TAILINGS
Any compromises to the structural integrity of tailings storage facilities can pose significant environmental risks. With potential impacts to human health, the environment and the economy, tailings dam failures have triggered mining industry reviews and the development of new and revised standards.
New Gold’s Tailings Facilities
New Gold’s operating sites—New Afton and Rainy River—have a total of three active tailings facilities, in addition to an inactive tailings facility at New Afton. More information about these tailings facilities can be found in the table below.
Tailings Management at New Gold
New Gold’s tailings management practices include the following important features:
| FEATURE | DESCRIPTION |
|---|---|
| Design | The designs for New Gold’s tailings facilities are reviewed and updated throughout the construction and operations phases and include considerations for closure of each facility. The design of tailings facilities takes into account the climatic and ground conditions at each site. For example, our tailings facilities are designed to consider significant natural events, such as the probable maximum flood, so that the facilities are safe in the event of extreme weather or seismic events. |
| Financial security | Each site maintains financial security for the closure and post-closure monitoring of its tailings facilities. The financial security is based on approved closure plans, which are developed with stakeholder input. |
| Operations practices | Each site has an operations, maintenance and surveillance manual (OMS Manual), which sets out, among other things, how the site’s tailings facilities will be operated and maintained to ensure that they function in accordance with their respective design performance objectives, as well as regulatory and corporate policy obligations. |
| Risk assessments | Each site conducts regular risk reviews that include tailings-related risks, the key results of which are reported to corporate management at least annually. |
| Engineer of Record | Each site has appointed a qualified external professional engineer and their firm to be the Engineer of Record for its tailings facilities. |
| Surveillance technology | Sites use surveillance systems, such as piezometers, inclinometers, remote sensing and other technologies to monitor tailings dams and water levels. The OMS Manual sets out early-warning trigger and alert levels, facilitating early identification and management of potential dam stability concerns. |
| Inspections by employees | The Company’s tailings facilities are regularly inspected by trained New Gold employees—sometimes as frequently as several times a day. |
| Dam safety inspections | Formal dam safety inspections are conducted at least annually by the Engineer of Record. Recommendations made by the Engineer of Record are tracked to ensure follow-through by all employees. |
| Dam safety reviews | Each facility is subject to detailed third-party external dam safety reviews every five years, comprising a review of the design basis, construction and performance. |
| Independent reviews | The Company has an ITRB to provide independent, expert advice regarding the technical aspects of our tailings facilities. The ITRB meets at least twice per year to review information about tailings management practices at each facility. |
| Emergency preparedness | Each site has a detailed Emergency Response Plan, which is regularly reviewed and updated. The plans are also tested by employees to ensure response measures are effectiveand applicable. |
Tailings Facilities Details
| NEW AFTON MINE | RAINY RIVER MINE | |||
|---|---|---|---|---|
| NEW AFTON TAILINGS STORAGE FACILITY | POTHOOK PIT TAILINGS STORAGE FACILITY | HISTORIC AFTON TAILINGS STORAGE FACILITY | RAINY RIVER TAILINGS MANAGEMENT AREA | |
| Tailings Facility | New Afton Tailings Storage Facility (TSF) consists of 5 starter dams that have now joined into 1 continuous structure. All dams reached their ultimate height in 2021. | Pothook TSF consists of 1 dam. The TSF is primarily used for tailings deposition during upset mill conditions. | Historic Afton TSF consists of 2 dams. Construction ceased in 1991. |
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| Location |
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| Construction Method | Centreline construction | Downstream construction | Downstream construction | Centreline raise for the TMA perimeter dams, which include TMA South Dam, TMA West Dam and TMA North Dam |
| Design Standard | CDA’s Dam Safety Guidelines | CDA’s Dam Safety Guidelines | CDA’s Dam Safety Guidelines | CDA’s Dam Safety Guidelines (2013), Ontario Mining Association |
| Status | Active | Active | Care and maintenance |
|
| Current Maximum Height | 56m | 10m | 70m | 20.5m at South Dam |
| Current Storage Impoundment Volume | 30.5 million m³ | 2.55 million m³ | 27 million m³ | 25.8 million m³ (excluding pond volume) |
| Most recent dam safety inspection | October 2021 | October 2021 | October 2021 | August 2020 |
| Most recent dam safety review | 2017 | 2017 | 2018 | 2021 |
| Most Recent ITRB Review | November 2021 | November 2021 | November 2021 | October 2021 |
| Hazard potential 1, 2 | Risk rating of Extreme1 | Risk rating of Very High1 | Risk rating of Extreme1 | The TMA Dams (North, West and South) classified as Very High2 |
1 In accordance with CDA Dam Safety Guidelines, Table 2-1 Dam Classification. Dam classification considers the risks posed by the structures, such as the population at risk and incremental losses—loss of life, environmental and cultural values, and infrastructure and economics.
2 Using the Ontario Lakes and Rivers Improvement Act (LRIA) “Classification and inflow design flood criteria.” This is generally equivalent to a CDA consequence of Extreme.
MAC TSM Tailings Management Protocol Indicators
In 2021, New Afton achieved AAA scores on all five indicators of the Protocol and Rainy River reported level A on two of the five indicators through its 2020 self-assessment.
New Afton Thickened Tailings Technology
Our New Afton Mine is located in a semi-arid climate where annual evaporation rates typically exceed precipitation. As a result, traditional mine water recycling is challenging due to significant evaporated losses and is supplemented with a draw from Kamloops Lake. To mitigate this inefficiency, our team proposed the use of thickened tailings technology and completed a field scale pilot project in 2018. This technology allows immediate dewatering of tailings through a thickener and direct circulation to the mill to reduce tailings pore water and evaporative losses. In 2021, the mine continued to see progress on the construction of its Thickened and Amended Tailings (TAT) Plant, which will allow us to transition away from conventional slurry tailings.