More than one contractor in Dublin has pulled out muck from a shallow trench, assumed it was competent boulder clay, and poured the strip footing without a second thought. The problem: Dublin’s glacial till hides lenses of soft silty clay and pockets of running sand that don’t show up in a borehole log unless you’re looking right at them. An exploratory test pit opens a window straight into the ground profile—no extrapolation, no disturbed cuttings, no guessing. We excavate to 4.5 m depth where access allows, log the strata per BS 5930:2015, and sample at intervals that catch those thin interbeds. For deeper refusal verification the team often pairs the pit with SPT drilling where the till stiffens, and in loose backfill zones we run sand cone density tests to confirm compaction before the concrete goes in. In a city where site histories range from medieval basements to 1990s infill, skipping direct observation is a gamble you don’t want to take.
A test pit doesn’t just expose soil—it catches the thin interbeds, seepage zones, and backfill surprises that boreholes routinely miss.
