But a 1997 document the Tribune found shows what appears to be evidence of Kennecott's efforts to hide the seismic risk from Magna residents. That document states that Kennecott's land development arm went so far as to purchase 39 homes in Meadow Green Estates and then rent them and eventually sell them, all allegedly without disclosing the risk to tenants or buyers as Kennecott worked to fix the problems at the tailings pond.

Doughty said the mining industry is much more transparent these days and that such a risk discovered today would be reported immediately. "I think things would be very different today," she said.

As a result of Tribune's stories, Kennecott officials are preparing for possible questions from any concerned Magna residents at public meetings on Thursday and April 3, meetings that company spokesperson Kyle Bennett said Kennecott attends regularly.

Documents obtained by the Tribune dating back to 1997 and 1998 focus on how Kennecott handled the risk at the old, or south, impoundment that began operations in 1906 and received waste until 2001 when a new "seismically engineered, state-of-the-art" north impoundment was ready.

The 1997 document, marked "confidential attorney/client privileged communication," stated there had been at least two breaches in 1941 and 1964, attributed to "embankment failure" due to water intrusion. The communication, printed on Kennecott Utah Copper letterhead, also looks at past earthquakes in the Intermountain seismic belt, suggesting that as early as 1957 there was a concern about dam failure at the impoundment if a strong earthquake hit.

A 1988 study by a Canadian-based engineering firm, Klohn Leonoff, concluded that if a 7.5 magnitude earthquake struck there would be a 6 percent risk of impoundment failure at the "Magna Corner," or the southeast corner, of the impoundment within 30 years. What's the risk today?

"The risk is significantly less," Doughty said.

But the 1988 study prompted former Kennecott president Frank Joklik to create a task force to, among other things, look at reducing "risk of loss of life and serious bodily harm to the residents of Magna."

Kennecott put four years into an anticipated nine-year, $200 million upgrade that it abandoned "for reasons which are not clearly articulated in company records," attorney Ray Gardner wrote in the 1997 document. Joklik had also ordered Kennecott's land development arm to begin purchasing 200 homes in the Meadow Green Estates subdivision, the residential area considered most at risk if the Magna Corner failed.

"However, the Land Department was not expressly advised regarding the reasons for purchasing the homes, and management decided to conceal Kennecott's involvement in transactions through the use of an undisclosed agent," Gardner wrote in his memo to Kennecott officials.