Work to reopen the Beaminster Tunnel has been delayed and will now not meet its original opening deadline of May.
The complex project involves negotiations with four different landowners as well as very specialist testing and design work which must be completed before the main works can begin.
Following a considerable increase in the number of landslips across the country, due to the high levels of rainfall experienced during 2012, geotechnical engineers have been in high demand.
The companies contracted by Dorset County Council to test the tunnel site and design the stabilisation works have both completed their work later than originally expected.
Negotiation with landowners is continuing while the results of the test nails on the north side of the tunnel have allowed the geotechnical engineers to refine their design.
This will be beneficial for the works and the land negotiation.
Although considerable advanced preparation works continue to be carried out, it has not yet been possible to start the soil nailing as programmed and it is now likely that the road will not be opened at the end of May.
Councillor Peter Finney, cabinet member for highways and transportation at Dorset County Council, said, “We know this is devastating news for the community, and it is certainly not what we had foreseen happening.
“The design process is complex and does take time. It is extremely important that we get it right. We are doing as much other work on site as we can – including improving the drainage – and we will re-jig parts of the programme where possible to keep the work moving.
“We’re getting the site prepared as far as possible given the current constraints so that when we have the green light we can get straight on with the main construction work.”
Councillor Rebecca Knox, Dorset County Council division member for Beaminster, said, “Residents, businesses and neighbouring parishes have been majorly inconvenienced due to the tunnel closure, and any delay is a massive blow.
“While the closure is in place, I am stressing the importance of getting other matters addressed, such as road surfacing, drainage issues, intrusive weeds in the hedgerows, road signs and other matters that the communities in the area have been raising.
“The delay is very disappointing for all of us and I hope the highways project team will be able to get on with all aspects of the work as each matter is resolved to get the road reopened as soon as possible.”
Last month, test nails confirmed that soil-nailing will work to stabilise the slopes.
About a thousand nails will be driven into the ground and pin a material over the slopes to hold the land in place.
The masonry headwalls above the tunnel and the wing walls on the approach to the tunnel will be strengthened and new drainage will be installed to redirect rainwater and drain the slopes.
The £2.1m project is being funded by Dorset County Council.