We have received an update from Gloucestershire Highways about the road closure at Prison Copse Wall behind the Old Prison, also known as the Old A40.
Further to approval at the Capital Programme Meeting this week, funds have been set aside to undertake a Ground Investigation along the site of the Prison Copse Wall this financial year. The Ground Investigation will be designed to clarify the failure mechanism at the site and help to confirm the type of solution best suited.
Unfortunately without this information the team of engineers are unable to ascertain if this is a structural failure of the wall itself or a rotation slip with a failure in the land beneath the wall (geotechnical failure). Without this information the type of treatment applied to the site can not be established. The ground Investigation will involve the coring of boreholes around the site to establish the ground make up and geology. This is a specialist survey which will unfortunately take time to arrange and complete. All samples gathered will be subject to lab tests before a full report into the results of the investigation are published. The results will feed into an option report and outline design subsequently undertaken.
The results of this investigation will allow us to make informed decisions about the nature of the failure and the suitability of any funding allocation for a future scheme to remedy the retaining structure. That said, funding at this location will need to be priority assessed against other similar schemes. The budget available annually for Geotechnical work is £1million; however this funding does not stretch very far and on average only two large Geotechnical schemes a year are progressed through to completion on this budget. A similar figure is set aside for Structures Schemes, which caters predominately for the County’s Bridges, but with Bridge works on average costing between £50k and £100k this doesn’t stretch to many of the 810 bridges the County is responsible for maintaining.
Our team of Geotechnical and Structural Engineers continue to monitor this site and are concerned about the stability of the wall. The report on 26th November 2015 stated ‘The defective carriageway could potentially be at risk from a catastrophic failure if the wall collapses’; as such we have no option to close the road above the structure to insure the safety of road users. Subsequent inspections have noted further movement in the wall. As a responsible Highway Authority we can not let the public use this section of the highway when there are such significant safety concerns.
I understand the road closure has caused inconvenience to local residents, however the diversion in place is relatively minor and minimal properties are affected. With all of the above taken into consideration I hope you can see that we are taking all the necessary steps to resolve the situation but defects such as this do take considerable time to remediate and we do not anticipate the road will be re-opened in the foreseeable future.