The soil debris was removed from the hole using a tracked excavator and supervised by ASL. A concrete slab was encountered at the base of the hole which was lifted to enable inspection of the ground beneath to check for loose ground or voids. The ground beneath the slab was initially soft and wet although further excavation revealed competent natural clay materials at a depth of approximately 3m. All loose and soft materials were trimmed from the sides of the excavation and removed from the hole.
It is considered that the purpose of the slab may have been the base for a tank or an underground shelter which had been removed but not backfilled.
As there was no evidence of any Made Ground, soft or loose materials or voiding in either the base or sides of the excavation the excavation was backfilled with concrete. On completion of backfilling the hole has been suitably reinstated and did not present any further risks to the site.
ASL, acting as the Geotechnical Consultant, supervised the backfilling and provided a report confirming that the hole had had been suitability backfilled and present no further risks to the users of the care home.