Knight Piésold, Ltd., the engineering firm that designed the Mount Polley mine tailings dam that collapsed last August in British Columbia, failed to properly analyze the strength of the dam’s foundation when it designed the tailings facility, a provincial-sponsored report released Friday concludes.
Knight Piésold also did important testing as a subcontractor on the much touted dry stack tailings facility for the proposed Rosemont mine in southern Arizona.
The Independent Expert Engineering Investigation and Review Panel Report on the Mount Polley Tailings Storage Facility Breach “concluded that the dominant contribution to the failure resides in the design,” according to a media briefing.
Knight Piésold’s design did not account for the presence of a glacial lake deposit beneath the tailings dam foundation, the Vancouver Sun reported.
Knight Piésold has not responded to numerous calls from the media seeking comment, nor has the company posted anything on its website as of Tuesday. The company issued a statement four days after the Aug. 4 collapse of the Mount Polley dam stating that it had turned over all responsibility for the dam in 2011 to AMEC Earth and Environmental.
AMEC designed the proposed Rosemont mine’s “dry stack” tailings waste dump and used Knight Piésold as a subcontractor to conduct tests. The firms role at Rosemont raises questions over the stability of what would become the largest dry stack tailings dump in the world.
AMEC prepared the final design report for Rosemont’s dry stack tailings storage facility in April 2009. AMEC hired Knight Piésold to conduct laboratory testing on materials that would be used in Rosemont’s proposed tailings facility.
AMEC also turned to Knight Piésold in 2010 to undertake an analysis of soil materials that would be used in the Rosemont tailings facility in response to a request for additional information from the Arizona Department of Environmental Quality.
ADEQ raised concerns over the design of Rosemont’s tailing facility in an April 14, 2010 letter to the Rosemont Copper Company. ADEQ requested additional testing after it determined that the previous “assessment of physical and engineering properties of the dry stack tailings…is inadequate.”
ADEQ was particularly concerned about the possible impact of shallow ground water on the stability of the tailings dump.
“The central portion of the Dry Stack Tailings appears to be situated just above the ground water level,” ADEQ stated. The state agency asked Rosemont to provide additional data to show how the shallow groundwater table would effect the “structural integrity of the tailings pile.”
The use of so-called dry stack tailings facilities is a relatively new technology that uses filters to reduce the amount of moisture in the slurry of mine waste created by the milling process. Rosemont is proposing to use the dry stack facility to save water and reduce the “footprint” of the tailings because they can be compacted.
In Canada, Reuters is reporting the British Columbia government probe found that the breach at Imperial Metal’s Mount Polley mine, which sent billions of gallons of wastewater and sludge into waterways, happened because the dam’s weight was too much for the foundation to bear.
“The design did not take into account the complexity of the sub-glacial and pre-glacial geological environment associated with the perimeter embankment foundation,” the panel’s chair, Norbert Morgenstern, said after the 5-1/2-month investigation.
Morgenstern said design flaws created a “loaded gun” and the construction of the steep dam perimeter embankment slopes “pulled the trigger.”
A second report from B.C.’s chief inspector of mines will look at who should take the blame for the massive breach, but Jack Caldwell, a leading North American expert in the field of tailings dams, told the CBC that it’s clear that key questions remain unanswered.
Caldwell, who has more than 40 years’ experience, questions why the tailings pond was built atop unstable ground in the first place — and indicated a perfect storm of little problems led to the massive breach at Mount Polley.
The Toronto Globe and Mail posted a timeline of key actions at Mount Polley that shows engineers knew the tailings dam was being constructed in an area where unstable post-glacial soils were present. Knight Piésold stated the softer deposits were isolated and would not affect dam stability.
Bloomberg is reporting mining-waste spills will continue to occur in British Columbia unless government and industry enforce higher safety and design standards.
If the number of active tailings ponds in the Canadian province remains unchanged, and their performance in the future reflects the past, then on average there will be two dam failures every 10 years, the three-member engineering review panel said in the 147-page report.
“In the face of these prospects, the panel firmly rejects any notion that business as usual can continue,” the investigators said.
The prospect of more tailings dam failures comes at the same time British Columbia is moving forward with the approval of new mining projects, some of which are on important waterways that contribute to Alaska’s salmon fisheries, SeattlePI.com reports.
“The Mt. Polley disaster is a stark example of B.C.’s stewardship of a project that the government and the developer claimed was safe,” said Mark Jensen, mayor of the Petersburg Borough. Petersburg is a major fishing center in southeast Alaska.
“We can’t let a similar accident taint the rivers of the transboundary region along the border between northwest B.C. and Southeast Alaska,” Jensen said according to SeattlePI.com.
The Mount Polley tailings dam failure was followed three days later by the collapse of a tailings dam at the Buenavista del Cobre mine in Cananea, Sonora. That failure dumped 40 million liters of copper sulfate into the Rio Sonora. Mexican authorities blamed the mine’s owners, Southern Copper Corp., a subsidiary of Grupo México.
