Kennecott Utah Copper Corp. still has decades of cleanup to do, but it now looks like a large area in the southwest portion of the Salt Lake Valley won't be put on a federal list of sites that are considered to be the most polluted in the country.

Kennecott officials said Monday they expect the Environmental Protection Agency next week to announce that several areas collectively known as the Kennecott South Zone will be taken off an EPA list of proposed Superfund sites. The South Zone site impacts communities like West Jordan, South Jordan, Riverton, Herriman and Copperton.

"It's a pretty big thing for all of us," Kennecott President Andrew Harding said during a meeting Monday with the Deseret News editorial board.

Being formally listed as a Superfund site is generally viewed as a stigma because contamination in such an area is so bad that the feds decide to step in and take on authority over cleanup efforts. Contaminants include lead, arsenic and selenium, which if exposed to at high enough levels over a long period have been linked to certain types of cancer, high blood pressure and gastrointestinal disorders.

Since about 1991 Rio Tinto, which owns Kennecott, has spent about $400 million on cleaning up mining waste that predates Kennecott's involvement in mining the Oquirrhs in the early 1900s. Over 25 million tons of mining waste have been removed from the surface in the South Zone.

In 1994 the EPA put Kennecott's South Zone and a North Zone, a site near Magna, on a list of proposed Superfund sites. In 1995 Kennecott, EPA and the state struck a cleanup agreement that has kept the sites from being formally listed as Superfund sites. Within the next few years Kennecott hopes the North Zone will also be off the list of proposed sites.

"It allows you to concentrate on moving forward with plans for the future," Harding said about shedding even a proposed Superfund label.

Those plans include huge residential developments on the west side of the Salt Lake Valley as Rio Tinto in Utah transitions away from its historic marker as mining giant.

But there are still sulfates and heavy metals in groundwater on the west side that Kennecott is cleaning up.

"It's going to be a decades long process," said Kelly Payne, principal advisor over closure and remediation for Kennecott.