rock and tailing areas.
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).
Concentration thresholds
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.
Exclusions
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
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
Long descritpion
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.
Waste rock
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
Long description
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
Long description
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.
Mine closures
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
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.
Example calculations
Please note that these examples relate only to the waste rock and tailings disposal component of NPRI reporting requirements. You may also need to consider releases (to air, water and land), disposals and transfers for recycling of NPRI-listed substances from other sources at your facility.
Metal ore mine
Scenario
Each year, a metal ore mine produces 21 million tonnes of waste rock and 24 million tonnes of tailings. The sulphur content of the waste rock is 0.01%; the waste rock also contains 5 mg/kg of arsenic. The composition of the tailings is shown in Tables 1 and 2.
Waste rock
For this mine, the operating permits do not specifically address the classification of waste rock. However, the sulphur content of the waste rock is below 0.2% and the arsenic concentration is below 12 mg/kg. As a result, substances contained in this waste rock do not need to be included in calculations for the reporting threshold and do not have to be reported or for reporting.
Tailings
The tailings have been characterized for their metal content. The results are presented in the first row of data in Tables 1 and 2.
To determine the quantity of each Part 1A substance contained in the tailings, you multiply the concentration of each substance (in percent) by the total quantity of tailings disposed of during the year using the equation:
- Quantity of the substance in tailings (tonnes) = [24,000,000 tonnes tailings x concentration (%)] / 100
Once the quantities are calculated, you can compare them to the reporting threshold (10 tonnes) to determine the substances that you need to report. Table 1 lists the results for each substance.
| Substance | Silver | Chromium | Copper | Manganese | Nickel | Vanadium |
|---|---|---|---|---|---|---|
| Concentration (mg/kg) | 0.1 | 51 | 2.0 | 4500 | 2.5 | 9.0 |
| Concentration (%) | 0.00001 | 0.0051 | 0.0002 | 0.45 | 0.00025 | 0.0009 |
| Total mass of tailings | 24 million tonnes | |||||
| Quantity of substance in tailings (tonnes) | 2.4 | 1,224 | 48 | 108,000 | 60 | 216 |
| Threshold | 10 tonnes | |||||
| Quantity reportable to the NPRI (tonnes) | - | 1,224 | 48 | 108,000 | 60 | 216 |
To determine the quantity of each Part 1B substance contained in the tailings, you multiply the concentration of each substance (in percent) by the total quantity of tailings disposed of during the year using the equation:
- Quantity of the substance in tailings (kg) = ([24,000,000 tonnes tailings x concentration (%)] / 100) * 103 (kg/tonne)
Those substances with a less than sign (“<”) are below detection limits (with the detection limits shown in the table after the “<”). Where the concentration is below the detection limit, you use half the detection limit in your calculations.
Once the quantities are calculated, you compare them to the reporting threshold (varies by substance) to determine the substances that you need to report. Table 2 lists the results for each substance.
| Substance | Arsenic | Cadmium | Cobalt | Lead | Selenium |
|---|---|---|---|---|---|
| Concentration (mg/kg) | 5.7 | <0.1 | 7.6 | 0.4 | <0.5 |
| Concentration (%) | 0.00057 | <0.00001 | 0.00076 | 0.00004 | <0.00005 |
| Total mass of tailings | 24 million tonnes | ||||
| Quantity of substance in tailings (kg) | 136,800 | 1,200 | 182,400 | 9,600 | 6,000 |
| Threshold (kg) | 50 | 5 | 50 | 50 | 100 |
| Quantity reportable to the NPRI (kg) | 136,800 | 1,200 | 182,400 | 9,600 | 6,000 |
Reporting
The 24 million tonnes of tailings contain a total of 109,886 tonnes of NPRI Part 1A and 1B substances. Of these, only silver is below the mass reporting threshold; it does not need to be reported to the NPRI. You would need to report individual NPRI substance reports totalling 109,884 tonnes for disposal to the tailing management area.
Coal mine
Scenario
A coal mine generates 5 million tonnes per year of waste rock and 1 million tonnes per year of fine coal rejects (tailings). The sulphur content of the waste rock is 0.01%; the waste rock also contains 20 mg/kg of arsenic. The composition of the tailings is shown in Table 3.
