As July approaches, the scheduled implosion date of Knapp and Storms Halls has been narrowed.

The exact date of the demolition within the current range — July 19 to 21 — depends on how quickly the demolition subcontractor is able to prepare the site and will not be known until a few days before implosion.

“At this time of year, there really is very little in the way of weather that would prevent us from going on the day specified,” said Kerry Dixon-Fox, project manager for facilities planning and management, adding the demolition could be delayed for a few hours to wait for bad weather to blow over.

She said the demolition subcontractor, Controlled Demolition Inc.of Phoenix, Md., must drill more than 1,000 holes in steel-reinforced columns in both buildings to place explosives in.

Dixon-Fox and Gene Deisinger, ISU Police Captain, said Facilities Planning and Management is working with DPS to coordinate crowd control for the event.

They said there is no estimate of the number of spectators at the event.

“We have been told by Controlled Demolition Inc. that they typically see anywhere from five to eight thousand people,” Dixon-Fox said.

Dean McCormick, assistant director of construction services for facilities planning and management, said a 750-foot buffer zone between spectators and the buildings is now planned, although the zone size could be reduced.

Dixon-Fox said the 750-foot estimate would be more appropriate for a crowded downtown area.

“When you’ve got as much open area around the buildings as we have, the dispersal (of dust) will be much quicker,” she said.

Dixon-Fox said dust from the implosions should settle in approximately 15 to 20 minutes.

She said explosive testing is scheduled for this week, although nothing will be visible from outside the building.

The tests involve inserting explosives in non-critical columns and wrapping them in a chainlink fence and Tyvek, a construction material.

“It’s kind of like shooting off fireworks in a toilet,” Dixon-Fox said.

“You get a loud noise and everything is contained.”

McCormick said no decision on the futures of the other two towers, Wallace and Wilson Halls, has been reached yet. The hub between the towers is planned to remain open as an ISU Dining facility. The ground left by Knapp and Storms is planned to be used as green space, he said.

Dixon-Fox said the contractor, Peterson Contractors Inc. of Reinbeck, Iowa, should be finished clearing the site by early September.