The scheme includes a new floating bridge and six-lane highway. The Washington State Department of Transportation (WSDOT) annoucement of the reduced costings cited a good bid environment and other factors.
In addition, WSDOT has outlined steps to avoid a repeat of spalling issues experienced in elements of the bridge pontoon construction already under way.
Documents have also been finalised documents for a US$300 million federal loan that will fund design and construction of the next portion of the SR 520 project – a westbound bridge between the west-end landing of the new floating bridge and Montlake. The updated estimated cost for the 20.6km corridor is US$4.128 billion, compared with the legislative budget cap of US$4.65 billion. With the new federal loan, the unfunded portion of the programme is US$1.4 billion, down from an estimated US$2 billion in 2010.
Transportation secretary Paula Hammond has instituted personnel and organisational changes for the pontoon construction project. The aim is to ensure WSDOT has a strong project delivery team, improved coordination and stronger oversight of the construction contract. She has also re-convened an expert review panel to conduct additional analysis of pontoon design, repairs and construction management processes.
The organisational changes come as a result of a thorough internal review, ordered by Hammond, of the first cycle of pontoon construction in Aberdeen to fully understand the cause of concrete spalling and more-than-expected cracking. WSDOT’s pontoon design included an error in the post-tensioning duct alignment that is determined to have caused the spalling in one pontoon during tensioning, making repairs necessary. The expert review panel was brought in immediately to evaluate the pontoon cracking and spalling repair and design modifications.
