Let’s cut right to the moral of the following story: if you’re doing a partial demolition of a 100-year-old bridge, and the work involves cutting work beneath the bridge deck, it’s important to have a qualified engineer perform an analysis, before parking a 45-ton-excavator on the deck (above where the supports have been weakened). Should you fail to do this, you may find that the structure retains too little strength to bear the weight of the equipment.
In Secretary v. Francis J. Palo, Inc., the employer, Palo, was the general contractor on a Pennsylvania DOT contract for a demolition and construction project on a state road n Elk County, Pennsylvania. A segment of the project, a bridge over a creek, partially collapsed beneath the weight of a 45-ton CAT excavator that the contractor had parked on the bridge’s closed, northbound lane that was being demolished.
The span in question had been built in 1912, and PennDOT had cautioned bidders on the project that no design drawings for it were available. The bridge had one traffic lane, plus a sidewalk, running in each direction. Beams spanning the bridge in the north-south direction were fixed into abutments at each end. Just above the abutments at each end, the beams were interconnected through a diaphragm.
The beams were cast-in-place concrete, in the shape of an arch, with the center of each beam about two to three feet shallower than the ends. The bridge was identifiable on sight as a “cast-in-place, rigid, fixed beam, arch bridge.” The bridge’s greatest strength was at the ends of the beams, not at the center of the span.
The employer’s demolition plan, accepted by PennDOT, called for the bridge to be demolished and rebuilt in phases. Demolition was to be carried out by cutting the concrete away from the supporting abutments on both sides. A longitudinal cut was made down the center of the bridge roadway deck, separating the north side from the south side. This allowed the southbound traffic lane to remain open, during the partial demolition and reconstruction of the bridge’s north side.
Following the initial cut, workers focused on demolishing the north side of the bridge, by cutting the supporting abutments at each end.
This cutting work was done by a subcontractor, and Penn
DOT had an employee onsite, and engaged an engineering firm to inspect the worksite. However, as the general contractor, the employer was responsible for worksite safety.
It could be argued that PennDOT was somewhat at fault, as it did not assign the bridge a specific weight limit before the project began, and nothing in its documentation specified whether the bridge could withstand having a piece of mechanical equipment, weighing some 45 tons, being used or parked on it, particularly after the cutting work began.
However, PennDOT did specifically caution bidders to verify the information it provided, and the OSHA standard under which the employer was cited effectively assumes a hazard, as it prohibits the use of mechanical equipment, without first ensuring that the working surface has sufficient strength to support the imposed load.
While the cutting work beneath the bridge deck was ongoing, the CAT was brought onto the bridge, and was used on that day, and the next following day, to remove rubble created by the demolition process. On the third day, the CAT was parked on the closed northbound traffic lane. The cutting subcontractor had already made several cuts to the supporting abutments located beneath the bridge deck. One of the abutments had been vertically cut, and the subcontractor was making vertical cuts to the second abutment in the north lane.
Suddenly, the employer’s super noticed that the deck on the north side of the bridge was lower than it had been, and tried to order everyone off the bridge. Unfortunately, this condition was detected too late, and the north side of the bridge collapsed into the creek, injuring four workers.
The employer contested the citation, conceding, however, the elements of applicability of the standard, violation of its terms, and employee exposure). The sole basis for the contest was that the employer denied actual or constructive knowledge of the hazard.
OSHA’s expert engineer testified at the trial that, as an experienced demolition contractor, Palo should have recognized from the start the character of the bridge as a cast-in-place, arched, rigid frame beam bridge. Because of its design – the beam ends being deeper, and supported by the diaphragm and abutment – when a load was imposed on the bridge, its path went to the end of the beam, where the strength was.
As OSHA’s expert testified, the horizontal and vertical cutting work at the bridge’s supporting ends — affecting the abutments, diaphragm, and beams — had the effect of changing the bridge’s structure to that of a simple span bridge. This change compromised the bridge’s load-carrying capacity. Unlike a fixed rigid frame bridge, a simple span has a hinged connection at each end, for a fixed connection. As such, a bridge functioning as a single span bridge does not continue to distribute loads onto the abutments. Thus, its ability to support its own weight and that of a superimposed load having been undermined by the contractor’s having severed the bridge’s support mechanisms (abutment, diaphragm, and beam) from one another, the bridge collapsed beneath the weight of the excavator.
As underscored in the Administrative Law Judge’s decision affirming the OSHA citation and penalty, the employer called no expert witnesses to rebut OSHA’s engineer. It had to admit it had taken no specific actions to ascertain whether the bridge would be able to continue to support the excavator’s weight after it was cut multiple times, including through both supporting abutments.
Palo made what the ALJ found to be an insufficient attempt to establish due diligence, by arguing that it had reviewed information PennDOT provided as part of the bidding process, “inspected” the bridge, worked according to a demolition plan, and was an experienced contractor.
The employer’s review of information from PennDOT was insufficient, as there was nothing in that information that specified that the bridge could withstand having a 45-ton piece of equipment being used or parked on it. Palo’s “inspection,” the ALJ found, did not include an engineering analysis prepared by an engineer, nor did any other documentation provide any analysis supporting the conclusion that the bridge would withstand the CAT’s eight, once the abutments had been cut.
The mere fact of proceeding according to a demolition plan, the ALJ found, did not suffice to establish due diligence. Palo’s demolition plan did not discuss using the CAT on the bridge deck at any time, much less after multiple cuts had been made to both abutments. Palo did not request any inspection reports, or other information from PennDOT, to ascertain the bridge’s structure and strength, or obtain an engineering survey on its own.
All in all, the ALJ found, the record lacked evidence from which it might be concluded that anyone else involved with the project agreed with Palo’s assertion that it performed reasonable diligence, or agreed it was reasonable to move and leave the CAT on the bridge, after the cutting began.
The notion that Palo’s “experience” established due diligence was rejected by the ALJ, as most of that experience was with bridges with a different design than the one that collapsed, and the employer’s decision-makers, none of whom were professional engineers, took no specific action to verify that the bridge would be able to support the CAT’s weight after both supporting abutments had been cut.
If you are in the business of demolishing and reconstructing bridges, it should be obvious that a formal engineering evaluation of your demolition plan should be done by a qualified professional engineer, before any demolition gets underway. As even many “civilians” are aware, thousands of bridges in the USA remain in use, decades beyond their life expectancy. The need for engineering advice is even more pronounced when the project calls for work on a bridge of an older, uncommon, or unfamiliar design, or where it will involve equipment much larger than any in use when the bridge was first constructed.