Copper Investing News opined that the dam failures are “a reminder of why lengthy permitting and environmental approval processes are necessary for mine construction, and of why due diligence should always be an ongoing process for investors.
“With multiple stakeholders involved and social license issues coming to the forefront for mining projects, it’s more important than ever for investors to find evidence that companies are environmentally and socially aware.”
As a Professor Emeritus of Physical Geography and Weather and Climate, I think that Hudbay’s motto should be “Oh Holy money, profit is truly your name.”.
THE MOUNT POLLEY TAILINGS SAGA GROWS MORE SINISTER WITH EACH PASSING DAY . THE RCMP HAVE NOW RAIDED THE OFFICES OF IMPERIAL METALS , BOTH IN VANCOUVER AND AT THE MINE SITE , IN SEARCH OF MORE INFORMATION THAT HAS ELUDED THE INVESTIGATION TO DATE . IN THE CASE OF THE ROSEMONT COPPER PROJECT , DID AUGUSTA MAKE ” ALL ” OF THE TECHNICAL RECORDS AVAILABLE TO HUDBAY BEFORE THEY STARTED SHREDDING ?
ENGINEERING CONSULTANTS , SUB-CONTRACTORS , GOVERNMENT AGENCIES AND MANAGEMENT ALIKE HAVE A LOT TO ANSWER FOR IN THE CASE OF MOUNT POLLEY . TO SAY THAT ” HUMAN ERROR ” IS NOT A FACTOR IS HIGHLY DOUBTED AT BEST . IT ALL GOES BACK TO THE ORIGINAL ” MINE PLAN ” AND WHO IN GOVERNMENT SIGNED OFF ON IT , ALLOWING THE COMPANY TO PROCEED AS IT DID . THE ROSEMONT MINE PLAN HAS BEEN QUESTIONED AS TO ITS ADEQUACY AND PROBABLY FOR GOOD REASON . HUDBAY SHOULD HAVE REASON TO BE CONCERNED OVER THE PERMITTING OF THE ROSEMONT PROJECT . MORE WORK ON THE ” TAILINGS ” DISPOSAL PROPOSED FOR ROSEMONT WOULD APPEAR TO BE IN ORDER .
THE ENTIRE ISSUE OF ” TAILINGS ” HAS SPREAD ACROSS CANADA AND BEYOND . THE USE OF ” DRY STACKED TAILINGS ” IS GAINING MOMENTUM BUT THERE ARE VERY FEW CASES TO REFER TO . THE PRESS HAS REFERRED TO ONE IN ALASKA AND ONE IN MEXICO . THE COST FACTOR IS OMINOUS BUT THE ENVIRONMENTAL BENEFITS , IN PRINCIPAL , WOULD BE WORTH IT SHOULD HUDBAY GO AHEAD WITH ROSEMONT .
THE MINING INDUSTRY HAS A HISTORY OF LEAVING BEHIND AN ENVIRONMENTAL NIGHTMARE WHEN IT MOVES ON . GOVERNMENT AND TAX PAYERS ARE LEFT TO BURDEN THE MAJOR COST OF RECLAMATION , MUCH OF WHICH IS SIMPLY NEVER CARRIED OUT . THE ROSEMONT COPPER PROJECT SHOULD BE BONDED FOR AT LEAST US$500 MILLION TO COVER ENVIRONMENTAL/POLLUTION/RECLAMATION ISSUES DURING THE LIFE OF THE MINE AND BEYOND .
It is interesting to note, that one of the purposes of the Report on the Mount Polley Failure was to make recommendations of how Best Available Technology (BAT) could be used reduce the number of tailings dams that might be subject to failure. This report specifically cites the use of “dry stack” tailings as the best method to achieve this goal. Rosemont Copper is currently pursuing this option.
Rosemont is planned for just above the shallow water table. We just had a 2 inch rain-probably more than that in the Santa Rita’s. What did that do to the water table and was it factored into the design? I believe the underlying rock is a brecia that is more difficult to move than a glacial till, but it still can move.
It is interesting that the opening paragraph of your article states that “a provincial-sponsored report placed the blame for the Mount Polley tailings dam failure on Knight Piésold, Ltd.
However, no such statement was made in this study. In fact, the panel that wrote the Mount Polley report made it very clear that this investigation did not express “any conclusions or recommendations regarding the potential civil or criminal liability of any person or organization.”
Rosemont Mine Truth’s decision to publicly blame Knight Piésold, Ltd. for the tailings dam failure at Mount Polley has nothing to do with events that are taking place in British Columbia. Nor, do they have any interest in learning the truth about what really happened at Mount Polley. Distorted facts contained in this article are solely designed to mislead the public about Rosemont Copper’s efforts to develop a 21st century mining project.
Chis–What are your credentials? Who do you work for?