Peek inside EnviroVantage’s demolition playbook

brokk demolition

The Wildcats Stadium at the University of New Hampshire makes for an exciting scene, with the exception of one element: the announcer’s box.

Standing above the stadium like a stout linebacker, the dark blue structure was considered an eyesore by the university. Dubbed the “Blueberry” due to its colour, the building had to go.

Construction of a new athletic facility across the field from the box, and field house to which it was attached, prompted plans to demolish the Blueberry. University officials wanted to remove the unsightly structure and install handicap seating in its place. They hired general contractor Charter Brothers Construction for the quick-turnaround job, seeking to have it finished in time for the fall football season.

Charter Brothers chose to subcontract the demolition portion of the project to EnviroVantage, a company with 30 years of experience in that industry. Scott Knightly, EnviroVantage owner and president, said one reason Charter Brothers selected them for the job was their Brokk 100 remote-controlled demolition machine.

“We do a lot of work on campus already, so we’re familiar with the area,” Knightly said. “In this case we also had a Brokk machine, which really was the best and most cost-effective way to do this project.”

Knightly knew demolishing the box would require precision. The Blueberry sat above locker rooms as well as aluminum stadium chairs that could be easily damaged by falling debris. The rest of the field house contained a swimming pool, basketball courts and other athletic features. EnviroVantage needed to complete the job without damaging the surrounding area or disturbing or endangering summer students.

The announcer’s box wasn’t going down without a fight. The Blueberry was heavily-reinforced, including 12 in. thick concrete walls, floors and ceilings, all strengthened with 1 in. diameter rebar. In addition, space inside was limited. The box’s three levels were each 500-sq. ft. and only about 6 ft. tall.

“I’ve never seen so much rebar in my life,” Knightly said. “I knew we would have to work hard and use our most productive techniques and tools to get this project done on time.”

Game plan calls for a robot

Knightly considered several demolition methods for the project, but the location of the box, limited space and its composition made most traditional demolition methods nearly impossible.

There wasn’t enough room for a crane or high-reach excavator to manoeuver without damaging the track or field. EnviroVantage also couldn’t use large, handheld pneumatic tools because of the risk of vibrations causing micro-fracturing in the main structure. Crews tried using chemical expansive demolition agents, but the method was ineffective.

Knightly knew the most suitable option was to use the company’s Brokk 100 remote-controlled demolition machine to remove the structure. He knew pairing the machine with a concrete crushing attachment would minimize most of the noise and vibrations. The machine also delivers more power than a worker with a handheld tool.

When demolition began, the project’s biggest snag happened almost immediately, putting the deadline in jeopardy. Knightly originally planned to build scaffolding and drive the Brokk machine to the top of the structure and demolish from the top down. However, he learned just a week or two into the project that the concrete contractor required 30 days of curing time to complete the next step of the project following demolition. The change cut a month out of

EnviroVantage’s initial three-month schedule and made the original plan impossible. The scaffolding would take two weeks to put up and another two weeks to take down.

“We tried to arrange for the scaffolding to be put up faster, but it just wasn’t going to happen,” Knightly said. “We had to figure out something else. Fortunately for us, we had the versatility of the Brokk machine.”

EnviroVantage demolitionBreaking in to break out

The plan changed from demolishing the box from the outside. Instead, they decided to break in and destroying the structure from the inside out. Knightly would use the Brokk 100’s precision, power and compact size to chew into the structure.

The demolition required special safety measures, as there was nothing above the structure to tie on to. Workers core drilled into the concrete and installed channel angles to be used as tie-offs for crew members.

To prevent debris damage, crews placed double layers of plywood and tires below the structure to cushion the blow from falling concrete. In addition, workers bolted chain link fencing in front of the box to catch debris.

EnviroVantage also placed a 35-ft. conveyor near the project to deliver material over the field house’s railing, down a chute and into a dumpster 25 ft. below.

Workers used small, handheld Hilti breakers to remove the roof after completing the abatement. The rooftop work was a slow-going, hot process. Temperatures reached as high as 120 F.

Demolition deadline

With two and a half weeks until deadline, EnviroVantage moved in with the Brokk. This required widening the announcer box’s doorway and climbing steep staircases to get to the top level, just below the roof. Crews built ramps to allow the machine to drive up the almost vertical staircases. They manoeuvered the Brokk 100’s three-part arm to help pull the 2,200-lbs. unit up at a 70-degree angle.

After it reached the third level of the box, EnviroVantage put the machine to work. The B100’s 13-ft. reach, coupled with the Darda CC340 concrete crusher’s 37 tons of power, allowed the operator to demolish the majority of the walls around the machine. The contractor only used the machine’s breaker attachment occasionally to get at hard-to-reach corners.

“We were working seven days a week at that point, so productivity was key,” Knightly said. “It was unbelievable how easily the Brokk demolished the concrete, especially since the other methods we tried barely scratched it.”

After demolition of the top floor was completed, crews moved the B100 to demolished the ceiling and walls. They then moved the machine outside the structure and continued demolition until the box was level with the top of the stands. Workers used concrete saws to assist the machine along the way.

The remote-control operation of the unit kept workers away from safety hazards inherent in demolishing a ceiling. This reduced the risk of hand and arm injuries related to constant exposure to vibrations.

In the end, EnviroVantage finished its portion of the project in 72 days of work. In all, they removed 105.8 cubic yards of concrete and rebar. Then, the next contractor moved in to prepare the demolished area to be turned into handicap-accessible seating.