The results will help shape the design of the cliff stabilisation and coast protection scheme, which we are planning.
The investigation work, expected to last four weeks and paid for with an Environment Agency grant, will see a series of boreholes drilled through the cliff up to a depth of 40m (131ft). Three boreholes will also be drilled through the promenade in front of the Spa. These will be up to 20m deep to determine the depth of the bedrock.
Additional monitoring equipment to complement existing equipment will be installed in the new boreholes to measure groundwater levels and movements within the cliff and will be monitored for an initial period of six months to provide data for the design of the coast protection scheme. Samples will be taken from the boreholes during the ground investigation, which will include soil samples and rock cores. Those samples will be tested in specialist laboratories to provide information on the composition and strength of the materials in the ground.
We apologise for any disruption, which may be caused as a result of the temporary closure of some footpaths in the South Cliff Gardens but the measures are necessary to allow the drilling work to be carried out without putting the safety of the public at risk. Information about footpath closures will be posted at the Spa and on Esplanade for the duration of the work and diversions will also be signposted.
Cllr Mike Cockerill, Cabinet Member for Harbours, Assets, Coast and Flood Protection, said:
“Although there is some existing information available as a result of previous works and ongoing monitoring, more information is needed about ground conditions including geology, groundwater and depths of ground movement to help determine the design of the structures that will make up the final coast protection scheme.
“It’s critical we come up with a combined solution to ensure the long term stability of both the sea wall and the cliffs, as, contrary to some opinions expressed in the media, the two elements are very much connected.”
The current condition of the sea wall is deteriorating and while a make-do-and-mend approach has worked to a degree until now, there are significant signs of undercutting of the toe, cracking and loss of joint material, voiding behind the sea wall and displacement of masonry blocks, all affecting the stability of the wall.
If the sea wall fails and erosion occurs, the cliff would become even more unstable and the likelihood of a major landslide increases greatly. If a major landslide does happen, it is likely it will overrun the sea wall and destroy it completely – this scenario was played out during the Holbeck Hall landslip in 1993. Collapse of the sea wall would allow erosion to start either side of the landslip and the cliff could unravel either side leading to further landslides.