§ Dr. Owenasked the Secretary of State for Transport what investigations into structural decay caused by alkali-silica-reaction on concrete bridges on the A38 Exeter to Plymouth road he has commissioned; what those investigations have revealed; and what has been the cost of employing consultants to conduct the investigations.
§ Mrs. ChalkerConsulting civil engineers, Mott Hay & Anderson, have recently been appointed to carry out all necessary examinations and tests on concrete bridges on the A38 near Plymouth including the Marsh Mills viaduct, Plympton Hill underbridge and Voss Farm overbridge, where the condition of alkali-silica reaction has caused cracking. The investigation includes monitoring and classifying the extent, nature and effect of deterioration. The consultants will report initially on the present strength of each structure, and recommend immediate remedial works, further monitoring to determine the rate of deterioration and any protective treatments. After further tests, a final report will be submitted giving recommendations for ensuring the safety and long-term life of each structure. This appointment follows investigation work by Devon county council, as agent authority for the Department, in monitoring the development of cracks first discovered in routine bridge inspections about two years ago. In the consulting engineer's survey, cracks have been discovered in sub-structures and the investigation is continuing. The estimated cost of employing the consulting engineers is £60,000.
§ Dr. Owenasked the Secretary of State for Transport if he will estimate the cost of (a) repairing and (b) demolishing and replacing the bridges on the A38 affected by alkali-silica-reaction.
§ Mrs. ChalkerThe cost of(a) repairing, or (b) demolishing and replacing bridges if this proves to be necessary, will not be determined until the reports have been completed and the full extent of the problem is known.
§ Dr. Owenasked the Secretary of State for Transport when work to remedy the damage to the bridges affected by alkali-silica-reaction on the A38 will commence.
§ Mrs. ChalkerSome remedial work has already been carried out at Voss Farm overbridge in temporary strengthening to one column in the central reserve. Further work on this and other bridges will be carried out as and when necessary.
§ Dr. Owenasked the Secretary of State for Transport whether other concrete bridges in Devon and Cornwall have been surveyed to discover further cases of damage from alkali-silica-reaction; which bridges have been thus identified; what is the extent of the remedial work required; and what is the date and cost of conducting the remedial works.
§ Mrs. ChalkerEleven other trunk road bridges in Devon, built with similar materials, are potentially susceptible. They will be kept under observation, but at the present time their condition does not necessitate any remedial work. No similar problems have been identified in Cornwall.
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§ Dr. Owenasked the Secretary of State for Transport if he will make a statement about the danger to public safety from continuing to travel over bridges affected by alkali-silica-reaction on the A38.
§ Mrs. ChalkerThere is no danger to public safety and the bridges are fully open to traffic, but the situation is being carefully monitored.
§ Dr. Owenasked the Secretary of State for Transport what remedial action will be taken to prevent any immediate risk to public safety on the A38.
§ Mrs. ChalkerAction has already been taken to strengthen one column at Voss Farm overbridge. In the light of the consultant's findings, measures are being taken as necessary on this and other bridges to prevent risk to public safety.