One of the most costly assumptions in Fort Worth construction is that a borehole log alone can predict how water moves through the ground. When contractors skip direct measurement and rely solely on grain-size correlations for the Eagle Ford Shale or alluvial deposits along the Trinity River, they end up with dewatering systems that either fail during the first heavy rain or are so oversized they drain the project budget. A field permeability test—whether a Lefranc in soil or a Lugeon in weathered rock—provides the in-situ hydraulic conductivity value that laboratory estimates cannot replicate. The local geology, with its alternating layers of stiff clay and fractured limestone, demands this data before designing retention systems or estimating inflow for deep excavations near the Cultural District. Without it, the margin for error is simply too wide.
In the layered shale and limestone of Fort Worth, a grain-size correlation can misrepresent hydraulic conductivity by an order of magnitude compared to a direct in-situ measurement.
Technical details of the service in Fort Worth
Risks and considerations in Fort Worth
A Lugeon test in Fort Worth requires a high-pressure pump capable of delivering up to 10 bars to overcome friction losses in the drill rods and to pressurize the packed-off interval. The double-packer assembly, typically inflated with nitrogen, seals the test section while water is injected in five or six pressure steps following Houlsby’s procedure. The technician watches the flow meter and pressure gauge simultaneously, noting any sudden increase in flow that signals hydrofracturing of the shale or the opening of a clay-filled joint. In the Lefranc configuration, a perforated casing section or an open borehole interval is used with a sensitive flow meter to detect the subtle head changes in low-permeability clays. In both cases, the equipment must be meticulously de-aired before starting because even a small air bubble in the line can compress under pressure and mimic a permeable zone, leading to a falsely high conductivity value that could compromise an entire slope stability analysis for a highway cut.
Our services
Field permeability testing in the Fort Worth area is conducted using methods consistent with the prevailing hydrogeological conditions. Our principal services encompass:
Lefranc Permeability Testing in Soil
Conducted in boreholes drilled through the alluvial and residual soils common along the Clear Fork and West Fork of the Trinity River. We use both constant-head and variable-head configurations, selecting the procedure based on the expected hydraulic conductivity range. Results are reported in cm/s and include temperature-corrected viscosity values when required by project specifications.
Lugeon Packer Testing in Rock
Applied to the fractured limestone and sandstone formations underlying the western part of the city. Each test stage is isolated with a pneumatic packer system and subjected to a stepped pressure cycle. The resulting Lugeon values are mapped against depth to identify the most conductive fracture zones, critical data for designing cut-off walls or grouting programs beneath major structures.
Quick answers
When is a Lugeon test recommended over a Lefranc test in Fort Worth?
A Lugeon test is the appropriate choice when the target stratum is fractured rock—most commonly the Walnut Formation limestone or the Paluxy Sandstone. The packer system isolates specific fracture sets, allowing the operator to measure conductivity under pressure steps. Lefranc tests are more suitable for the overlying residual clays and alluvial sands where a simple borehole infiltration method provides representative values without the need for packers.
What is the typical price range for a field permeability test in the Fort Worth area?
How many Lugeon pressure steps are run per test stage?
We follow the standard Houlsby procedure with five or six pressure steps per isolated stage, typically applying low-medium-high-medium-low pressure cycles. This pattern helps identify the onset of turbulent flow, fracture dilation, or hydrofracturing. Each step is held until a steady flow rate is achieved, and the entire sequence is recorded digitally for later analysis.