KHOU Houston Doomed Booms. The 420-ft-long lattice boom (red, left) took out a smaller one as it fell down.

Investigators haven’t said what caused a July 19 crane collapse that killed four workers and injured seven others in Houston. Initial reports point to the machine’s counterweights as a possible source of one of the deadliest U.S. crane accidents in the past decade.

The accident occurred at a Houston refinery owned by Netherlands-based LyondellBasell. A custom-built, VersaCrane TC-36000, equipped with a back mast and 420 ft of main lattice boom, snapped at its base and crashed into a smaller crane before hitting the ground. Killed were operators Marion “Scooter” Hubert Odom III, 41, and John D. Henry, 33; as well as ironworkers Daniel “DJ” Lee Johnson, 30 and Rocky Dale Strength, 30. All worked for Baton Rouge, La.-based Deep South Crane & Rigging, the crane supplier. Two workers remain hospitalized.

Soon after, two lawsuits were filed in state court. The probe is in “very early stages,” says Byron Buchanan, a lawyer with Brent Koon & Associates, Houston. Based on preliminary inquiries, he says, investigators are looking at the 2,500-ton-capacity crane’s counterweights for clues. Law firm Williams Kherkher, Houston, is representing Grant Pasek, who was injured after jumping from an elevated bucket when he saw the crane start to fall. Buchanan’s firm is representing Paul M. Musick, who was injured while trying to escape the falling crane. Neither Pasek or Musick worked for the crane contractor.

Described as one of the largest mobile cranes in the U.S., the Versa-Crane was slated to perform maintenance work on the refinery’s coking unit. A test lift was performed on July 18. The crane was not scheduled to operate the day of the collapse. Refinery officials say the engine was running after the boom fell, however. “At the time of the accident, the crane was not performing any lifts associated with the turnaround,” confirms Lisa Walsh, refinery spokeswoman. “Part of the investigation will determine what activities the crane was involved in at the time of the incident.”

The crane was dispatched to Houston from a CITGO refinery in Corpus Christi, Texas, about a month ago. It boasts a low ground pressure, says Margaret Landry, Deep South spokeswoman.

Officials from the U.S. Occupational Health and Safety Administration are investigating the accident, which follows a spate of recent high-profile crane fatalities.

Texas, which does not require crane personnel to be certified, led the U.S. in crane-related fatalities in 2005 and 2006, according to the U.S. Department of Labor, with a combined 26 deaths out of the 157 reported nationally.

Federal data after 2006 are not yet available, but according to craneaccidents.com, an independent safety clearinghouse, six workers died in crane accidents in Texas in 2007. Nine crane-related deaths had been reported to the site for Texas in 2008.

Texas lawmakers say they are evaluating further industry regulation.

Forensic crane experts, meanwhile, agree that custom-built cranes, while unique, are not different than mass-produced cranes in terms of configuration requirements. “The only reason custom made becomes somewhat of a concern is that you don't have a huge population of similar devices out there trying to hurt themselves,” says Brad Closson of CRAFT Forensic Services, Bonita, Calif.

“It should not have significant impact,” says Steven Smith, group manager for CTLThompson, Washington, D.C. “The design and operation standards should be the same as any other crawler crane.”

He adds that custom cranes need to be held to the same standards of any equivalent crane that is mass produced. “We have to look at the operational history. If we start to see that there are a greater number of failures with custom cranes, we have to step back and say it is a concern.”

Smith says one challenge is the lack of operational history and knowledge base that comes with a more organic development of cranes over time. “Often cranes evolve by being developed from smaller ones. That counts for quite a bit.