A structural beam may have been the first component to fail in last month's partial collapse of a bridge under construction in Old Town, according to the Maine Department of Transportation, although investigators have not yet determined the precise cause.
The collapse happened Aug. 13 as construction crews were pouring concrete for the deck of the new northbound Llewellyn Estes Bridge. The span was still being built and had not yet opened to traffic.
Three workers were injured in the incident. One suffered a broken ankle, while two others were treated for minor injuries.
Preliminary Findings Point to Beam Failure
MaineDOT said its investigation so far indicates that an outer beam along one side of the bridge may have buckled during the concrete pour. That failure could have placed additional stress on adjacent beams, causing them to fail in rapid succession and resulting in the partial collapse of the bridge span.
The agency cautioned that the finding remains preliminary and could change as additional evidence is examined.
Engineers are now conducting more extensive testing and computer modeling in an effort to reconstruct the sequence of events and identify the underlying cause. Investigators have been collecting project records, reviewing available data and documenting conditions at the collapse site. Materials are also being prepared for forensic examination.
MaineDOT has brought in specialists from the Federal Highway Administration's Turner-Fairbank Highway Research Center to assist with the technical investigation.
The removal of the collapsed material could provide investigators with additional clues. The project's contractor is developing a plan for clearing the debris, and MaineDOT said information uncovered during that work could help engineers determine how and why the bridge failed.
Temporary Bridge Remains Open
The collapse did not damage the temporary bridge being used to carry Stillwater Avenue traffic, MaineDOT said. That two-lane structure remains in service and is considered safe, allowing traffic to continue using the temporary crossing while work on the project remains suspended.
For now, the department does not have an estimate for the financial cost of the collapse or a clear indication of how significantly it will delay the project.
MaineDOT said a revised construction schedule will be prepared after investigators have a better understanding of the failure and determine how the project should proceed.
The Llewellyn Estes Bridge project is intended to replace two bridges carrying Stillwater Avenue across the Stillwater River in Old Town. MaineDOT said it will provide additional information as significant findings emerge from the ongoing investigation.
