The death two months ago (July 2006) of a woman travelling through the I-90 highway tunnels in Boston has initiated the most far-reaching probe of the project to date. State and Federal inquiries, including an investigation that could lead to charges of negligent-homicide, have resulted in subpoenas being served on several companies involved including; the project design, construction and program management JV of Bechtel and Parsons Brinckerhoff; the detailed designer of the tunnel involved, Gannett Fleming; and its contractor, Modern Continental.
Failing anchor bolt
Political fallout includes the resignation in August of Matthew Amorello, Chairman of former project operator, the Massachusetts Turnpike Authority (MTA), and appointment through emergency legislation of the Governor's Office as controller of the quasi-independent MTA - something that Governor Mitt Romney has been seeking since he came to office three years ago. There is also political haggling over individuals selected as leaders of different investigations amid concerns over conflicts of interest.
The fatal accident occurred at 11pm, Monday evening, July 10, when panels of the tunnel's suspended ventilation duct ceiling fell onto a vehicle, killing 39-year old Milena Del Valle of Boston. The car was traveling on the I-90 approach to the Ted Williams immersed tube tunnel across Boston Harbor towards Logan Airport and was within a few hundred feet of leaving the tunnel into a short open cut section ahead of the Ted Williams portal. The driver managed to crawl from the wreckage. The I-90 underground highways were closed immediately and indefinitely while the accident was investigated.
Traffic management: Since the accident on 10 July (2006), the I-90 tunnel connecting the I-93 and the Ted Williams Tunnel (TWT) has remained closed in both directions. As of 21 August (2006) there was no forecast for when it might reopen. The I-93 tunnels were not closed although the alternative fixing system of their ceiling panels was also under inspection. TWT eastbound was closed as a result of I-90 being closed and westbound traffic was slowed due to inspection lane closures.
Various contractors working on retainers have been carrying out inspection and repair works in the I-90 connector tunnels. TunnelTalk was told tests of bolts in the eastbound tunnel were complete, tests were progressing in the westbound tunnel, and design of works to reinforce the ceiling panel system in the I-90 tunnels was ongoing.
The I-90 underground highway would normally carry some 200,000 vehicles/day.
Initial findings revealed that epoxy-resin anchored bolts holding tie rods and flanges that support the precast panels of the suspended ceiling had failed, causing four 4m-wide x 2m-long x 150mm-thick, 3 tonne reinforced concrete panels to fall. Subsequent examination revealed that several more bolts in the I-90 tunnels were suspect or close to failing.
Epoxy anchored bolts were used as part of the suspended ceiling design in the I-90 Big Dig cut-and-cover tunnels and in the Ted Williams immersed tube tunnel (TWT). Heavier precast concrete ceiling panels were adopted for the Big Dig tunnels as a value engineering change from lightweight panels used in the TWT.
"The TWT panels are about one third the weight of the I-90/I-93 panels", said Jonathon Carlisle, Press Secretary of the Massachusetts Executive Office of Transportation. He said "the bolts for the ceiling hangers in the I-90 tunnels are bigger and deeper than in the Ted Williams Tunnel" but that, because the Massachusetts Department of Transportation had only recently taken over responsibility for the highway system from the MTA, "we are not clear on the history of the project. When more suspect bolts were found in the I-90 tunnels than in the TWT, the concern was for a systemic problem in the I-90 tunnels."
A different system of steel-to-steel fixing was used for the Big Dig I-93 tunnels, with the steel receivers embedded in the top deck cut-and-cover concrete slab during casting.
Rising costs for installing the ceiling panel system in the Ted Williams Tunnel were blamed in an inspection report on "poor design specifications, inadequate management of construction, improper load testing, and unauthorized deviations from specification". The report found that bolts drilled into heavily reinforced concrete were being cut short to avoid rebar, and that resin bonds had failed pull tests.
The Ted Williams Tunnel was built earlier than the Big Dig cut-and-cover tunnels and opened in 1995/96. The mostly cut-and-cover Big Dig tunnels of the I-90 and the I-93 (to replace the old elevated Central Artery highway underground) were completed in December 2004.
The Big Dig took 15 years to complete, twice as long as originally estimated, and has cost $14.6 billion, more than double the 1990 $6 billion start-of-construction estimate and five times the near $3 billion original environmental impact statement estimate of 1983.
Big Dig indictment - December 2007
The supplier of the epoxy I bolt fixing compound blamed for the fatal Big Dig Tunnel ceiling collapse has been charged with one count of involuntary manslaughter. Action against Powers Fasteners Inc is the first criminal indictment following the July 2006 accident.
The charges stem from a July 2007 report by the National Transportation Safety Board (NTSB) blaming the use of fast-set instead of standard-set epoxy for the failed bonding of bolts that anchored the suspended ceiling system in the tunnel. The NTSB said Powers Fasteners provided "inadequate and misleading information" about the potentially deadly consequences of using fast setting epoxy to secure the ceiling bolts.
In a statement, Jeffrey Powers, the company's President said they were "stunned, beyond belief" at the indictment, adding that the company had filled an order for standard set epoxy and was unaware that the fast-set had been used instead.
The Board's report made no mention of an earlier investigation charging that anchor bolts had been cut to fit holes drilled shorter to avoid rebar in the heavily reinforced concrete of the underground structure.
The NTSB report also blamed ceiling designer Gannett Fleming for failing to specify the appropriate epoxy, and tunnel builders Modern Continental, and project construction managers Bechtel/Parson Brinckerhoff, for failing to determine that the wrong material was being used when bolts showed evidence of coming loose during construction. The Massachusetts Turnpike Authority (MTA), the owner of the underground highway, was faulted for not instituting a timely tunnel inspection program that would have revealed the problem.
Massachusetts continues its investigation and the victim's family has filed a wrongful death lawsuit.
Thank you for taking the time to share your thoughts and comments. You share in the wider tunnelling community, so please keep your comments smart and civil. Don't attack other readers personally, and keep your language professional.
Your feedback has been submitted successfully and is currently under review.