Repair work at a landslip site near Rothbury, Northumberland, is scheduled to begin in February 2015 - more than two years after the incident occured.
The landslip started on Boxing Day 2012, with conditions worsening over the following winter and spring. The B6344 road at Crag End has since been closed to all vehicles and pedestrians.
Following the geotechnical investigation and study of groundwater, a retaining wall along the side of the road was proposed. The wall, together with permanent deep draining, will provide long-term stability for the road.
The original budget for the work was £7.6M, with £4.9M provided through government funding. However, the difficult ground conditions and the further drainage to be undertaken will see Northumberland County Council invest an additional £1.5M for the project. To control groundwater during the impending construction work, eight boreholes, up to 55m deep, have been installed with 80 well points six metres deep.
It is anticipated that the contract for the construction work will be awarded within the next few weeks. The work is scheduled to be completed by October 2015.
Phase 1 ground investigation works by Dunelm Geotechnical and Environmental.comprised 15 cable percussive boreholes with rotary follow on using specialist “Geobore S” rotary techniques. Phase 2 works comprised 11 cable percussive boreholes with selected holes, also further advanced by rotary coring using Geobore S rotary techniques.
Inclinometers and electronic vibrating wire piezometers were installed in the boreholes and monitored regularly.
Access for the ground investigations was difficult due to the unstable ground conditions and the amount of drainage that was necessary on site. The extensive drainage works carried out will need to be further enhanced during the construction phase of the project.