Waste rock
The operating permits do not specifically address the classification of waste rock for this mine, but as the sulphur content of the waste rock is below 0.2%, reporting of most substances in the waste rock is not required.
Despite the sulphur content, since the arsenic concentration is above 12 mg/kg, the facility must include the quantity of arsenic in the waste rock in its calculations. You can determine the quantity of arsenic in the waste rock using the following equation:
- Quantity of arsenic in waste rock (kg) = (5,000,000 tonnes waste rock x concentration (mg/kg)] * 10-3
This gives a quantity of 100,000 kg of arsenic that must be reported as being disposed to the waste rock disposal area.
Tailings
The tailings (coarse coal rejects) have been characterized for their metal content. The results are presented in the first row of data in Table 3.
To determine the quantity of each substance contained in the tailings, you multiply the concentration of each substance (in percent) by the total quantity of tailings disposed of during the year using the following equations, as appropriate:
- Quantity of the substance in tailings (tonnes) = [1,000,000 tonnes tailings x concentration (%)] / 100
- Quantity of the substance in tailings (kg) = ([1,000,000 tonnes tailings x concentration (%)] / 100) * 103 (kg/tonne)
Once the quantities are calculated, you compare them to the reporting threshold for each substance to determine that substances you need to report. Table 3 lists the results by substance.
| Substance | Arsenic | Chromium | Cobalt | Copper | Mercury | Manganese | Nickel |
|---|---|---|---|---|---|---|---|
| Concentration (mg/kg) | 1.1 | 35 | 2.5 | 11 | 0.039 | 51 | 6.6 |
| Concentration (%) | 0.00011 | 0.0035 | 0.00025 | 0.0011 | 0.0000039 | 0.0051 | 0.00033 |
| Total mass of tailings | 1 million tonnes | ||||||
| Quantity of the substance in tailings | 1,100 kg | 35 tonnes | 2,500 kg | 11 tonnes | 39 kg | 51 tonnes | 6.6 tonnes |
| Threshold | 50 kg | 10 tonnes | 50 kg | 10 tonnes | 5 kg | 10 tonnes | 10 tonnes |
| Quantity reportable to the NPRI | 1,100 kg | 35 tonnes | 2,500 kg | 11 tonnes | 39 kg | 51 tonnes | - |
Summary
The 1 million tonnes of tailings contain 107.239 tonnes of NPRI-listed metals. Of these, all except nickel are above the mass reporting threshold. Therefore, you would have to report each of the quantities aside from nickel (100.639 tonnes total) as disposals to the tailing management area.
Oil sands mine
During the reporting year, an oil sands mine disposed of:
- 1.5 million tonnes of overburden
- 0 tonnes of waste rock
- 1 million tonnes of tailings
In this example:
- reporting on the substances in the overburden is not required (unconsolidated overburden is excluded from reporting)
- there is no waste rock to be considered
- unaltered constituents (for example, sand grains) of the tailings are excluded from reporting
- the remaining tailings contain quantities of NPRI-listed substances and these must be considered
Tailings
The concentrations of NPRI substances contained in the tailings have been measured. The results are presented in table 4.
To determine the quantity of each substance contained in the tailings, you multiply the concentration of each substance (in percent) by the total quantity of tailings disposed of during the year using the following equations, as appropriate:
- Quantity of the substance in tailings (tonnes) = [1,000,000 tonnes tailings x concentration (%)] / 100
- Quantity of the substance in tailings (kg) = ([1,000,000 tonnes tailings x concentration (%)] / 100) * 103 (kg/tonne)
Once the quantities are calculated, you compare them to the reporting threshold for each substance to determine the substances that you need to report. Table 4 lists the results by substance.
