The Massachusetts Turnpike Authority yesterday approved an additional $6 million to pay for Big Dig repairs, increasing the price tag from last summer's fatal tunnel ceiling collapse to $31 million -- with more potentially to come.
"I sitting here today can't guarantee to the board that there wouldn't be another increase requested," Big Dig project director Michael P. Lewis told Turnpike Authority board members, who unanimously approved the request.
State transportation officials said the rising cost reflects labor-intensive repairs to the massive tunnel system's fundamental design, which engineers found necessary to ensure public safety after Milena Del Valle of Jamaica Plain was killed in the July collapse in the Interstate 90 connector tunnel.
Lewis said the additional $6 million would enable workers to finish the major remaining repairs within two weeks, as well as any subsequent repairs ordered by state transportation officials after final inspections.
But some Turnpike Authority board members were skeptical.
"It's just growing and growing and growing. Is it coming to an end?" asked Mary Z. Connaughton of Framingham.
About a month after Del Valle's death, Big Dig officials sought and received $15 million for fixes, but warned that the amount was a preliminary estimate. In December, the turnpike authority board approved another $10 million at the request of Big Dig officials.
The Turnpike Authority board's chairman, John Cogliano , who presided over the aftermath of the tunnel collapse as transportation secretary under former governor Mitt Romney , said any initial estimates made on repair costs were based on limited information.
"If you go back to July, we didn't know," he said.
"We didn't know what the problems were. I would be hard pressed to come up with an estimate back then."
The investigation into the tunnel collapse uncovered widespread irregularities in the bolts that secured ceiling panels throughout the tunnel system, with the problem most severe in the I-90 connector tunnel. The repair work included the installation of about 50,000 new bolts in the tunnel and a more durable support system that replaced the old epoxy-secured bolts. The westbound portion of the connector reopened Dec. 24, while all lanes of the eastbound side were opened to traffic on Jan. 14. In addition, several on ramps throughout the Big Dig system were closed for periods while repairs were underway.
Lewis told board members that the unexpectedly high price tag for repairs stems in part from the complexity of simultaneously conducting repairs and redesigning parts of the tunnel system, a dual-track process forced on work crews by pressure to open the tunnels quickly after the accident. In addition, Lewis said, other problems uncovered during inspections drove up costs.
Lewis said there is still significant work to do in the still-closed northbound Interstate 93 high-occupancy-vehicle tunnel. He said minor repairs are also needed on one I-90 connector on ramp, as well as on several massive jet fans suspended from the ceiling of the tunnel.
Lewis said 90 percent of the repair money has been spent on labor, with the rest going to construction materials. The money has come from the state government's bond account. Attorney General Martha Coakley is contemplating a lawsuit against Big Dig contractors to recover the money.