The soil conditions between Milwaukee's East Side and the Menomonee Valley are a study in contrasts. Up on the bluff, dense glacial till and Silurian dolomite bedrock control infiltration rates, while the valley's 150-foot-thick sequence of lacustrine clays, silts, and buried river channels can halt groundwater flow almost entirely. A generic permeability estimate from a textbook won't work here. When a contractor near the harbor needs to design a deep sump for a new mid-rise, or an engineer in Walker's Point must predict settlement under a mat foundation, the field permeability test (Lefranc/Lugeon) becomes the central piece of the geotechnical puzzle. We run these in-situ tests across the county, measuring hydraulic conductivity directly within the formation—whether in a soft silty clay or a fractured dolomite—to give you the numbers that pump manufacturers and structural designers actually need.
A single Lefranc test in a silty till can reveal a conductivity value that renders a textbook-based dewatering estimate off by an order of magnitude.
Local geotechnical context
Milwaukee sits at the collision point of continental air masses and Lake Michigan's moisture engine, a geographic reality that makes groundwater management a year-round challenge. Spring snowmelt saturates the near-surface fill, while summer thunderstorms can cause rapid rises in the shallow aquifer perched above the dolomite. A dewatering system designed without accurate in-situ K-values from a field permeability test (Lefranc/Lugeon) either runs pumps 24/7 burning diesel and cash, or more dangerously, it fails to lower the water table enough to keep the excavation bottom stable. We've seen projects in the Kinnickinnic River corridor where the difference between an assumed permeability and a measured one meant the contractor needed 30% more wellpoints. In fractured rock slopes along the lakefront, a Lugeon test reveals the real risk of water pressure build-up behind a retaining wall—a scenario that can lead to a sudden failure during a winter freeze-thaw cycle. Collecting that data early prevents a budget-busting redesign later.
Relevant standards
ASTM D6391-11: Lefranc field permeability testing, IBC Section 1803: Geotechnical investigations, ASCE 7-22: Minimum design loads (drainage and lateral earth pressure), USBR Design Standard No. 13: Lugeon testing in rock, ASTM D653: Standard terminology for soil, rock, and contained fluids
Quick answers
How much does a field permeability test (Lefranc/Lugeon) cost in Milwaukee?
For a typical Lefranc test in overburden soil, budget between US$590 and US$1,130 per test zone, which includes drill rig time, packer setup, and data analysis. A Lugeon test in bedrock runs at the higher end of that range due to the multi-pressure stage procedure and longer equipment setup. The total project cost depends on the number of test intervals, access constraints for the drill rig, and whether we need to install monitoring wells first.
How long does a Lefranc test take in the field?
A single Lefranc test in a stable borehole typically takes between 45 and 90 minutes. This includes isolating the test interval with a packer, saturating the formation, and running at least two head levels to confirm data consistency. If the soil is very tight—like many of the lacustrine clays in the Menomonee Valley—the falling head phase can stretch the test beyond two hours to capture a meaningful response. We plan our drilling schedule to allow for this variability.
What is the difference between a Lefranc test and a Lugeon test?
The core difference is the material being tested and the pressure application. A Lefranc test is a low-pressure method used in soil, weathered rock, and very soft bedrock, measuring how water naturally flows in or out of an isolated borehole section. A Lugeon test is specifically for competent, fractured rock like the dolomite under Milwaukee. It uses a packer system and a pump to inject water at multiple pressure stages, revealing how fractures open or close under pressure. The Lugeon test tells you if the rock needs grouting; the Lefranc test tells you how fast you'll need to pump to keep an excavation dry.
Can you run a permeability test in the same borehole as an SPT?
We generally prefer a separate, dedicated borehole for permeability testing to avoid smearing the borehole wall with drilling mud or collapsing the test zone. However, if the soil conditions are stable and the test interval is in a uniform clay or till, we can sometimes advance the hole with hollow-stem augers, perform the SPT at the desired depth, and then set a packer in the auger stem to run a Lefranc test before moving deeper. This saves on mobilization cost but requires careful planning to ensure the SPT disturbance doesn't bias the permeability data.
