As long as the weather cooperates, construction crews are ready to go ahead with Salt Lake City's first implosion in nearly 25 years on Saturday.

As part of the demolition work to make way for The Church of Jesus Christ of Latter-day Saints' City Creek Center, crews with Okland Construction will implode the former Key Bank tower, 50 S. Main, early Saturday, the first implosion in the capital city since the Hotel Newhouse fell in 1983.

Okland received its final city permits for the implosion Tuesday morning.

"As far as the city is concerned the demolition by implosion is approved," city building official Orion Goff said. Crews received the go-ahead from the state Air Quality Board in May and has since met other approvals, including from Rocky Mountain Power and Questar Gas.

The building's implosion is planned for about 6:30 a.m. Saturday, and state, city and construction officials are asking would-be observers to stay home and watch the blast on TV.

The state Division of Air Quality, according to a statement, "strongly encourages people to avoid the downtown area 6:30 Saturday morning when the Key Bank Tower is schedule to implode, shooting a cloud of dust in the sky."

Crews expect a cloud of dust to rise above the implosion site. It should settle within about 20 minutes, although crews could be cleaning dust from the surrounding area for up to four hours after the implosion.

Beginning at 1:30 a.m. Saturday, roads around the demolition site will close and won't reopen until 10:30 a.m. The closures include South Temple, 100 South, West Temple, Main and Regent Street between 200 West and State and from North Temple to 200 South.

Buildings on the same block as the office tower will be evacuated, with the exception of the Marriott Hotel.

"Worker safety, combined with cost and time savings, make implosion the preferred method of demolition," City Creek Center spokesman Dale Bills said of the plans in May. "Implosion also limits public inconvenience to one day, as opposed to four to five months."

Buildings are imploded by strategically placed explosions within the building. Those explosions take out key pieces of the building in a way that causes the upper levels to fall inward, so the building collapses on its own footprint and doesn't impact neighboring buildings.

City Creek Center is a proposed 20-acre mixed-use development that will replace the Crossroads and ZCMI Center malls with an indoor-outdoor mix of retail, residential and office space. The new development is set to open in 2011.

Construction crews have been bringing down buildings on the Crossroads block for several months, beginning with the Inn at Temple Square and moving toward the southeast. Those buildings and parking structures have come down with crews and heavy machinery knocking them down wall by wall, piece by piece.

The Key Bank tower will be the last building on the block to come down and the only implosion required for the project. The Marriott Hotel, Gateway Tower West and the Crandall and McIntyre retail buildings will remain standing on the block.

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E-mail: dsmeath@desnews.com