Efforts to drill three boreholes near Leeson Road are expected to conclude this week, according to the Isle of Wight council. The deepest borehole will reach a depth of 130 metres, with two already completed.
The boreholes are part of ongoing monitoring to assess ground stability and manage landslip risks in the area. This data is critical for the safe re-opening of Leeson Road, which has been closed due to concerns about ground movement, following the catastrophic landslide in December 2023.
Ground movement monitoring
The first borehole, completed at 115 metres, is equipped with inclinometers that measure ground movement. This allows for continuous monitoring of shifts in the terrain.
The second borehole, drilled to 130 metres, also houses an inclinometer. This depth enables the collection of data on groundwater conditions across the wider area, which influences landslip risks.
Challenges with the third borehole
Drilling the third borehole has been more complex. At a depth of approximately 125 metres, the casing became stuck in the greensand layer. Repeated attempts to retrieve it were unsuccessful.
As a result, an alternative borehole is being drilled nearby. This will house piezometer tips designed to record underground water pressure, a significant factor in ground movement. The new borehole is planned to reach 100 metres and is expected to be completed this week.
The original borehole will be backfilled, as the stuck casing prevents its use for monitoring purposes.
Next steps and road reopening plans
Once the third borehole is finished, monitoring equipment will be installed. Combined with existing equipment, the new data will support an early warning system to manage landslip risks effectively.
The council say they are committed to re-opening Leeson Road as soon as it is deemed safe, with an agreement in place for ongoing monitoring and risk management.
Isle of Wight council leader, Phil Jordan, last week told OnTheWight that the target date for a “full road opening” of Leeson Road is the end of November 2024.
Find out more
Further information about the Undercliff landslide complex can be found on the IWC website.
