It is now two months since the water main burst on Alfreton Road and understandably people are asking what is being done to get the road open again. Behind the scenes there has been much work taking place on what has proved to be an enormously complex situation.
We wanted to update you on what has happened so far, and where we are now.
On Thursday 9th August, a 15 inch Severn Trent Water (STW) water main burst, flooding the road and railway track nearby.
This was an extremely serious event; it caused major damage to the road surface, creating a large void beneath the surface of the road. Water also ran through the structure of the Grade II listed bridge, and onto the railway lines.
The first issue was the burst main, so following an initial inspection, a full site meeting took place with all the utilities companies who have services going through the bridge to inspect their damaged equipment.
At this stage, it was established that there were serious concerns with the structural integrity of the bridge and that a detailed investigation was required.
Working with STW work was carried out to remove damaged pipe-work, and prepare for work on the road, and the reinstatement of the burst water main.
Due to the Derby Resignalling Project , Network Rail is completing a huge amount of work in the area making access more difficult than usual, however we have worked closely together on this issue and were able to carry out our first detailed inspection of the bridge from the track level on Tuesday 28th August.
The initial results showed that the bridge had a large volume of water inside the structure. This came from the road when it initially flooded, but was running through the bridge for several days. As the water leaked out, this dragged with it brickwork and debris from the bridge.
From this, it was clear that damage was not just to the road, but to the internal structure also, and further testing and inspection would be required, in order to understand the full scope and scale of damage to the bridge.
In early September, access to the railway was agreed with Network Rail, and a second, more intrusive inspection of the bridge was carried out taking samples to establish the condition of the brickwork and fill material.
Results of this showed that the structure as a whole was sounder than original inspections indicated, however geotechnical investigations (to the soil, rock and brick of the bridge) began to give us a better picture of what damage had been done.
Due to the water leaking from the bridge, a number of holes, or voids, were created inside the bridge, and so in mid-September, a Ground Penetrating Radar (GPR) survey was carried out to try to map the location of voids.
While this was happening, STW completed their work to install new valves on either side of the bridge and sleeve new plastic pipe through the remainder of the cast iron pipe in order to reconnect the water supply and by the start of October, STW completed repair work to their damaged pipe.
As we enter October, we have produced a series of drawings, informed by our various investigations of structure, materials and voids illustrating the repair work required.
Results of our investigations are crucial in understanding what we need to do to restore the bridge back to a full strength and address any further deterioration. We are consulting closely with conservation officers to ensure the bridge is properly restored.
In order to make the bridge safe, the process is likely to involve injecting grout into the bridge to fill in the holes, repoint the masonry, and replace any missing bricks to return the structure to full strength.
We continue to work with Network Rail on access agreements to the railway and we are working together to get these repairs completed as quickly as possible.
The investigation reports also allow us to carry out detailed calculations of the load bearing of the bridge as it currently stands. This work is on-going and the results are expected by the end of next week (w/c Monday 8th October). Once the calculations are complete it may be possible to determine if the road can safely be re-opened in some way before the full bridge repairs are complete.
At present, a Road Closure Notice is in place until the end of November.
Cllr Matthew Holmes, Deputy Leader said:
“We appreciate that this situation has been incredibly frustrating for residents and businesses in the area but our priority has to be to ensure the bridge is repaired safely for the long term good of the city’s infrastructure, and to prevent a potential catastrophe.
“We thank everyone for their patience and we continue to do our best to get the road re-opened as soon as possible, given the constraints we face.”