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The nearly re-constructed Fourth St. Bridge a piece of Dr. Frankensteinlike patchwork engineering whose design revolves around accommodating a huge, decorative fiberglass faux counterweight is a potential death trap, says the co-owner of the company that re-built the drawbridge.
In the deadly scenario imagined by Curtis Mitchell, co-owner of Mitchell Engineering, the bridge's true counterweight, a million-and-a-half pound block of iron-ore-infused cement hidden in a chamber underneath the bridge, is too heavy for the steel pivots that support the bridge span. One day, while the bridge is being elevated to make way for a passing boater, Mitchell imagines the steel supports around the pivot might strain, then buckle. The span could crash down to China Basin Canal, crushing watercraft underneath.
"One of the concerns is that something might happen, and they will blame us, and that's not right," says Mitchell, as he gives me a tour of the new bridge, one block southwest of the Giants' ballpark. "That's why I'm willing to go on the record and draw attention to it. Because it's just not right."
Waterborne San Franciscans really needn't begin donning hard hats, however. Mitchell hasn't done any meaningful engineering analysis to back up his assertion that the bridge is poised to collapse. He has made his claim as part of an argument that the city owes him money for cost overruns and delays, because, he alleges, the Department of Public Works gave him badly designed plans.
Mitchell's own staff engineer assigned to the bridge, meanwhile, does not feel comfortable repeating his employer's assertion that it is unsafe because the bridge and its counterweight are too heavy.
"I have my own little reputation to protect," he says, in declining to repeat Mitchell's claim about the bridge weight.
So why does Mitchell make such an alarming, confrontational, and spurious-seeming assertion?
The answer to that question lies at the heart of a civil engineering crisis that threatens to cost San Francisco many billions of dollars in construction and materials costs, as the city struggles to find contractors willing to undertake massive projects such as bridges, electricity infrastructure, and the retrofit of the Hetch Hetchy water delivery system. If something isn't done to change the system, the Hetch Hetchy rebuild price tag could escalate from $4 billion to many billions more.
As extreme as they seem, Mitchell's statements are prosaic in the context of the city's conflict-based system of hiring and overseeing private companies to construct public works. Critics both in and outside city government describe a system where sometimes flawed engineering plans are used as a battleground for financial advantage, as the city and private contractors fight over who should bear the expense of costly mid-project design changes. Rather than rapidly and amicably resolving such problems, the city has gained a nationwide reputation for allowing design problems to repeatedly explode into lawyerly disputes, costing contractors, and the city, millions of dollars in delays and cost overruns.
The system's resulting reputation for generating hostility has gotten so bad that civil engineering firms now routinely decline to bid on city projects, a situation that threatens to delay billions of dollars worth of scheduled work on the Hetch Hetchy water system, electricity generation facilities and other projects, adding many billions in additional city costs.
"If we do not shape up our contracting procedures, there is no telling where this thing could go. Things could go through the roof," said San Francisco Public Utilities Commission President Richard Sklar in an interview. "The number could be infinite."
Last Tuesday Mitchell took me down a narrow stairway into the barn-sized cement chamber below the bridge. It houses an only slightly smaller, iron-ore flecked rectangular mass of concrete that represents the latest in a series of engineering debacles that set the bridge project back more than a year, leading the city and Mitchell to dispute more than $10 million in costs.
Drawbridges are typically constructed by balancing a bridge's span opposite a heavy counterweight astride a pivot, similar to a teeter-totter. In this way, a relatively tiny force is required to raise and lower the platform.
In a classic design such as the original 1917 Fourth Street span, the mammoth weight hangs in the air over traffic, lowering to the ground every time the bridge makes way for passing boats. In the re-constructed bridge, the weight was positioned underground, so as to be safer in the event of an earthquake. But to keep the appearance of the old bridge, sculptors, who do much of their work creating floats for Disneyland, were hired to construct a hollow fiberglass duplicate of the old weight to hang in public view. The underground location of the real weight created new problems, however. Because it hung at a different angle than the old weight, it had to be heavier in order to easily lift the bridge span. But it had to remain the same size, meaning Mitchell had to buy extra heavy cement containing iron ore.
"See how the flecks shine in the light?" asked James Hawkes, the bridge's project manager, as we made our way through the narrow space between the weight and the chamber wall.