The 15-story apartment building and eight-story office building that were Keystone Towers crumbled Sunday morning, except for the solidly built elevator shaft.

Because of the shaft's reinforced construction, it was deemed unsafe by workers to include in the demolition preparation, said Frank Burdick, project estimator for Denney Excavating of Indianapolis, which is preparing to do the cleanup work and shaft demolition.

Some explosives were placed beside the elevator shaft, he said, but there were concerns about cutting into the shaft for more effective placement.

"We would have liked for the elevator shaft to fall, obviously," he said shortly after the apartment building and office building along Binford Boulevard, just east of Keystone Avenue, collapsed from 750 pounds of strategically placed explosives.

Congrats to Denney and Advanced Explosives!