Fundamental design flaws in the concrete foundations of an elevated reversible-lane toll road in Tampa have been cited for the problems that have delayed completion of the $350-million Lee Roy Selmon Crosstown Expressway. The owner, Hillsborough County Expressway Authority, sent the designer URS Construction Services, a division of San Francisco-based URS Corp., a letter of indemnification on Aug. 27 asking for a remediation plan.
On April 13, a pier collapsed, dropping 11 ft and causing two sections of roadway to buckle. On July 6 inspectors discovered that another pier had settled 1.3 in. Acceptable design margins allow bridge piers to sink no more than 1 in. during construction (ENR 8/2, p. 13). The authority hired Ardaman & Associates, an Orlando-based engineering firm, to oversee testing of the existing piers and the locales of future piers for the project.
Basically, what were looking at, or the heart of it, is the foundations were found to be defective, says PerryDawn Brown, spokeswoman for the authority. The numbers just didnt gel when our independent geotechnical firm actually went over the numbers. Florida Dept. of Transportation engineers took a second look at Ardaman & Associates calculations. They both found that the foundations were faulty, Brown says. The numbers just werent correct.
According to the findings, URS engineers overestimated the strength of the limestone layer supporting the piers and decided it was safe to build shallower foundations. Shafts for the piers reached 70 ft deep. Tallahassee-based Figg Engineering, which designed the elevated portion of the road, had requested deeper foundations originally. Foundation sites were tested by core borings between 80 and 150 ft that yielded a cross-section for examination. The borings extended past the lowest point where the foundations were to reach but did not go deep enough to uncover problems.
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This is the biggest engineering firm in the world, says Pat McCue, executive director of the authority, referring to the question of why the URS design plans had not been double-checked. They signed and sealed this thing. They have advised my board and bondholders that they have made proper engineering decisions. There was no reason to doubt them."
Completion of the project, being built under a $145-million contract by PCL Civil Constructors, a division of PCL Enterprises, Edmonton, could now be pushed out to 2006 from 2005. Costs of repairing the 197 piers loom as high as $70 million. "Were sending [URS] a letter of indemnification and from the receipt of the letter they will have seven calendar days to respond with a remediation plan for what they plan to do, Brown says. Of course after that there will be a negotiation period [as to] whether or not we accept it. We plan to vigorously go after the responsible party. In this case we feel, at this point, it points to URS. So well look to recoup the funds from them and we hope that well be able to work with them in finding a solution, and that theyll be cooperative in working with us toward a solution. If not, then of course, litigation may follow."
A spokesperson in URS' New York City office says the firm does not comment on potentially litiguous situations.
