Windsor Drive Sinkhole, Hertford

KEY FACTS

Windsor Drive Sinkhole, Hertford

Following leaking drains, a ground collapse occurred below the rear corner of the house breaking service connections, causing major crack damage and subsidence of the house wall, the foundations, patio and nearby garden shed.

PBA was engaged to determine the cause of ground movement and damage. The subsidence occurred in an area where glacial sands & gravels overlay chalk and many local sinkholes were recorded in the PBA Natural Cavities database.

A series of dynamic probes and boreholes revealed a deep solution pipe underlying the surface sinkhole that extended to around 30m depth below ground level. The disturbed ground within the solution pipe was loose with further possible upward migrating voids.

Ground stabilisation was recommended as the optimum remedial solution to mitigate the problem. Considerable difficulties were overcome to gain access to the rear of the property via local council owned land and a neighbour’s garden. A working platform was created and compaction grouting was carried out to reinstate the ground support to the house. New foundations were constructed below the corner of the house and the corner re-built above to bring matters to a successful conclusion.