Massachusetts Department of Transportation (MassDOT) has said that design errors mean that there will be a year’s delay in the completion of a US$81.8 million bridge project in the US city of Boston.

The delay to the I-90/Commonwealth Avenue Bridge is due to design errors on the part of Walsh Construction’s engineering firm HDR Inc, said MassDOT.

The errors have led to fabrication delays in steel girders being used for the new superstructure. Closures of local roads and rail services had been planned during July and August this year to allow the installation to take place but the components will not be ready in time.

MassDOT has now decided to postpone the two closure phases of the project by one year to July and August of 2017 and 2018, respectively. Walsh Construction will forfeit the US$7.2 million incentive tied to successful completion of the 2016 closure phase.

In a statement about the postponement, Walsh Construction said: “During the final bridge design quality control checks, two issues related to the design of the new structural steel girders were encountered that required revision and modification to the final steel girder design. As a result, the fabrication of the new steel girders is not able to be conducted as originally contemplated to meet a shutdown in the summer of 2016. However, in conjunction with MassDOT and our designer, we have resolved these issues and look forward to successfully completing the first phase of the project in the summer of 2017.”

The Commonwealth Avenue superstructure replacement project involves building a new bridge to carry Commonwealth Avenue and the MBTA Green Line over a commuter rail line and the I-90 highway.

Comonwealth Avenue Bridge

Last year, Walsh was awarded the contract with a bid of US$81.8 million and was given notice to proceed in June 2015. In January this year, MassDOT was notified by Walsh that design errors on the part of its engineering firm of HDR have resulted in fabrication delays, and Walsh Construction would be unable to meet this year’s scheduled closure dates.

The contract called for restricted closure durations for each of the transport facilities that are affected: 18.5 days for Green Line, 17.5 days for Commonwealth Ave, 9.5 days for the I-90 crossover and 49 hours for commuter rail. The contract required these closures to take place within two closure windows, 21 July to 29 August this year and 27 July to 28 August 2017. These dates were  chosen because the Boston Red Sox would be out of town, Boston University would not be in session and because data revealed that traffic volumes are approximately 15% lower in the summer months compared with the fall.