Compliance with the International Building Code (IBC) and ASCE 7 requires accurate subsurface hydraulic conductivity data before breaking ground in Sonoma County. In Santa Rosa, where alluvial deposits meet volcanic bedrock, guessing permeability is a costly risk. Our team executes in-situ Lefranc and Lugeon tests to deliver the precise data your geotechnical report needs. We don't rely on lab estimates alone; we measure how water actually moves through the specific strata under your site. A CPT test can map stratigraphy, but only a direct permeability measurement confirms flow rates critical for dewatering design. Our ISO 17025 accredited laboratory processes the readings, ensuring every value meets ASTM D6391 standards for defensible engineering decisions.
A Lugeon test in fractured bedrock tells you more about groundwater movement in ten minutes than a dozen lab permeability tests on intact samples.
Questions and answers
What's the difference between a Lugeon and a Lefranc test?
The Lugeon test is a packer test for fractured rock. It isolates a specific section of the borehole and subjects it to water pressure to measure rock mass permeability. The Lefranc test is for soils, typically installed below a casing, and measures the permeability of the soil matrix itself using a constant or falling head method. In Santa Rosa, we use Lugeon in the hillside bedrock and Lefranc in the valley floor alluvium.
How long does a field permeability test take on site?
A single Lefranc test in soil typically requires about 1 to 2 hours of field time once the borehole is advanced to the target depth. A Lugeon test in rock with a full five-stage pressure cycle usually takes 1.5 to 2.5 hours per test interval. The total duration depends on the number of test depths required by the project specifications.
What does a permeability test cost in Santa Rosa?
The cost for a single in-situ permeability test in Santa Rosa generally ranges from US$670 to US$1,010, depending on the depth of the test interval and whether it's a Lefranc or Lugeon method. This includes the mobilization of the drill rig, the testing equipment, and the engineering analysis report. A full-day testing program with multiple intervals will be priced based on the specific scope of work.
Why can't I just use lab permeability tests on core samples?
Lab tests on small intact samples miss the macro-features that control groundwater flow—fractures, fissures, and gravel lenses. A rock core might look solid but the rock mass could have open joints with high permeability. In granular soils, it's nearly impossible to collect an undisturbed sample that truly represents the in-situ density. The Lugeon and Lefranc tests measure the bulk permeability of the formation as it exists in place, which is far more representative for dewatering and drainage design.
