Intro to implosion

Back in September 1963, just months before the assassination of President Kennedy and the rise of Beatlemania would consume the nation, college students at the University of Nebraska-Lincoln were settling into the newly opened Cather and Pound Halls for the first time.

More than 54 years later, the university’s oldest high-rise residence hall complex was imploded on Dec. 22, 2017, in favor of the campus’ newer suite-style housing that has been built in recent years.

While the university had been planning the demolition of the 13-story structures for several years, Tulsa, Oklahoma-based Ark Wrecking wasn’t named as the project’s demolition contractor until May 2017. Ark Wrecking, which has been in the demolition business since 1950, subcontracted the implosion preparations and execution to Phoenix, Maryland-based Controlled Demolition Inc. (CDI).

The decision to implode the building was made by the university, which wanted to limit the risk associated with the demolition.

“The university hired a demo consultant to come and look at their buildings to come up with a plan for the best possible scenario to get those two buildings down safely with little to no risk to the general public,” Harrison Williams, project manager at Ark Wrecking, says. “They talked about breaking it down mechanically, both balling it down or utilizing UHD (ultra-high demolition) tools, but the problem with both of those options is the time of exposure during the demolition would require multiple weeks. They were more interested in the building being on the ground immediately.”

Prepping the buildings

After Ark Wrecking rid the building of combustibles, the next order of business was to select an abatement contractor to begin the asbestos removal. The job was awarded to Bockmann Inc. of Lincoln, Nebraska, which got to work right away.

“Getting the asbestos abatement under contract and started in early May was really the key to getting the project going and maintaining the schedule the university was interested in,” Williams says.

Once the asbestos abatement was completed, it was time for Ark Wrecking to prepare the buildings for implosion. The company performed a soft strip of carpets, wood and other deleterious materials so that the postimplosion debris could be recycled. It then gutted seven floors in each tower by removing all the nonloadbearing block walls and masonry, as well as the interior partitions, to strip the buildings down to the mainframe.

To complete the interior demolition work, Ark Wrecking purchased a Brokk 110 remote-controlled demolition robot with a hammer attachment. The Brokk 110 was chosen, according to Williams, for its ease of climbing stairs and fitting in tight spaces, which was needed to maneuver through the facilities’ door frames.

The shear walls around elevator shafts and stairwells were modified per CDI’s design to create flat wall elements, which CDI’s drillers could effectively prepare for the placement of charges.

Ark Wrecking also placed at-source protection made of chain link fence and geotextile fabric around columns and walls to be shot by CDI. Additionally, it placed chain link fence and geotextile fabric curtains around the shot floors to help contain any particles that escaped the at-source protection.

During this time, the common area adjoining the two high-rise structures was conventionally predemolished.

The implosion

CDI went to work reviewing the project details at length when preparing the company’s subcontract proposal for implosion preparations and execution.

“We reviewed the structural plans provided, inspected the structures in the field to confirm information provided by those structural drawings and reviewed the nature, location and condition of adjacent improvements to remain undamaged,” Mark Loizeaux, president of CDI, says.

The decision to implode these buildings made a lot of sense, Loizeaux says, and helped minimize risk for all parties.

“From CDI’s perspective, implosion was selected because of the size and suspension methods of the precast panels around the perimeter of the building, the proximity of adjacent improvements and public/student rights-of-way to remain,” Loizeaux says. “Dealing with those large precast panels would have been difficult, at best, over several months of dismantling if conventional demolition had been used. The duration of exposure to the public and student body for that extended period of time, while the precast panels were picked off, would have created long-term risk that the university, and the main contractors, would have wanted to avoid.’

Loizeaux says the precast panels came down in seconds during implosion. “The dramatic reduction in duration and nature of risk associated with conventional dismantling would have been enough to steer the university toward an implosion approach designed and executed by an experienced and qualified contractor.”

Cleanup and recycling

The materials to be recycled were somewhat limited because the building was composed mostly of block walls and concrete deck ceilings, and the floor tiles that were removed during abatement were unrecyclable.

“During our gut-out process, we recycled approximately 30,000 pounds of precious metal, basically copper and aluminum,” Williams says. “We also extracted roughly 22,000 tons of concrete.”

He adds, “The university had worked out a deal with the city, which owns the Bluff Road landfill in Lincoln, for the landfill to sort through all that concrete and recycle it to use for roadbed for road construction within the landfill site, which is around a 120-acre site. There was very little ferrous material.”

Ark Wrecking used 80,000-pound track excavators to help with the material cleanup and is continuing to work on-site with crews of five to eight employees to complete the project by its April deadline.

Ark Wrecking tabbed Gana Trucking & Excavating in Martell, Nebraska, as the earthwork contractor to help with the material cleanup.

A smashing success

Every demolition job has certain risk factors associated with it. The implosion of Cather and Pound Halls was no different.

In addition to the regular prep work, Ark Wrecking and CDI had to consider the buildings’ proximity to nearby structures when planning their project.

According to Williams, the dorms were flanked on two sides by other buildings, and there was a new building in front of the property with a three-story curtain wall that also warranted some consideration.

“The unique challenge of this job was just the close proximity to other buildings,” he says. “So, the biggest challenge was the amount of protection and precaution we had to take to protect the surrounding buildings. My biggest takeaway is you can never figure enough protection.”

In the end, the demolition and implosion went off without a hitch, which will allow the site to be converted into green space by the university in May or June.

According to Loizeaux, proper planning and collaboration helped to negate any potential issues that could otherwise have occurred during the demolition and allowed the project to go on as scheduled.

“From CDI’s perspective, the implosion of Cather and Pound Halls was a textbook operation with the structures behaving precisely as planned,” Loizeaux says. “The university representatives were professional and easy to deal with, and Ark Wrecking brought all of the experience and tools to the table to prepare the structures exactly to CDI’s specifications. The successful implosion of these two structures was the result of a team effort by all.”

The author is editor of Construction & Demolition Recycling and can be reached at aredling@gie.net.