page_title: Mount Polley mine
section_title: Breach and spill
hierarchical_section_title: Mount Polley mine / History / Breach and spill
caption_attribution_description: English: Mount Polley Mine site in British Columbia on July 24, 2014 prior to the dam breach on August 4, 2014
context_page_description: The Mount Polley mine is a Canadian gold and copper mine located in British Columbia near the towns of Williams Lake, and Likely. It consists of two open-pit sites with an underground mining component and is owned and operated by the Mount Polley Mining Corporation, a wholly owned subsidiary of Imperial Metals. In 2013, the mine produced an output of 38,501,165 pounds of copper, 45,823 ounces of gold, and 123,999 of silver. The mill commenced operations in 1997 and has a current mine life to 2026. The mining company owns 20,113 hectares of property near Quesnel Lake and Polley Lake where it has mining leases and operations on 2,007 hectares and mineral claims on 18,106 hectares. The processed ore is delivered by truck to the Port of Vancouver. The mine is on care and maintenance status until the price of gold, copper, and silver becomes more economically viable.
  As of March 2012, the estimated reserves of the mine were 87.3 million tonnes of 0.292% copper, 0.302 grams per tonne gold and 0.407 grams per tonne silver.
context_section_description: The Mount Polley mine's tailings facility experienced a dam breach and tailings spill that began 4 August 2014 releasing its water and slurry into Polley Lake. The spill flooded Polley Lake, creating a plug at Hazeltine Creek, and continued into nearby Quesnel Lake and Cariboo River. By 8 August the four-square-kilometre (1.5 sq mi) sized tailings pond had been emptied of the majority of supernatant (process water) that sits atop the settled crushed rock solids (mining waste, or 'tailings'). The slurry of tailings and process water carried felled trees, mud and debris and wore away the banks of Hazeltine Creek which flows out of Polley Lake and continued into the nearby Quesnel Lake. The spill emptied the tailings pond and caused Polley Lake to rise by 1.5 metres (4.9 ft), while also affecting Cariboo Creek and Quesnel Lake.  Remediation and reconstruction has been underway at the site since 2014. These efforts have included investigation on impacts to human health and safety and affected ecosystems while removing the tailings spill, reconstructing creek shorelines, installing fish habitats, and replanting trees and other local vegetation. Investigation by the remediation team showed elevated levels of selenium, arsenic and other metals consistent with historical tests before the dam breach. Initial reports had been concerned about the chemical impact of the tailings spill on the surrounding environment, but it was determined through subsequent investigation and remediation that the challenge posed by tailings spill was physical in nature.
  Tailings are the remainder of what remains after desired minerals have been removed. The Mount Polley Mining Corporation mined copper, gold, and silver from their mine at Mount Polley. The volcanic rock from which the desired minerals are extracted contains a mixture of orthoclase (36.95%), albite (24.38%), magnetite (7.38%), calcium plagioclase(7.12%), diopside (4.48%), garnet (3.33%), biotite (3.04%), epidote (2.12%), calcite (2.01%), chalcopyrite (0.17%), and pyrite (0.04%). The tailings at Mount Polley contain a usually low amount of chalcopyrite and a high amount of calcite, making them geochemically benign. A typical concern of the tailings of metal mining such as acid rock drainage does not occur at Mount Polley due to the unique distribution of compounds in the volcanic rock. The relatively high levels of calcite allow the mineral to act as a neutralizing agent for sulphides that are constituent in the chalcopyrite and pyrite. Therefore, the crushed rock tailings of Mount Polley are virtually inert, not reactive with air or water, instead having properties like natural sand.
  Early reactions to the tailings spill expressed grave concern.
  On August 6, two days after the breach, the British Columbia Ministry of Environment issued a Pollution Abatement Order to Mount Polley Mining Corporation. The company submitted an action plan for the Preliminary Environmental Impact Assessment, environmental monitoring, stopping the flow from the "Tailings Impoundment" breach, as required. The company was required and did report weekly on the implementation of action plan measures.
  A local state of emergency in nearby communities was initially declared in the interest of public safety with widespread water restrictions implemented and local equitable water distribution set up as a precautionary measure. Days later, water use restrictions were removed for area residents narrowing the "Do Not Use" order to only the impact zone directly affected by the breach, which included Polley Lake, Hazeltine Creek, and an area within 100 metres (330 ft) of the shoreline sediment deposit, where Hazeltine Creek runs into Quesnel Lake where the government advised that boiling water would not be sufficient. Initial tests at five testing sites of the second water test run indicated zinc levels above chronic exposure limits for aquatic life.
  All tourism businesses in the affected areas remained open. Because the affected water system is salmon-bearing, there was a temporary closure of part of the Chinook salmon fi
caption: 24 July 2014
exif: {}