Work to sink 3 boreholes on Ventnor’s Leeson Road, the deepest of which reaches a depth of 130m, is expected to finish this week – but there is still no word on when the key A-road will re-open.
2 of the boreholes are already completed. The first of these is 115m deep and houses an array of inclinometers which records ground movement.
The second is to a depth of 130m and also houses an inclinometer. Boring to this depth allows for gathering data about groundwater conditions across the wider area – over and above what is needed for the safe re-opening of Leeson Road.
The third borehole has proved more challenging. After casing became stuck in the greensand layer (approximately 125m underground) and numerous attempts to retrieve it failed, it was necessary to drill an alternative borehole nearby to house the agreed monitoring equipment — several piezometer tips which record underground water pressure. Underground water is a major factor in ground movement.
The aim is to sink this borehole to 100m. It is anticipated this depth will be reached this week after which the monitoring equipment can be installed. The original borehole will be backfilled because the casing stuck within it prevents any meaningful monitoring.
Data recovered from the equipment installed in these boreholes – added to that already being retrieved from new and existing equipment – will give all the information needed to manage an early warning process that will allow the road to be re-opened and operated safely in parallel to the landslip risk, but the local authority has not said when the road will re-open as normal.
A spokesperson has said:
“Island Roads and the Isle of Wight Council can assure residents that our intention remains to re-open the road as soon as we are satisfied it is safe to do so and we have agreement in place to ensure effective ongoing management. We will continue to keep the community informed”.
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