Field Permeability Testing (Lefranc/Lugeon) in McKinney Texas

The Lefranc packer system goes down the borehole first, isolating the test zone with pneumatic seals. In McKinney, our crews often deploy this equipment right behind the truck-mounted drill rigs on sites east toward Lake Lavon, where the soil transitions from stiff clay into weathered Austin Chalk. The test itself is straightforward: we fill the standpipe, record the water drop over time, and repeat at several stages to profile the permeability across the layer boundaries. The Lugeon variant applies when the borehole hits fractured shale or limestone bedrock. Here we pressurize the interval and measure water take in Lugeon units. Both methods answer the same practical question for the design team: how fast does water move through the ground at this specific spot? In a region where shrink-swell clays dominate, the atterberg limits help us interpret whether the measured permeability will shift dramatically as the soil wets and dries.

A single Lugeon test in fractured McKinney shale tells you more about water inflow than a dozen lab permeameter runs on intact core.

Methodology and scope

North Texas weather swings hard. A dry summer bakes McKinney's blackland prairie clay until it cracks wide open; a wet spring turns those same fissures into preferential flow paths. That contrast is exactly why we calibrate field permeability tests to in-situ moisture conditions rather than relying on lab remolded samples alone. The test interval is typically one to three feet long. We run falling-head or constant-head setups depending on the expected hydraulic conductivity. In silty sands near the East Fork of the Trinity River, a constant-head test often gives cleaner data. When the formation is tighter—say, the Eagle Ford shale outcrops west of town—we switch to a pressure transducer and log the decay curve at sub-millimeter resolution. The resulting permeability coefficient feeds directly into dewatering design, retention pond sizing, and basement waterproofing decisions. For sites where the soil profile includes granular lenses, a companion grain-size analysis helps confirm whether the permeability value matches the expected drainage behavior of that material.

Field Permeability Testing (Lefranc/Lugeon) in McKinney Texas

Local considerations

McKinney's growth arc tells a clear story: farmland turned subdivision in under a decade. That rapid build-out means many retention ponds and basement slabs now sit on fill soils whose permeability was never measured in the field. The hidden risk is perched groundwater. A thin sand lens buried under compacted clay can trap runoff and create a localized water table that nobody planned for. We have pulled packers out of boreholes in Stonebridge Ranch and watched water rise two feet in ten minutes from a seam that the grading plans called impervious. The cost of skipping a field permeability test here shows up later as wet basements, failed retaining wall drains, or ponds that never hold water. The retaining-walls design in this area depends heavily on knowing whether the backfill will drain or retain pore pressure through a wet season.

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Applicable standards

ASTM D6391-11 (Lefranc), Houlsby method for Lugeon testing, USBR Earth Manual Part 2, ASTM D2487 (soil classification context)

Associated technical services

Lefranc falling-head testing

Variable-head tests in soil boreholes, logged at multiple depths to build a permeability profile for dewatering and infiltration analysis.

Lugeon pressure testing in rock

Packer-isolated intervals in fractured shale and limestone, with pressure stages following the Houlsby method for foundation grouting decisions.

Constant-head permeability in granular soils

Steady-state injection tests where the formation is too permeable for a falling-head setup, common in sandy lenses near the Trinity River.

Permeability test interpretation and reporting

Reduction of field data to hydraulic conductivity values, Lugeon unit plots, and geotechnical recommendations for drainage, cutoff walls, or dewatering systems.

Typical parameters

Parameter	Typical value
Test standard	ASTM D6391 for Lefranc; Houlsby method for Lugeon
Test interval length	0.3 to 1.0 m (1 to 3 ft) typical
Measurement method	Falling head, constant head, or pressure transducer
Applicable soil/rock types	Silts, clays, weathered shale, fractured limestone
Hydraulic conductivity range	Approximately 1×10⁻⁷ to 1×10⁻² cm/s
Lugeon value interpretation	1 Lugeon ≈ 1.3×10⁻⁵ cm/s; <1 very tight, >25 highly permeable
Borehole diameter	NX or HQ typical for packer seating
Reporting output	Permeability vs. depth profile, summary table, design recommendations

Frequently asked questions

What is the difference between a Lefranc test and a Lugeon test?

Lefranc tests are run in soil, typically using a falling-head or constant-head setup with a slotted pipe or open borehole section. Lugeon tests are run in rock, using a pneumatic packer to isolate the interval and injecting water under pressure in stages. In McKinney we use Lefranc in the clay and silt overburden, and switch to Lugeon when the borehole enters the weathered shale or limestone bedrock.

How long does a field permeability test take on site?

A single test interval usually takes 30 to 60 minutes once the borehole is drilled and the packer is set. A full profile with three to five test depths across a 40-foot borehole can be completed in one day. Saturated clay zones sometimes need longer stabilization time, so we let the data dictate the pace rather than the clock.

What does a Lefranc or Lugeon test cost in McKinney?

The field permeability test program typically ranges from US$640 to US$1,140 depending on the number of test intervals, depth of the borehole, and whether we are testing in soil, rock, or both. This includes mobilization to the McKinney site, the packer assembly, data acquisition, and the engineering report with permeability values and design notes.