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Guidance on the Reporting of Tailings and Waste Rock to the National Pollutant Release Inventory

Addendum (March, 2012)

This guidance deals with the following issues surrounding the required reporting of substances in tailings and waste rock (TWR) to the NPRI.

  1. Sampling and analysis requirements for the reporting of “reasonable” information
  2. Clarification as to when a “mine” is considered to be a “facility” subject to the reporting needs
  3. Specification of “reportable” tailings produced from oil sands mines
  4. Reporting considerations for “selenium” as a result of the reporting threshold changes for 2011

1. Sampling and Analysis Requirements

The Canada Gazette notice for NPRI specifies who must report and what must be reported on an annual basis. The facility owner/operator is required to provide the information which he/she possesses or may reasonably be expected to have access to, and should take reasonable steps to acquire the information to comply with the requirements set out in the Notice.

Mines often have many measurements available to them from their initial mineral exploration activities and from environmental impact studies required during the permitting process. Significant volumes of waste rock may be collected and analyzed during exploration and development in order to determine their acid generating potential. Once production starts, tailings are often measured to ensure effective process control. While these measurements may be conducted for non-NPRI purposes, they should nevertheless be evaluated to see whether they would provide the information required to comply with the NPRI notice. If the information is still missing, then “reasonable” steps must be taken to acquire sufficient information to comply with the Notice.

What is “reasonable” depends on the circumstances at each facility and should therefore be determined on a case by case basis. Generally, what is “reasonable” must take into account a number of factors including:

  • The size and complexity of the mining operation;
  • The likelihood of releases and the potentials for harm from the NPRI substances in the waste rock or tailings; and
  • The costs involved for any additional sampling and analysis to obtain the required information

Given the above considerations, an appropriate sampling and measurement plan should be in place and revised as appropriate as conditions change.

The sampling of waste rock and tailings represents a unique challenge since it involves many types and textures of wastes that are present at different types of disposal management areas (e.g. waste rock heaps in dry solid form, tailings piles in dry solid form, slurry tailings in ponds). Furthermore, there are relatively few standard reference methods available which describe the sampling techniques used to characterize the substances of interest in tailings and waste rock. The document cited below is perhaps the most appropriate and comprehensive reference source that can be referred to for TWR sampling:

A variety of analytical techniques are available for the geochemical analysis of mine wastes. The reference websites listed below provide further details on various analytical techniques that are used in the detection and quantification of the substances of interest in mine tailings and waste rock:

2. Clarification on the Definition of a “Mine” Subject to the Reporting Needs

A mining facility should be regarded as a “facility” for NPRI purposes once it is in the development phase (as shown in the Mining Sequence diagram in Figure 1) and construction of a pit or access ramps etc. have commenced.  During the development phase, large quantities of waste rock would be generated and the mines are expected to be able to readily obtain sufficient data on substances contained in waste rock for “reasonable” reporting as a result of the sampling and analysis activities required for the environmental assessment and permit approvals. 

Figure 1 - The Mining Sequence

See text on page for long description.

Long description: The mining sequence is divided into six stages. Consultation - communicate all actions and intentions with those who will be affected by mining sequence activities. Exploration - gather data about potential mineral deposits and acquire the rights to harvest those mineral deposits. Evaluation - determine which mineral deposit has the most profit potential. Development - construction of a mine or mines. Production - operation of the mine or mines. Closure - demolition of the mine or mines and rehabilitation of all lands used for mining.


For the purposes of NPRI, a mine would be defined as a “facility” for reporting needs if the mine is under development, in the production phase, or in the closure (decommissioning) phase.  Mine would also be considered a “facility” if it has been temporarily closed for economic reasons. Reporting of TWR information should therefore involve these types of mine, if the applicable reporting criteria are met.

3. The “Reportable” Tailings for Oil Sands Mines

Oil sands mining operations typically result into two streams of tailings as by-products: primary separation cell (PSC) tailings and froth cleaning tailings (see Figure 2).  The PSC tailings, known as the oil sands extraction tailings, account for the larger volume of the two tailings streams, while the tailings from froth cleaning (treatment) make up only about 2% to 4% of total oil sands tailings.  Both streams of tailings are normally discharged to a tailings pond (or tailings management facility) as process waste, where coarse solids settle quickly to be ultimately used in the construction of dykes and beaches, and fine solids settle very slowly to form fluid fine tailings which  eventually become MFT (mature fine tailings) over time.

The accumulated MFT can be sent to a large tailings dedicated disposal area (DDA) constructed at the oil sands mining site to facilitate the reclamation of the tailings.

The oil sands mining facility, for the purposes of NPRI reporting of the tailings disposal, should therefore not only consider the content deposited into the tailings pond, but also determine the volume and composition of the dry fines captured in the tailings DDA.

Figure 2 – Typical Activities of the Bitumen Mine Operations Phase
(Adapted from Oil Sands Tailings Technologies and Practice, AERI 2010)

Bitumen Mine Operations Phase, see text for long description

4. Reporting Considerations for Selenium under the New Reporting Thresholds

Previously, the mass reporting threshold for selenium and its compounds was 10 tonnes manufactured, processed or otherwise used.  Starting for the 2011 reporting year, the mass reporting threshold for this substance has been lowered to 100 kg. Since selenium is often associated with ores found in base metal mines, uranium mines, gold mines, and coal mines, this change is expected to increase the reporting of selenium by the mining sector.  Mining facilities would now be more likely to trigger the mass reporting threshold for selenium contained in the waste rock and tailings that are destined for disposal.

Previously, the quantity of selenium contained in waste rock at less than 1% was excluded from the threshold calculation, and from the reporting of disposals and transfers of waste rock. Starting for the 2011 reporting year, the quantity of selenium contained in waste rock must be considered for both the threshold calculation and the disposal calculation regardless of the concentration. The removal of the concentration criteria for selenium in waste rock might lead to the increase of selenium reports associated with waste rock disposals.

Like in the previous reporting years, the selenium contained in mine tailings would be included in the calculation of both the mass reporting threshold and the quantity of disposals regardless of concentration. The only difference for the reporting of selenium in tailings is the mass reporting threshold which has been lowered to 100 kg from the previous 10 tonnes. 

The following Table summarizes the major differences in the reporting criteria and reporting considerations for selenium and its compounds contained in waste rock and tailings between the pre-2011 and post-2010 reporting years:

Major Differences in reporting criteria and reporting considerations for selenium and its compounds
Criteria/ConsiderationsPre-2011 Reporting YearRY 2011 and Beyond
Mass Threshold10 tonnes100 kg
Concentration Threshold (by weight) for Selenium Contained in Waste Rock1% or greaterAny concentration
Concentration Threshold (by weight) for Selenium Contained in TailingsAny concentrationAny concentration
Reporting Considerations for Selenium Contained in Waste RockThreshold calculation and reporting of selenium in waste rock disposal are not required when the concentration of the substance is less than 1%.Threshold calculation and disposal reporting of selenium in waste rock are required regardless of the concentration, at the threshold of 100 kg.
Reporting Considerations for Selenium Contained in TailingsThreshold calculation and reporting of selenium in tailings disposal are required regardless of the concentration, at the threshold of 10 tonnesThreshold calculation and reporting of selenium in tailings disposal are required regardless of the concentration, at the threshold of 100 kg.

It should be noted that because of the threshold change, the selenium (6 tonnes) is now required to be reported in Example 1 per the following website link:

The statement result for the example should now be described as: Therefore, the individual substances totaling 109,884 tonnes (not 109,878 tonnes) would be reported for disposal to the tailings management area.

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