Drillers in the Madison area know the drill: you hit dense glacial till in Verona one day and heavily jointed Eau Claire sandstone the next. The real challenge is quantifying how water moves through either. On a recent project near the Yahara River, standard lab perm tests failed to capture the secondary porosity we saw in the core samples. That is why we run in-situ permeability tests. A test pit might expose the top five meters, but a properly executed Lefranc or Lugeon test reveals hydraulic conductivity across the entire depth of interest. When dewatering for a deep excavation downtown or assessing bedrock grout take, you need field data, not textbook estimates.
A single Lugeon value of 3 in Eau Claire sandstone can mean tight fractures or wide joints filled with silt—only the pressure curve tells the difference.
