Field Permeability Testing (Lefranc/Lugeon) in Peoria, Illinois

Too many foundation dewatering plans in Peoria fail because the design relies on lab permeability from disturbed samples. Pulling a Shelby tube and testing it back at the office doesn't capture fissures in the till or the true secondary permeability of the loess mantle. We see it often near the Illinois River bluffs where groundwater moves through preferential pathways that a textbook grain-size correlation completely misses. This is where the Lefranc test and Lugeon test earn their keep. Running an in-situ permeability measurement directly in the borehole gives you the actual mass hydraulic conductivity your pumps will face. Our field crew operates across the Tri-County area, from downtown Peoria foundations to outlying Tazewell County subdivisions, using AASHTO-compliant variable-head methods that feed directly into your dewatering and stability models.

Lab permeability on a remolded sample is a guess. A Lefranc test in the borehole is a measurement of how the ground actually transmits water.

Our approach and scope

ASTM D4631 and the USBR Earth Manual guide the Lefranc method for soils, but in Peoria the real value is adapting the test interval to match the depositional sequence. A constant-head test in the sandier outwash layers above the Glasford Formation tells a completely different story than a falling-head test in the underlying diamicton. When the borehole encounters bedrock—typically Pennsylvanian shale or limestone beneath the Illinois River valley—we switch to the Lugeon protocol, injecting water under pressure in discrete five-foot stages. This dual approach matters for projects like the combined sewer overflow tunnels, where contractors need reliable permeability values to estimate grout takes. For deeper investigations in weathered shale, combining the packer test with a CPT profile clarifies whether high water takes are fracture-controlled or just poor rock quality.

Local geotechnical context

A common pitfall we observe in Peoria dewatering plans is assuming the Illinois River alluvium is homogeneous. In reality, the Henry Formation outwash often contains pockets of open-work gravel directly adjacent to dense, low-permeability till. Running a Lefranc test at only one depth interval—or worse, skipping it entirely in favor of a lab constant-head test—leads to pump specs that are either grossly oversized or dangerously undersized. We've consulted on excavations near the McClugage Bridge where water inflow from a thin gravel seam was an order of magnitude higher than the design predicted. For dam safety reviews and slope stability analyses along the riverfront, the Lugeon test provides the hard numbers on bedrock fracture connectivity that a simple RQD log can't match.

Technical parameters

Parameter	Typical value
Test Methods	Variable-head (falling/rising) and constant-head per ASTM D4631; Lugeon packer test per USBR 6515
Applicable Soils	Glacial till, loess, alluvial sands, weathered shale, fractured limestone
Borehole Diameter	NQ to 6-inch rotary; hollow-stem auger for Lefranc in caving soils
Test Interval	Standard 5-ft packer spacing for Lugeon; custom soil zones for Lefranc
Reporting	k-value (cm/sec), transmissivity, Lugeon units, QA/QC plots of flow vs. pressure
Packer Type	Single pneumatic packer for shallow rock; double packer for discrete fracture testing
Correlation	In-situ k values cross-checked with grain-size Hazen estimates when applicable

Related services

Lefranc Variable-Head Testing

Constant or falling-head tests run inside hollow-stem augers through the Peoria silt and Glasford till. We isolate specific strata to give you a layered permeability profile for dewatering system design.

Lugeon Packer Testing in Rock

High-pressure water injection in NQ or NX boreholes to quantify fracture flow in the Pennsylvanian bedrock beneath Peoria. Standard five-foot test intervals, with step-pressure testing to assess hydraulic fracturing risk.

Dewatering Feasibility & Pump Test Support

Integration of Lefranc/Lugeon data with monitoring wells to size wellpoints, deep wells, or eductor systems for excavations near the Illinois River or in the downtown Peoria area.

Quick answers

What's the ballpark cost for a Lefranc or Lugeon test in Peoria?

For a typical field permeability testing program in central Illinois, budget between US$690 and US$920 per test interval, assuming the borehole is already being drilled. The final cost depends on depth, number of stages, and whether we're setting a single or double packer. Mobilization within the Peoria metro area is included in our standard day rate.

When should I choose a Lugeon test over a Lefranc test?

Lefranc is for soils—loess, till, sand, gravel—where the borehole stays open or is cased with a slotted screen. Lugeon is strictly for rock. If your Peoria project hits limestone or shale at 40 to 60 feet, you'll need a Lugeon packer test to measure how connected the fractures are. We often run both on the same hole: Lefranc in the overburden, Lugeon in bedrock.

How long does a field permeability test take on site?

A single Lefranc falling-head test in granular soil may stabilize in 15 to 30 minutes. Low-permeability till can take an hour or more. A standard five-stage Lugeon test in rock typically requires two to three hours of rig time, including packer inflation and step-pressure runs. We always coordinate with your driller to minimize standby time.