New findings have identified a further 20 areas of concern with the troubled Cambridge guided busway scheme.
A report, published in November last year by Capita and Atkins on behalf of Cambridge County Council, concluded £36.5M of repairs were needed in addition to the £8M already spent on the six year old line. At the time, the council said it was hoping to recoup the cost of the repairs from the contractor who built the line, Bam Nuttall.
Smarter Cambridge Transport – comprising an “impartial group of local people” – has now prepared a detailed review of the reports carried out to date, listing a further 20 areas of concern, which it claims have not been previously identified – although it said these may overlap with ongoing work carried out by Capita and Atkins looking into the issue.
The body said one of its main concerns was whether the problems were due “in part not to construction defects, but to inherent design flaws that repairs alone cannot fix.”
It is now asking the council to conduct an open re-evaluation of the busway, independent of action taken against the contractor, comparing the cost and safety implications of it to a light rail alternative.
In the November report, movement of the bearing pads on which the guideway beams rest was blamed as one of the most notable defects, resulting in a number of instances of “steps” appearing in the guideway.
The majority of the new report focuses on additional research it wants to be carried out around some of the key issues raised by the work already carried out by Capita, such as asking if an assessment had been made of ride quality, and evidence that heave and subsidence were caused by tree roots alone.
Among other concerns, it also went on to question to what extent the geology had been examined as a possible explanation for the subsidence and heave problem, and it also questioned the interaction between shallow foundations, the surrounding soils and changing water table.
“The report published by Capita in November 2016 indicates that the design of Cambridgeshire Guided Busway is deficient in several respects,” said the Smarter Cambridge Transport. “The investigations upon which the report is based, were conducted within five years of the Busway going into service in August 2011.
“We believe there are significant grounds for concern about the integrity of the busway in its present form. There is a lack of data in the public domain to reassure us.
“Although some of the issues of the last five years may be put down to initial settlement, there is little to indicate that movement has stopped. The geology is varied along the route of the Busway, and will continue to change as development continues close by. Establishing secure foundations has proved difficult in the past, and Capita confirm that even rebuilding with revised foundation design carries no guarantees.”
The transport body now wants to see “the whole concept” of a kerb-guided column-and-beam busway reviewed, “particularly in the light of advancing guidance technology”.
Bam Nuttall declined to comment.