The smaller the space, the bigger the plan

Partnering with Phoenix, Maryland-based Controlled Demolition Inc. (CDI), The Berg Corp. faced a tall task in preparing to implode the Holiday Inn Rosslyn in Arlington, Virginia.

Austin Berg, director of business development for Berg Corp., says the company would have preferred to take down the 20-story hotel mechanically, but that was not an option.

“The whole reason we imploded was because it was a post-tensioned structure,” he says. “We weren't comfortable with taking the top three or four floors out mechanically with Brokks because we didn't know how the building was going to sway with the post-tensioning.”

Berg says the 2020 demolition was challenging because there were “brand-new towers right next to us and utilities that we had to take care of.”

In addition to preparing the 210,000-square-foot tower, there also was a garage that needed to be dismantled.

“There was also a three-story parking garage connected to the building that we took down mechanically with machines,” he adds. “It just helped us have more area and a better space for the material to fall into.”

‘Risky’ garage demolition

The garage also was a post-tension structure, Berg says.

“That was a pretty risky demo, taking that down,” he says. “We were probably a month taking the garage down before the implosion.”

Post-tension construction uses wires or cables as additional reinforcement for concrete, and Berg says that can make manual demolition dangerous for machines and workers on the building being taken down.

“Back in the day, they used post-tension construction where they had wires on each floor that were wound up, and, really, the tension on it was tight,” he explains. “If you demo one of those sections, if you break the tension on the wire, everything can cave in on itself.”

Photo courtesy of The Berg Corp.

Taking care of the neighbors

The Rosslyn Apartment Tower, a new residential building, is located directly to the south of the hotel and required a very tightly controlled implosion.

Because of the proximity of the apartment building, Berg said the company went out of its way to make sure the residents understood the process.

“The closest building to that implosion was a high-end condo association,” he says. “By the end of the project, I knew every single person in that building from talks and meetings and just making sure that they're comfortable with what we're doing.”

Berg says he also had to coordinate with the Federal Aviation Administration (FAA).

“We were kind of close to the flight path going to ... Reagan National Airport,” he says. “We had to give them notice 30-minutes before, and there was lots of planning, lots of meetings, as well.”

The firm also had to coordinate with the Washington Metropolitan Area Transit Authority (WMATA), which has a subway station several hundred feet from the implosion site.

“We had to had to shut them down for 30 minutes while we did the implosion,” he says.

He says Berg also had to shut down Interstate 66 for a period during the implosion, as well as some of the streets immediately surrounding the hotel.

CDI notes in a project profile that gas, water, electric and fiber optic lines under Nash Street and Fort Myer Drive are as close to 4 feet from the base of the tower.

Although the hotel fell in on itself during the CDI-designed implosion, Berg says the closures were needed in case anything went wrong. In its profile, CDI says it had to install 40 cables in the east and west ends of the tower so they could be pulled away from the adjacent streets.

Berg also took measures to protect utilities, streets and the residential tower.

“We had steel plates over the utility lines; it was months and months of preparation for this implosion,” he says.

Keeping it contained

 Dust protection alone—an unavoidable byproduct of an implosion—took some planning. In addition to “shooting for a rainy day,” Berg says the firm took a variety of measures to protect the condominium building nearby.

“The measures were actually pretty extensive for that neighboring property,” he says. “We actually had to cover a lot of their HVAC units; we had to do work on the balconies that faced the actual implosion.”

To protect other nearby buildings from dust and any errant chunks of debris, Berg Corp. used boom lifts to hang tarps side-to-side 40 to 50 feet in the air.

Sea containers also lined the streets, and there were six or seven dust machines running during the implosion. The containers acted as barricades so debris wouldn’t fall onto the surrounding streets, he explains.

CDI President Mark Loizeaux says that implosion design is based on meticulous study and planning.

“Demolition modeling is generated from whatever structural plans are available on a structure or observations that can be made by the firm performing the modeling,” he explains. “They are then blended with timing and implosion preparation details generated by the explosives demolition company to create a ‘picture’ of what the building will look like when it is being felled.”

The placement of charges is planned to minimize vibration to surrounding buildings and infrastructure and control the direction the building falls, he adds.

“A well-designed implosion releases … potential energy in a fashion to control the felling direction and velocity for the structure, converting that potential energy into kinetic energy which can generate superb fragmentation of the structure in ‘midair’ to reduce vibration from the arrival of that debris at grade and facilitate the mechanical removal of same by the debris removal contractor,” he says.

Stripping down the building to prepare it for implosion took several months, Berg says.

“Ultimately, we got all the trash out; we gutted the whole building, 21 stories, back to the concrete shell,” he says. “We took out the windows on every other floor; we wrapped all the columns. … So, it was extensive work to get it ready for implosion so what we were left with was a clean pile.”

Still, as much time as the physical work took, communication with all the different entities was among the most time-consuming parts of the urban job.

“We had a huge action item spreadsheet that I'm looking at right now. We started our first communication in April 2020 and blew it in December of 2020,” he says.

The hotel was owned and built by Dittmar Co., Dunn Loring, Virginia. In a letter from The Dittmar Co.’s Kyle Woodbury to Loizeaux, Woodbury commended the implosion company on its work.

“Initially, the notion of an implosion was difficult for us to seriously entertain,” Woodbury wrote in the December 2020 letter. “CDI explained to us, ‘No, we are not going to ‘blow up’ the building; it’s an implosion; it collapses inward safely and in a controlled manner.”

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