Magna safe from tailings

Fears that a monster earthquake could loose a deadly wall of liquefied earth and mine tailings on residents of Magna were addressed, and tentatively allayed, by preliminary findings of an independent study released Monday.

Kennecott Utah Mining Corp. has been under the gun since last March when internal memos were uncovered indicating that the company became aware — in 1988 — of earthquake-related risks to residents near an enormous, 5,700-acre tailings impoundment north of Magna, but made no effort to communicate those risks. After a series of public meetings on the issue last year, Salt Lake County formed a 19-member committee to administer an independent study, financed by Kennecott, of exactly what could happen in the event of a large-scale seismic incident.

A representative from Tetra Tech, an engineering research company based in Golden, Colo., that was hired to do the evaluation, told the committee Monday that while a 7.25 magnitude earthquake would likely lead to breaches in the earthen walls on the south and east sides of the containment structure (roughly bordered by 2100 South and 8000 West) the "run out" of liquefied material would likely not reach anywhere near residences. It would, however, travel far enough, on the south side, to put a stretch of state Route 201 (2100 South) under a fast-moving river of sludge.

"It really is like a flash flood," said Troy Meyer, a Tetra Tech engineer. "They're violent and intense and it's like a tsunami coming at you. I'd say it would hit the highway in five seconds."

Salt Lake County Councilman and Unified Fire Authority Chief Michael Jensen said Kennecott has already provided for the installation of a warning-light system on arterial roads leading to the highway, but there is currently nothing to warn drivers already on 2100 South.

"These are preliminary findings and we'll wait for a final report, but we'll certainly be looking at safeguards, including some kind of system on the 201," Jensen said.

Meyer said on the east side of the impoundment, the run out would dissipate long before reaching any existing roads or structures. In the event of a smaller earthquake of 6.5 magnitude, the modeling shows no failure on the south side, but a similar (about 300 feet) run out distance on the east side.

The Tetra Tech findings are similar to those in previous Kennecott studies of the issue, though Meyer said his company uncovered some "data gaps" and has notified Kennecott that ongoing monitoring, with enhancements in some areas, will ensure that changing conditions at the site do not alter estimates. Meyer said Kennecott had committed to the changes and continuing to gather data that would increase the accuracy of estimates, which, even using the best techniques available, were approximations.

In a statement released Monday afternoon, Kennecott officials offered recognition of dubious past conduct and expressed satisfaction that the Tetra Tech findings confirmed previous efforts.

"We are sorry that KUC's activities two decades ago cast doubt on our integrity," the statement reads. "We are pleased there is now conclusive, third-party information available regarding the safety of KUC's South Tailings Impoundment. Both … studies support the conclusions that homes in Magna would not be at risk due to a tailings impoundment failure during a significant seismic event."

A final version of the Tetra Tech report is scheduled to be presented to the study committee in about two weeks.

e-mail: araymond@desnews.com