Day: June 24, 2022

Grain Explosion Evaluation


A large grain dust explosion occurred at a grain company facility. The explosion severely damaged three connected silos and injured six workers, as employees were loading rail cars when the explosion happened, and sections of the bins toppled onto the rai.

On August 13, 2014, a large grain dust explosion occurred at the Coshocton Grain Company facility in Coshocton, Ohio. The explosion severely damaged three connected silos and injured six workers. Employees were loading rail cars when the explosion happened around 4 pm, and sections of the bins toppled onto the rail cars.(1)

The 60-year-old Coshocton Grain facility was a 2.5-million-bushel capacity grain receiving, drying, and storage facility that included three slip-formed concrete storage houses standing more than 100 feet above grade at the bin deck. A single gallery spanned across all three houses; two of the houses had head houses. A tunnel network connected all three grain houses in the basement, and one of the houses to a truck dump building and to several silos across railroad tracks to the south. South of the railroad tracks were five additional concrete silos, four steel storage bins, and several small buildings.

Seven bucket elevators, 12 drag conveyors, 11 belt conveyors, two screw augers, and one tripper directed the flow of grain throughout the facility. In general, the equipment in the basement and ground-level directed flow of grain away from the dumps and bins, and to the boots of the elevators. Elevated equipment directed flow away from the elevator legs to the various silos, bins, dryers, and load out areas of the facility. There were also three dust collectors, a dryer, a truck scale, and a continuous flow scale.

Haag responded to determine the origin and cause of the explosion, which included coordinating with OSHA representatives and salvage efforts.

The explosion caused a large area of the middle house to blowout and the head house to fall to the ground and damage several railcars and railroad tracks. Haag’s original scope expanded to include documentation of the explosion site using 360° photography and scanning (3D laser scanning), evaluation of structural and mechanical damage caused by the explosion, and a cost estimate of the explosion-related damage. 


Involved Experts: 

Ground Surface Dropout at Residence

Basic Fact Pattern

During a site stabilization, a surface dropout occurred below the residential structure causing additional damage to the foundation and walls.

Investigative Actions Taken

Haag performed a geotechnical subsurface evaluation of a residence related to possible sinkhole activity. Our study of the property involved exploratory drilling and sampling, shallow excavation, a geophysical survey and laboratory testing. Our findings revealed highly weathered limestone at depth and formed cavities and voids from soil raveling associated with sinkhole activity. 

Determinations Made

Haag recommended a program of deep compaction grouting and shallow chemical grouting to stabilize the building pad. During stabilization, several surface dropouts occurred. Haag quickly responded to develop plans for stabilizing the ground and residential structure. Haag monitored the filling of voids below the foundation and slab with a cement slurry and rapidly implemented a grouting program to treat raveled soils and limit property damage.

Involved Expert: 

Hoover Dam By-Pass Bridge Collapse

Hoover Dam

The Hoover Dam’s By-Pass lifting system, a luffing cableway supported by four towers, collapsed during high winds.

The Hoover Dam By-Pass Bridge was part of the new alignment of U.S. Highway 93 across the Black Canyon between Arizona and Nevada and was located approximately 1,500 feet downstream of Hoover Dam. Total length from abutment to abutment was approximately 1,090 feet.  The structure was the first concrete-steel composite arch bridge built in the United States and includes the longest cast-concrete arch in the Western Hemisphere. The Obayashi Corporation and P.S.M. Construction USA, Inc. Joint Venture (Obayashi/PSM JV) was awarded the bridge construction contract by The Federal Highway Administration (FHWA). HDR Engineering, Inc., and T.Y. Lin International were the bridge design team.

For construction of the bridge, the By-Pass lifting system was a luffing cableway as defined by the American Society of Mechanical Engineers (ASME) B30.19 – Cableways. Four lattice towers, each approximately 330 feet tall, were erected on either side of the Colorado River immediately south of the Hoover Dam. Distance between the opposing towers (span) was approximately 2,500 feet. The two cableways extended parallel and along the centerlines of the double highway lanes of the new bypass bridge. Each tower could lean (luff) in the north/south direction to provide lifting capabilities for the load block to reach the entire width of each of the double highway lanes. Lower and upper load blocks were supported by a carriage that was positioned along the spanned length by inhaul and outhaul ropes on the track cables (gut lines).

During high winds on September 15, 2006, the Nevada South tower buckled and collapsed.  During the collapse, the falling sections severed multiple support cables of the Nevada North tower causing it to fall to the north.  The resulting collapse of both Nevada towers imparted dynamic loading to the two Arizona towers, causing both to fall westward toward the Black Canyon of the Colorado River.

Haag Engineering Co. was retained to determine factors causative of the collapse and evaluate duties and responsibilities of the parties involved in the design, erection and use of the specialized equipment.  During recovery efforts, Haag assisted in the design/evaluation of a new cableway system, erection and load testing.  The Haag team was assigned to the project from collapse on September 15, 2006 until the connection of the arches in 2010. 

The Hoover Dam By-Pass Bridge was sucessfully completed after this set-back, and officially named the “Mike O’Callaghan–Pat Tillman Memorial Bridge”. Opening ceremonies were held on October 19, 2010. The bridge has been a vital to improving traffic on Interstate 93, between Phoenix and Las Vegas and between the United States and Mexico, ever since.

Hoover Dam