Too many St. Louis projects still rely on lab permeability from disturbed samples—and then wonder why dewatering estimates miss by 40 percent. Limestone joints, weathered shale seams, and Mississippi River alluvium don't reveal their true hydraulic behavior until you test them in place. We run field permeability tests across the region using Lefranc for soil and Lugeon for fractured rock. The difference is immediate: you get actual hydraulic conductivity at depth, not a number from a remolded specimen. For jobs near the riverfront or along the I-64 corridor, that data drives pump sizing, cutoff wall design, and grouting decisions. Before finalizing the foundation plan, an SPT drilling program often flags the zones that need permeability testing—saving time over drilling blind.
A single Lugeon test in fractured St. Louis limestone gives more actionable data than a hundred lab perm tests on core samples.
Process and scope
Local ground factors
A double pneumatic packer is the heart of a Lugeon test. We lower it to depth on drill rods, inflate the seals with nitrogen, and inject water through the test interval between them. If the packer doesn't seat properly in a rough limestone borehole—common in St. Louis karst—water bypasses the seal and the test is worthless. We use reinforced gland packers rated to 1,000 psi with extra extrusion gap control for exactly this reason. The Lefranc setup is simpler but just as sensitive. A slotted PVC screen surrounded by clean filter sand must be placed at the exact test depth. If the sand bridge collapses or the bentonite seal above it leaks, the head measurement is wrong. Our technicians log every step: packer inflation pressure, flow rate at each stage, water temperature, and recovery curve. On a recent MetroLink extension project, a faulty seal at 45 feet produced an artificially high permeability—caught during the test and corrected before the design team ever saw the report. That's the standard we hold on every St. Louis site.
Reference standards
ASTM D6391-11: Standard Test Method for Field Measurement of Hydraulic Conductivity Using Borehole Infiltration, USBR 6510: Permeability Tests in Individual Drill Holes, ASTM D5092: Design and Installation of Groundwater Monitoring Wells
Associated technical services
Lefranc Variable-Head Tests
Falling or rising head permeability in soil. We install the screen, develop it, and run multiple cycles until the stabilized k-value repeats within 10 percent. Standard for dewatering design.
Lugeon Packer Tests in Rock
Five-stage pressure test in fractured limestone, dolomite, or sandstone. Each pressure step runs 10 minutes. Flow vs. pressure curves reveal fracture dilation, erosion, or laminar flow behavior.
Open-Hole Injection Tests
Quick permeability screening in competent bedrock where a packer isn't required. Used for preliminary site assessments, grout take estimation, and landfill liner studies.
Typical parameters
Questions and answers
What does a field permeability test cost in St. Louis?
A single Lefranc or Lugeon test typically runs between US$620 and US$1,120, depending on depth and number of pressure stages. This includes mobilization, technician time, equipment, and the signed report. Multiple tests on the same borehole reduce the per-test cost since setup is already done.
How long does a Lugeon test take on site?
Plan about 90 minutes per test interval. That covers packer inflation, five pressure stages at 10 minutes each, deflation, and moving to the next depth. If the rock is highly fractured and takes a lot of water, we may extend stages to reach steady flow. Setup and breakdown add another hour at the start and end of the day.
Do I need both Lefranc and Lugeon tests on the same project?
Often yes, if the site has both soil overburden and bedrock. A typical St. Louis profile is 20 to 40 feet of alluvium over limestone. We run Lefranc in the soil layer and Lugeon in the rock below. That gives the dewatering contractor a complete hydraulic profile instead of guessing at the interface. More info.