MAGNA, Utah (AP) -- A major earthquake could cause a century-old copper tailings pond in Magna to fail and spill soupy waste across a state highway, according to a new engineering assessment.
The assessment by Colorado-based Tetra Tech said the slurry could travel 428 feet like a flash flood but that it would stop before hitting any houses.
"Really, the public-safety concern is the highway," said Troy Meyer, Tetra's lead engineer.
The report was commissioned by Kennecott Utah Copper Corp. to address safety questions at the tailings pond, which holds about 2 billion tons of waste across 14 square miles just north of Magna.
Kennecott said the findings indicate residents of Magna and a subdivision half a mile away have no reason to fear of being swept away if a dike fails.
The safety assessment was based on the possibility of a 7.25-magnitude earthquake.
Geologists say quakes that large hit the Salt Lake Valley about once every 1,350 years, but it's been nearly that long since the valley has seen one.
The tailings pile is dry on its top and sides, but wet enough in the center that it could run as a thick liquid. Kennecott said it's trying to drain water from the most saturated tailings.
The Colorado company discussed its findings this month at a community hearing. The full report is scheduled for release next month.
Sen. Brent Goodfellow, a West Valley City Democrat, said the report should put to rest any fears about the tailings pond.
Even so, Tetra Tech reported this summer that Kennecott has work to do to shore up the tailings pond. It said the company's goal to make the pile quake-proof by 2018 won't happen that early.
Engineers say the pond's south side, which faces Magna, is likely to meet minimum safety standards within seven years. Other dikes will take longer to shore up.
Salt Lake County Councilman Michael Jensen said the county will have to make certain no development creeps closer to the impoundment.
Information from: The Salt Lake Tribune
(Copyright 2009 by The Associated Press. All Rights Reserved.)