Elevator, Going Down

A sizable grain elevator and its accompanying silos presented a formidable challenge for the demolition division of Frattalone Cos., St. Paul, Minn.

Adding to the challenge was the need to stay within a tight time frame and to keep vibrations to a minimum for a nearby university research center.

Jim Wutzke and his team from Frattalone Cos., however, met all their goals on the project while recycling virtually all of the more than 50,000 tons of debris at the job site.

Frattalone Cos. submitted the winning bid to take down a Minneapolis grain elevator complex that had been owned by ConAgra.

Throughout recent decades the University of Minnesota had been growing its footprint in the same part of the city. When university officials were seeking land on which to build a new football stadium, the parcel with the ConAgra elevator complex was purchased.

Before the University of Minnesota Golden Gophers football field of dreams

Builders wanted to start as early in the construction season as possible, since it’s a season that can be comparatively brief in Minnesota compared to most other parts of the country.

The window left for Frattalone Cos. to work in was a stretch of late fall and winter weather that started in November of 2006 and concluded on March 31, 2007. "It couldn’t be a real long project," notes Wutzke.

Because of the quick timeline, explosives were considered. "Explosives could have been an option, but the University’s magnetic resonance research center was about 200 feet away," notes Wutzke. "They could not even give us a threshold value of vibration tolerance—they didn’t want to the take the chance."

With implosion off the table, formulating the best techniques to reach the necessary 195 feet to the structure’s highest point became the next order of business.

The ConAgra-University of Minnesota project was not the first grain elevator tackled by Frattalone Cos., and Wutzke says the company used established procedures starting at the estimating stage.

"Even before we bid the job, I asked our surveyor to go out and determine the heights of the structures so we could calculate the quantity of debris," says Wutzke.

Calculating the amount of debris was important for two reasons: to know how much saleable material would be created, and to determine if a sufficiently-sized ramp could be created to allow the company’s crane to reach the highest points of the structure.

The company determined that the head house—the rectangular building that holds conveyors and elevators that is the highest part of the complex—was 195 feet in height.

The company’s American cable crane had previously helped demolish head houses up to 210 feet in height—but a ramp of rubble was needed.

On the ConAgra job, some of the initial concrete debris was gathered and compacted into a 40-foot hill or ramp up which the American cable crane crawled so its operator could then continue to wield the wrecking ball into the head house.

"After bringing it down with the crane, we processed that first debris by having a Caterpillar 235 excavator with a LaBounty pulverizer munch it down to basketball-sized pieces," says Wutzke. A pile that consisted of two feet or smaller sized rubble ("a lot of it smaller," he notes) was used to build a pile that is stable enough for the cranes to keep using throughout the job.

After the highest parts of the structure had been reached, a crew with designated equipment and assigned tasks kept the project going throughout the winter.

Tearing down the head house and silos from the top down made up just one portion of the overall project, Wutzke points out.

What is taken down also has to be disposed of or recycled, and in this case "recycled" was the operative word.

As the job advanced, "The crane would bring down the head house and silos, and an excavator with a grapple would pull debris away from the working area," says Wutzke.

That debris was put in front of another excavator with a pulverizer attachment that would "process it, extract the rebar and downsize the concrete so it would fit into our crusher," he adds.

Some 56,000 tons of debris was generated, including 50,000 tons of concrete "waiting for the crusher spread to move in," according to Wutzke.

A Cedarapids jaw and cone plant crushed the material to meet Minnesota DOT specs for road base material. "Most of that material was used right in the immediate area, for the base of parking lots and roadways to the new stadium," says Wutzke.

The rest was spoken for quickly. "That material in that part of town was a pretty hot commodity; that pile was sold before the job was even complete," Wutzke notes.

The nature of the debris was one of several factors contributing to the favorable demand scenario. The head house was made from reinforced concrete, and the silos were made of slip-form concrete, which is also reinforced but with spiraled steel hoops rather than rods.

"It was good feedstock for our crusher," says Wutzke, noting that once the steel was removed from either type of debris, "it was 99-9/10ths pure concrete, with no brick or block or tile, and everybody wanted it."

The crushing plant operator "was making up to 3,200 tons on his best days," recalls Wutzke, who said the plant was producing at rates of from 250 to 350 tons per hour.

Frattalone Cos. also had the good fortune of selling the scrap steel reinforcing bar to metals recyclers while the pricing for ferrous scrap was at a lofty level.

The successful disposition of the material capped the end of a project that went well from start to finish and that also gave Wutzke pride in how the company performed.

"We’ve now taken down a few silos and elevators with this same process, and we’re getting pretty quick at it," he remarks. Sharing the credit, Wutzke adds, "Our superintendent Arlen (Red) Richter has really become awesome at this."

The job went so smoothly that Wutzke comments, "The unexpected thing is that we didn’t hit any surprises. The University of Minnesota did an exemplary job assigning a team that helped us out and that connected the dots from start to finish."

Construction of the stadium is now underway, and Wutzke will be reminded of the demo job in upcoming football seasons. Frattalone Cos. owns Golden Gophers season tickets, and Wutzke is usually able to attend at least one game each year.

He is pleased that he had a role in creating the new structure. "I take pride in knowing the Gophers will play there," Wutzke comments. "I am an alumnus, so there is a lot of personal satisfaction with this job and with how well it all went."