The owner’s investigation continues into why a 275-ft-tall concrete smokestack fell in an unexpected direction when it was imploded on Nov. 11 during demolition of FirstEnergy’s largely unused Mad River powerplant in Springfield, Ohio.
Because no one was injured in the accident and proper procedures seem to have been followed, the Occupational Safety and Health Administration will not pursue an inquiry, says an agency spokesman.
The plant, about 28 miles northeast of Dayton, is an old coal-fired Ohio Edison generating station now owned by FirstEnergy. The utility is retiring a number of generating plants, including Mad River, which was originally built in the 1920s; it has been mostly unused since the 1980s.
Mark Durbin, spokesman for FirstEnergy, says the utility hired Bet-Tech Construction Co., Monaca, Pa., as the project general contractor.
In turn, Bet-Tech subcontracted Independence Excavating Inc., Independence, Ohio, for demolition work at the site.
Independence Excavating then subcontracted implosion of the tower to Advanced Explosives Demolition Inc. (AED), Coeur D’Alene, Idaho.
“All of the companies involved in this project are extremely pleased that no one was hurt. We consider safety as job No. 1,” says Ray Wiecek, Independent Excavating risk-management director.
Although the investigation is still in its early phases, AED believes there may have been an unseen crack that caused an unexpected weak point in the reinforced concrete stack, the diameter of which is 21 ft, 10 in. at its base.
Lisa Kelly, president and owner of AED, told the Springfield, Ohio, News-Sun newspaper that an undetected crack in the tower caused it to topple in a different direction than expected.
The tower was supposed to fall eastward into a cleared area; instead, it fell to the southeast, taking out two 12,500-volt power lines and damaging two oil-fired turbines that are still in use on a backup basis.
FirstEnergy’s Durbin says that about 4,000 customers were without power for a couple of hours after the accident.
Durbin says the utility will decide whether to repair the two oil-fired turbines, which generate a total of 60 MW, when it determines how badly they are damaged.
Eric Kelly, AED’s chief blaster and a co-owner, says the implosion company is working with the contractors to find out why the smokestack fell in an unexpected direction.
“We [AED] think that there may be some information about structural deficiencies in the stack that would have been useful to know in planning the implosion but that we weren’t given,” he says.
“During preparation of the stack, we weren’t given a condition report about the structure. But it’s not unusual for there to be no condition report for something this old,” says Kelly.
He says that, after the implosion, a consultant on the project asked whether he had seen the condition-of-structure report.
“If I had known there were deficiencies, I may have planned to drop the stack in a different direction,” Kelly says.
Kelly says he planned to drop the smokestack right where the overall demolition contractor asked.
“I did everything by the standard procedures. It was textbook. You establish a fulcrum point. Put the stack on ‘legs’ [by removing parts of its base], then blow it in sequence to lay it down in the direction you want,” he says.
Kelly says it took just 17 lb of binary explosives detonated in blasts milliseconds apart to bring down the tower.He says that, in 31 years of imploding thousands of structures, this job is only his fourth that didn’t go as planned—and only the second in more than 25 years.
“I just successfully ‘shot’ an 85-ft-tall building in Athens, Greece, with only 15 ft of clearance on two sides and 30 ft of clearance on the other two,” he says.