Calgary sits on a thick sequence of glacial till and glaciolacustrine deposits, with the water table often perched at shallow depths in the river valleys. The till here is a dense, heterogeneous mix of clay, silt, sand, and gravel that can vary laterally within meters — a challenge that makes the Standard Penetration Test (SPT) indispensable for characterizing subsurface strength. In our experience, N-values from SPT correlate directly with the bearing resistance of these tills, helping engineers decide whether a shallow spread footing or a deeper pile system is needed. Before mobilizing a drill rig, a preliminary calicatas exploratorias can help map the vertical stratigraphy and identify boulder layers that might stop SPT advancement. The test itself follows CSA A23.2-9A / CSA A23.2-9A / CSA A23.2-9A / CSA A23.2-9A / CSA A23.2-9A / ASTM D1586, with the split-spoon sampler driven 300 mm and blows counted per 150 mm increment. For Calgary projects, we typically record N-values between 20 and 50 blows per 300 mm in the competent till, though softer lacustrine clays may yield lower counts. This local baseline is critical for foundation design under the Alberta Building Code.
N-values between 20 and 50 in Calgary’s glacial till provide reliable bearing capacity estimates, but interbedded silt lenses can shift seismic site class from C to D.