The hydrogeologic contrast between a vineyard site off San Pasqual Valley Road and a hillside parcel in the Harmony Grove area can be stark, even though both sit within Escondido's city limits. One sits on deep alluvial deposits from the San Dieguito River basin, while the other is anchored in decomposed tonalite and fractured granitic bedrock typical of the Peninsular Ranges. When we run field permeability tests in these settings, the Lugeon method often takes center stage in the rock, and the Lefranc test becomes the workhorse in the overlying soils. Understanding which protocol fits the subsurface conditions is what turns a simple infiltration feasibility study into a defensible design parameter for detention basins, retaining wall drains, or deep excavation dewatering systems.
A single Lugeon value without a step-test curve tells you almost nothing about fracture flow regime—laminar, turbulent, dilation, or washout.
