In 2012

Salmo-area dam failure would have ‘very high’ consequences

A review of the HB mine tailings dam south of Salmo concludes the potential consequences of a failure should be reclassified as “very high.”

A safety review of the HB mine tailings dam south of Salmo concludes the potential consequences of a failure should be reclassified as “very high” based on Canadian dam safety guidelines.

The worst-case scenario report by Kelowna consultant Tetra Tech EBA released last week suggests that if the earthen dam breached, three people could die and clean-up costs could be in the tens of millions of dollars. The affected area would be less than one square kilometer but includes one home and Highway 3.

While there is no solid information on the total tailings volume of the dam, the consultant estimated it at 1.8 million cubic meters, and guessed about 40 per cent, or 714,000 cubic meters, would be released in the event of a failure. Flood levels could reach several meters with a potential loss of lives and the highway would be covered with mud and debris and likely closed three to four weeks.

The cost of cleaning up the tailings, restoring contaminated land, and rebuilding the dam is estimated at anywhere from $45.7 million to $89.4 million. The consultant said the wide range was due to costs being “highly sensitive to haulage distances, levels of restoration and material availability.”

In the last safety review of the HB tailings dam in 2002, the consequences of a failure were rated “low” based on 1999 guidelines established by the Canadian Dam Association. That equated to “significant” under new guidelines adopted in 2007, suggesting that if the dam failed, there would be no fatalities and only limited economic and environmental damage. The five categories on the scale are low, significant, high, very high, and extreme.

Uli Wolf, the regional district’s environmental services manager, attributed the more dire conclusions reached by the latest report to different methodology around vegetation, soil, and water permeation, plus the use of more localized precipitation data.

Wolf said it’s up to the Ministry of Energy and Mines to approve the dam’s higher consequence rating, although he expects it to be a formality. The result will be more frequent inspections and reviews as well as higher capital costs for remediation.

The consultant’s report is subject to a third-party review, required by a ministry order in the wake of the Mount Polley tailings pond disaster, although Wolf said it is mainly intended to check for underestimated risk.

“Dams certainly have received a higher level of attention from the general public since the Mount Polley incident,” he said. “Maybe rightfully so. For us that comes with added cost and work to our department. We will have address that in future budgets.”

The latest report doesn’t specifically address the likelihood of a complete dam failure but makes several recommendations including conducting an emergency exercise of RDCK staff involved in the dam’s maintenance and an engineering study to assess ways of reducing the risk of internal erosion. Wolf said some action has already been taken on reconfiguring the spillway and further construction is expected.

Cominco (now Teck) built the dam in 1955 to store lead and zinc mine tailings and operated it from 1955-66 and 1974-78. The company sold the property in 1981 and the Regional District of Central Kootenay acquired it for landfill purposes in 1998, paying $650,000 more for the site than the previous owner, a Panamanian company that bought it only a year earlier.

In the early summer of 2012, a sinkhole formed on the dam following heavy rain. The regional district spent more than $800,000 stabilizing and reconstructing the dam, which it billed to the province. Recently, the regional district filed a notice of claim against Teck, seeking reimbursement for ongoing remediation work.

The cost of failure

If the HB tailings pond failed, a consultant estimates that it would deposit 714,000 cubic meters of material over less than one square kilometer. This is the predicted cost of cleaning up the mess:

Removal of mud/tailings debris to secure landfill: $28.6 to $57.1 million

Restoration of impacted area: $13.1 to $26.2 million

Replacement of dam: $4 to $6 million

Total direct economic losses: $45.7 to $89.4 million*

* Actually given as $83.4 million in the report, due to an adding error

Source: Dam Safety Review of HB Mine Tailings Storage Facility, Salmo, Tetra Tech EBA Inc., May 2014

Just Posted

Nelson firefighter wage negotiations in year six

Firefighting is an essential service, so strikes are illegal

EcoSociety asks city to become 100 per cent renewable

The plan would have Nelson ditch fossil fuels by 2050

Finding support at Community Connect

The 10th annual event offered free services, clothing and food on Saturday

RDCK calls for reversal of Sinixt extinction

The board opposed a land transfer to the Westbank First Nation this week

Nelson city council to update banner policy

Council will revisit the wording of the policy at its December meeting

RDCK holds open house on proposed boat launch

RDCK hosted an open house at Blewett Elementary to discuss plans for a boat launch at Taghum Beach

LVR Bombers volleyball team off to provincials

The senior girls’ squad secured a spot with a win over Trail last week

Winter kicks off in Nelson

Over 30 events are set to celebrate the snowy season

Man pleads guilty to Leafs recycling depot theft

Dezmond Waggoner had been charged with theft over $5,000

BC Transit buses to get safety door for drivers

These new full-length doors will be tested in Victoria, Kelowna and Abbotsford

Most Read