Dallas sits on a complex geological seam where Blackland Prairie clays meet the weathered shale of the Eagle Ford formation. The city's rapid expansion northward through the 1980s pushed development onto these highly plastic soils, where water movement controls everything from basement waterproofing to pond integrity. A standard borehole log tells you soil type, but it cannot quantify how water actually flows through fractures, slickensides, or sandy interbeds beneath the root zone. That is where the in-situ field permeability test, specifically the Lefranc and Lugeon methods, becomes indispensable.
Our team runs these tests under ASTM D4630 and D4631 protocols, deploying the Lefranc method in granular soils above the water table and the Lugeon packer system in fractured rock at depth. For projects near the Trinity River corridor, we often pair field permeability profiling with grain-size analysis to correlate hydraulic conductivity with fines content, giving the design engineer a defensible basis for dewatering estimates and cutoff wall specifications.
In Dallas expansive clays, a lab perm test sees the soil — a Lefranc test sees the cracks that actually move water.
Methodology and scope
We isolate the test zone with bentonite seals and measure flow under steady-state conditions, correcting for hydrostatic pressure and casing geometry per the Hvorslev method. When the project involves dam abutments, retention ponds, or deep shafts penetrating the Woodbine sandstone, we switch to the Lugeon configuration with single or double packers. The result is a repeatable Lugeon value that the geotechnical engineer plugs directly into seepage and grouting analyses. Every test package includes digital flow logs, time-pressure curves, and QA/QC documentation aligned with USACE EM 1110-2-1901.
Site-specific factors
DFW International Airport sits at 607 feet above sea level, and the terrain drops roughly 200 feet into the Trinity River floodplain, creating hydraulic gradients that drive seepage through terrace deposits and weathered bedrock. Ignoring in-situ permeability data on a site with even a 15-foot cut can transform a routine excavation into a chronic dewatering failure, complete with slope instability and adjacent structure settlement. The 2018 Dallas Floodway Extension project underscored how quickly unanticipated groundwater flow derails schedules when permeability assumptions come from textbook tables rather than field measurement.
For critical infrastructure — levees, stormwater detention vaults, deep foundations near White Rock Creek — the Lefranc or Lugeon test is not an add-on. It is the parameter that governs drain spacing, pump sizing, and cutoff wall depth. A few thousand dollars allocated to field permeability characterization during the geotechnical investigation routinely saves tens of thousands in change orders once the excavator hits water.
Relevant standards
ASTM D4630 – Lefranc constant/falling head, ASTM D4631 – Lugeon pressure test in rock, USACE EM 1110-2-1901 – Seepage analysis & control
Related services
Borehole Lefranc Testing (Soil)
Constant-head and falling-head Lefranc tests in cased boreholes with bentonite isolation seals. We target SM, SC, and CL strata above the permanent water table, delivering k values for dewatering design and infiltration basin sizing.
Lugeon Packer Testing (Rock)
Single and double packer Lugeon tests in NQ/HQ core holes penetrating Eagle Ford shale, Austin Chalk, and Woodbine sandstone. We record pressure-step cycles per Houlsby interpretation, providing Lugeon units for grouting and seepage cutoff design.
Variable Head Permeability in Monitoring Wells
Slug and rising-head tests in 2-inch PVC monitoring wells installed in the Trinity alluvium. Data reduction via Bouwer-Rice or Hvorslev methods, suitable for environmental site assessments and groundwater modeling inputs.
Integrated Permeability & Soil Classification Package
Combined field permeability testing with laboratory grain-size distribution and Atterberg limits on the same borehole. This correlation package supports USCS classification and defensible permeability assignments for geotechnical baseline reports.
Typical parameters
Quick answers
What does in-situ field permeability testing cost for a typical Dallas project?
A single-borehole Lefranc or Lugeon test package, including mobilization within the Dallas-Fort Worth metroplex, equipment setup, packer isolation, flow measurement, and a signed engineering report, generally runs between US$720 and US$920 per test interval. Projects requiring multiple depths or double-packer setups fall toward the upper end. We provide a fixed-price proposal after reviewing the boring logs and target test depths.
When should I specify a Lugeon test instead of a Lefranc test?
The Lefranc method works well in soil and completely weathered rock where the borehole wall stands without casing support. Once you are into moderately fractured or competent rock — typical of the Eagle Ford formation below 15 feet in Dallas — the Lugeon test with a pneumatic packer becomes the correct tool. It isolates a specific test interval and measures water take under staged pressures, revealing fracture permeability that a simple Lefranc test cannot distinguish.
How long does a field permeability test take on site?
For a single Lefranc test in soil, expect 60 to 90 minutes of active testing after borehole preparation and seal placement. A Lugeon test with five pressure steps in rock typically requires 90 to 120 minutes per interval. We coordinate directly with the drilling crew to sequence the permeability test immediately after the test depth is reached, minimizing standby time and keeping the overall investigation schedule on track.
Which ASTM standard governs the Lefranc and Lugeon permeability tests?
The Lefranc constant- and falling-head test in soil follows ASTM D4630, while the Lugeon pressure test in rock is performed under ASTM D4631. Both standards define equipment requirements, test procedures, and calculation methods. Our field reports cite the specific revision year used and include all raw flow and pressure data for third-party review.