| Substance | Concentration (ppm) | Concentration (%) | Quantity of the substance in tailings | Threshold | Quantity reportable |
|---|---|---|---|---|---|
| Acenaphthylene | 0.02 | 0.00002 | 200 kg | 50 kg (total PAHs) | 200 kg |
| Ammonia | 65 | 0.065 | 650 tonnes | 10 tonnes | 650 tonnes |
| Arsenic | 5 | 0.005 | 50,000 kg | 50 kg | 50,000 kg |
| Benzene | 2.5 | 0.0025 | 25 tonnes | 10 tonnes | 25 tonnes |
| Benzo(a)anthracene | 0.1 | 0.0001 | 1,000 kg | 50 kg (total PAHs) | 1,000 kg |
| Benzo(a)phenanthrene | 0.002 | 0.000002 | 20 kg | 50 kg (total PAHs) | 20 kg |
| Benzo(a)pyrene | 0.055 | 0.000055 | 550 kg | 50 kg (total PAHs) | 550 kg |
| Benzo(b)fluoranthene | 0.01 | 0.00001 | 100 kg | 50 kg (total PAHs) | 100 kg |
| Benzo(e)pyrene | 0.1 | 0.0001 | 1,000 kg | 50 kg (total PAHs) | 1,000 kg |
| Benzo(g,h,i)perylene | 0.075 | 0.000075 | 750 kg | 50 kg (total PAHs) | 750 kg |
| Benzo(k)fluoranthene | 0.0015 | 0.0000015 | 15 kg | 50 kg (total PAHs) | 15 kg |
| Cadmium | 0.1 | 0.0001 | 1,000 kg | 5 kg | 1,000 kg |
| Chromium | 22.5 | 0.0225 | 225 tonnes | 10 tonnes | 225 tonnes |
| Cobalt | 0.01 | 0.00001 | 100 kg | 50 kg | 100 kg |
| Cadmium | 0.1 | 0.0001 | 1,000 kg | 5 kg | 1,000 kg |
| Copper | 10 | 0.01 | 100 tonnes | 10 tonnes | 100 tonnes |
| Dibenzo(a,h)anthracene | 0.011 | 0.000011 | 110 kg | 50 kg (total PAHs) | 110 kg |
| Ethylbenzene | 1.5 | 0.0015 | 15 tonnes | 10 tonnes | 15 tonnes |
| Fluoranthene | 0.1 | 0.0001 | 1,000 kg | 50 kg (total PAHs) | 1,000 kg |
| Fluorene | 0.075 | 0.000075 | 750 kg | 50 kg (total PAHs) | 750 kg |
| Indeno(1,2,3-c,d)pyrene | 0.05 | 0.00005 | 500 kg | 50 kg (total PAHs) | 500 kg |
| Lead | 1 | 0.001 | 10,000 kg | 50 kg | 10,000 kg |
| Manganese | 500 | 0.5 | 5,000 tonnes | 10 tonnes | 5,000 tonnes |
| Mercury | 0.0039 | 0.0000039 | 39 kg | 5 kg | 39 kg |
| Naphthalene | 0.3 | 0.0003 | 3 tonnes | 10 tonnes | - |
| n-Hexane | 15 | 0.015 | 150 tonnes | 10 tonnes | 150 tonnes |
| Nickel | 17.5 | 0.0175 | 175 tonnes | 10 tonnes | 175 tonnes |
| Perylene | 0.2 | 0.0002 | 2,000 kg | 50 kg (total PAHs) | 2,000 kg |
| Phenanthrene | 1 | 0.001 | 10,000 kg | 50 kg (total PAHs) | 10,000 kg |
| Phosphorous (total) | 200 | 0.2 | 2,000 tonnes | 10 tonnes | 2,000 tonnes |
| Pyrene | 0.5 | 0.0005 | 5,000 kg | 50 kg (total PAHs) | 5,000 kg |
| Quinoline | 0.05 | 0.00005 | 500 kg | 50 kg (total PAHs) | 500 kg |
| Selenium | 0.25 | 0.00025 | 2,500 kg | 100 kg | 2,500 kg |
| Toluene | 5 | 0.005 | 50 tonnes | 10 tonnes | 50 tonnes |
| Vanadium | 25 | 0.025 | 250 tonnes | 10 tonnes | 250 tonnes |
| Xylene | 10 | 0.01 | 100 tonnes | 10 tonnes | 100 tonnes |
| Zinc | 25 | 0.025 | 250 tonnes | 10 tonnes | 250 tonnes |
Summary
You would have to report on quantities of all substances except naphthalene as disposals to tailings management areas.
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