We see it too often. A contractor sinks a foundation near Alkali Creek, hits sandstone with hidden fractures, and the sump pump runs nonstop after the first heavy rain. They skipped the field permeability test. In Billings, where the Rimrock sandstone meets alluvial clay, guessing the hydraulic conductivity is a gamble you don't want to take. Our lab runs Lefranc and Lugeon tests to give you real numbers before concrete hits the ground. We also pair these with grain size analysis when we need to cross-check the fines content from borehole cuttings. The combination tells you if that sandy silt layer will actually drain or just hold water against your wall. Getting the packer set right in a fractured zone isn't easy, but our crew has done it across Billings from the Heights to South Side without losing a hole.
A Lugeon value below 3 in Rimrock sandstone usually means you need a grout curtain. Above 10 and you are in full drainage territory.
