“All you can do is laugh,” said Jim Wutzke, demolition manager with Frattalone Companies Inc., of St. Paul, MN, when 100 lbs. (45.3 kg) of explosives failed to topple the 202-ft. (61.6 m) Zip Feed Mill in Sioux Falls, SD.
When the button was pushed to create the explosion, the structure was expected to lean 15 to 20 ft. (4.6 to 6.1 m) to the west and then tip and fall to the east. The process started out as planned, but it failed to tip to the east; it hit the leaning stage and there it sat. “It is being called the Leaning Tower of Zip,” Wutzke said. “The crowd was chanting, ’Tip the Zip.’”
To decide who got to push the button, raffle tickets, about 25,000 of them, were sold to raise money for Multiple Sclerosis. T-shirts were also sold with a simple statement, “Boom,” printed on them to raise money for MS. Property owner, Jeff Scherschlight’s daughter was diagnosed with MS during the summer.
The building is being demolished to make room for future development on the east bank of the river in downtown Sioux Falls.
To prepare for the explosion, some attached buildings were removed so there were no restraints when the building fell. Lower level rooms were removed and the exterior walls on the east half were removed between the columns so the structure looked like it was standing on stilts, the interior was washed to remove any environmental hazards and the pigeons were cleared out, Wutzke explained. Then 96 holes were drilled in the columns and filled with explosives. On the east side, the wall was cut away from the foundation to aid in the tipping process, he adds.
“The columns came out as they were supposed to as did the back of the building that was to hold the structure until it tipped and collapsed,” Wutzke said.
Project Manager of Henry Carson Company, prime contractor of the project, Eric Schuler, added, “The plan was to lower the eastern section, creating a wedge to allow the building to tip somewhat, like is done when removing a tree. The west side was to remain ridged but that failed.
“We were definitely surprised when it didn’t tip to the other side as we had planned. We entered a review stage to regroup,” and came up with a new plan – to remove the structure the old fashioned way - with a crane.
“We had to bring a crane out anyway because we never expected the bins inside to breakup,” Wutzke said. “When the building didn’t fall we just had to bring out a bigger crane.”
He explained that the bins inside the mill were encased in 6 ft. by 6 ft. by 8 ft. (1.8 by 1.8 by 2.4 m) concrete boxes, creating a honeycomb situation. The bins sat between the elevations of 30 ft. (9.1 m) and 170 feet (51.8 m) within the structure.
Explosives were chosen for the demolition because the structure was about 40 ft. (12.1 m) too tall for even the company’s largest crane to handle. After the blast, the height was lowered to about 160 ft. (48.8 m). If all had gone as planned with the explosion, the building would have been lowered to about 80 ft. (24.4 m), requiring a smaller crane.
The bigger crane, a 180-ft. (54.9 m), 100-ton (90.7 t) American 999 and 200 ft. (61 m) of boom, was hauled from St. Paul to Sioux Falls taking about eight semi loads. The crane requires a day and a half to set up and another day and a half to tear down. “This is the largest crane we have,” Wutzke said, adding they have two of them in the company and if they had been tied up in another job, “We wouldn’t have cared. It would have been here.”
Around mid-December, about 30 ft. (9.1 m) of the structure remained. Demolition of this cast-in-place, all concrete structure is a little slower than demolition of a masonry building would be, Schuler says, but it is proceeding as planned.
The Zip Feed Mill, named so because the feed was said to give the animals zip, Wutzke explains, was built in 1955.
Wutzke commented, “This (failed explosive demolition) is more common than people think. What is important is no one got hurt and everyone got a good laugh when the country needed a good laugh, but we’ll win, we always do. The 999 American doesn’t take any guff from buildings like that.”
By Christmas, only 15 ft. (4.6 m) of structure remained above grade. At that point an excavator will be used to complete the demolition. When removal of the basement takes place, more sorting will be required with visual inspection to make sure there are no contaminants in the concrete, Wutzke explained. Workers were prohibited from going into the basement before the blast because it contained 11 ft. (3.4 m) of water that was deemed dangerous.
Once demolition is complete, the rebar has to be separated from the concrete, a process that is expected to be complete by mid-January, Schuler added. The concrete will be pulverized and then crushed with a crusher early in April so water can be sprayed for dust control; “You can’t do that with the freezing conditions in the winter.”
The crushed concrete will remain on site and be used as the base for a parking lot, Wutzke said. “We would have spent the same amount of time processing the material if the explosive option had succeeded. It would have been nice to have it tip over to the 80-ft. height vs. the 160 ft.”
The $400,000 demolition cost remained the same, but the company suffered the cost of drilling for the explosives.
Scherschlight, president of Howalt-McDowell Insurance Inc., and partner Raven Industries Inc., in the redevelopment of the east side, is planning a 100,000- to 115,000- sq.-ft. (9,290- to 10,684-sq m) office tower with the hope it will spur future development.
He added he is working with the city of Sioux Falls to sell them 162,000 square feet (15,050 sq m) on which to build a $100 million event center. The city has five years to act on the option; if they don’t, future construction plans could change.
“If the event center is built, we will build about 40,000 square feet of retail space,” Scherschlight said. Apartment buildings, restaurants and bars could also be added in the future.
Planning for the office tower will begin the first part of January, Scherschlight said. “We hope to break ground by April. Construction will take one and one half years. We want to occupy the building by Jan. 2008.” CEG