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From tower to rubble: Former Key Bank building falls Saturday as part of Downtown Rising

Downtown may be rising, but first a part of it must collapse.

Early Saturday, as most Utahns enjoy their weekends sleeping late in quiet bedrooms, some 36,000 tons of concrete, steel and glass will come crashing down at the heart of the Downtown Rising revitalization project.

If all goes according to plan — and lightning is about the only thing that could stop it — the old Key Bank tower, 50 S. Main, will become the first Salt Lake City building to be imploded in nearly 25 years. It's coming down to make way for The Church of Jesus Christ of Latter-day Saints' City Creek Center development, which is on schedule for a mid-2011 opening.

And while much of the city is abuzz about the pending dramatics, certain to be a spectacle for anyone who manages to find a vantage point for the 6:45 a.m. show, construction officials want to drive this point home: It's an implosion, not an explosion.

"By all stretches of the imagination we're not blowing up the building," said Doug Loizeaux, vice president of Controlled Demolition Inc., which is managing the implosion.

In fact, it's not even a true implosion, which occurs when interior pressure is lower than external pressure and a building is crushed from the outside. Instead, the 20-story building is simply going to fall in on itself — with the help of some explosives.

It's not a whole lot of explosives considering the size of the building: only 180 pounds of it, mostly RDX inside extruded copper bars, which means each pound of explosive will take down about 200 tons of material.

"That's a lot of bang for your buck," Loizeaux said.

Crews have notched internal support columns on the building's fourth, seventh, 10th, 15th and 18th floors to weaken them. On Saturday, explosives will be placed at key points in the tower's basement, second floor and 10th floor, at nine spots on each floor.

When those explosives are detonated — in a southwest-to-northeast sequence — they will take out support beams, leaving the compromised columns with too much weight to bear, and the building will come tumbling down.

Loizeaux estimates about 90 percent of the building will end up in a 35- to 40-foot heap on the building's footprint, although crews hope to direct the collapse slightly to the southwest.

"The building wants to come down," Loizeaux said, noting that gravity will be the driving force behind the collapse. "It wants to come straight down."

But as controlled as the implosion will be — and officials say it's a very controlled process — there are always variables that could make for a dangerous situation. After all, a 290-foot building is falling to the ground in 16 seconds.

So, police will cordon off the surrounding area — from North Temple to 200 South between State Street and 200 West — starting at 1:30 a.m. Saturday. It won't open again until the dust has settled and it is deemed safe, which could be as little as 30 minutes or as long as four hours after the implosion.

Would-be viewers are being asked to stay home and watch television coverage of the implosion. There will be no public viewing area set up by City Creek Center officials or construction crews.

But the interest has some destruction junkies, history buffs and others doing what they can to get a front-row seat. Hotels, including some inside the implosion's impact zone, report they have booked several guests who hope to watch the collapse from their windows.

"We've had a few people do that, mostly local people," said Shila Ghramm, front office manager at the Salt Lake Plaza Hotel, 122 W. South Temple. She said the hotel is fully booked for Friday night.

Both the Plaza and the Downtown Marriott, 75 S. West Temple, are inside the area that police will shut down early Saturday, meaning anyone coming or going will have to plan ahead. After the roads are closed at 1:30 a.m., hotel guests will be allowed in by police. But from 5:45 a.m. to 7:45 a.m., no one will be allowed to enter or exit any hotel.

Before the implosion, crews will check surrounding buildings for existing structural damage so they can be checked for implosion-caused damage later. But Loizeaux said there shouldn't be a lot of ground vibration from the collapse.

Ventilation systems in surrounding buildings will be sealed off, so the Plaza will have no air conditioning for a good chunk of Saturday morning. The Marriott recycles internal air so air conditioning should not be affected.

The implosion will kick up a cloud of dust, mostly silica, as asbestos and other harmful materials have been removed. But because of the heavy particles that will be flying through the air, there is some health risk.

But outside the impact zone, there shouldn't be much effect on the rest of downtown. The Farmers Market at Pioneer Park will go on as scheduled. After the implosion, crews will get to work cleaning up dust, with their top priorities to get the TRAX light-rail trains up and running and to reopen Temple Square for people with weddings planned that day.

Grant Thomas, a spokesman for City Creek Center, said the implosion marks a "milestone" for the project. It is the last building to be demolished on the former Crossroads Plaza block. Demolition has started on the ZCMI Center block, and Thomas expects all the buildings coming down on that block to be gone within a year.

No other buildings will be imploded for the City Creek Center project. Key Bank is being imploded because it was deemed to be the safest, quickest way to take down the building. Other types of demolition would have meant months of traffic snarls and constant dust in the air.

"I, for one, am looking forward to having this part of this adventure over," Okland Construction superintendent Dave Kasteler said.

The last implosion in Salt Lake City was the Hotel Newhouse, which Controlled Demolition imploded in 1983.