Tests on a 25-foot, high-strength steel rod that secured the base of a tower on the eastern span of San Francisco’s new, $6.5 billion Bay Bridge recently showed widespread cracking, according to the San Francisco Chronicle.
This is bad news for the 2,049-foot, two-span, self-anchored suspension bridge that was once one of heavy civil construction’s most decorated and talked about projects. Rust and microscopic cracking were found after one of the 424 high-strength steel rods, intended to keep the tower from being damaged in an earthquake, was removed for testing last year. The tests were needed after the tower on the eastern span listed too far to one side and had to be “crow-barred” back into its intended position by being pulled with cables from nearby Yerba Buena Island.
What’s even worse is that the reason the test was necessary in the first place was because the California Dept. of Transportation (CalTrans), the state agency that functions as the owner of the bridge, was worried that water exposure on the bottom of the steel rods led to the listing problem. The problem was even worse than they suspected, as the steel rod tested showed signs of corrosion on the top of the road, not just the bottom where it was exposed to water and corrosive hydrogen.
The bottoms of the rods were exposed to water because not enough grout had been pumped into protective sleeves designed to keep them dry once they were installed, CalTrans officials told members of the bridge project oversight committee. The corrosion at the top of the rod suggests that the problem with the rods goes beyond the areas exposed to water.
How did this happen? How can such a huge public works project be susceptible to these mistakes? Failure to control supply chain standards.
CalTrans Chose to Waive its Own Rules
According to the Chronicle, CalTrans decided to waive its own rule against using high-strength galvanized-steel rods and bolts on bridges when it came to construction of the eastern span during the design phase of the project in 2003.
Galvanization — a process by which the rods are coated with molten zinc — is understood as a threat to high-strength steel. The process carries the risk the rods can be exposed to hydrogen. Caltrans decided, however, that the extraordinary seismic demands placed on the eastern span, because of its unusual self-anchored design, required high-strength steel. CalTrans specified precautions to avoid hydrogen contamination during processing, but many of those steps were never followed.
The Buy American provisions, for instance, for sourcing of federal projects were not followed.
Lack of Oversight
Caltrans belatedly learned it had no record of overseeing the manufacturing process or testing the tower rods before they were installed. The tower rods had been bathed in hydrochloric acid before being delivered to the bridge, a major no-no that CalTrans had specified against because it could expose the rods to hydrogen.
The rods were scraped en route from the Tennessee plant where they were galvanized in 2007. At a stopover in Texas, workers spray-painted the scrapes and other damage to the galvanization layer. Any damage to the threads from the scrapes could foster the cracking happening today.
Before the bridge opened in 2013, rust and other signs of corrosion had been visible on the rods in 2011, but that no one had checked them further.
Scope of Risk
The general contractor of the massive project, a joint venture of American Bridge and Fluor Enterprises, has denied responsibility for any of the supply problems for the steel rods and for a previous problem with cracked bolts and, if the stories about shipping problems and galvanizing of the rods are truly the cause, they do seem to be issues that are outside of a builder’s normal scope of work and are very much supply issues. It’s a cautionary tale that project owners need to verify their own standards are being met and their own supply chain practices are being implemented during construction –not after.