Field Permeability Testing (Lefranc/Lugeon) in Arlington, TX

Arlington sits on a complex transition zone where the Eagle Ford Shale meets younger alluvial deposits from the Trinity River tributaries. The Johnson Creek floodplain cuts through north Arlington, creating pockets of sandy loam that drain fast, while the weathered shale south of I-20 holds water differently. This variability matters when you are designing retention ponds for the Entertainment District or dewatering a deep excavation near AT&T Stadium. A standard borehole log gives you material description, but it does not tell you how fast water actually moves through the formation. That is where a field permeability test becomes essential. We run both Lefranc tests in soil and Lugeon tests in fractured rock following ASTM D4630 and D4631 protocols. The data feeds directly into seepage analyses, cutoff wall design, and pump sizing for construction dewatering across Tarrant County's variable lithology.

A Lugeon value above 10 Lu in Arlington shale indicates fracture flow that standard borehole logging will miss entirely.

Methodology and scope

The hydraulic contrast between east Arlington's sandy Johnson Creek terraces and the shale-dominated uplands west of Cooper Street is striking. In the eastern neighborhoods, we often measure permeability coefficients in the 10^-4 to 10^-3 cm/s range using the Lefranc constant-head method in test pit excavations or boreholes. Those sands drain efficiently and dewatering can be straightforward if the aquifer is not confined by an underlying clay lens. Move west into the Cretaceous shale, and the picture changes. Intact Eagle Ford has matrix permeability below 10^-7 cm/s, but fractures and bedding planes can transmit significant flow. A Lugeon test with a single packer isolates discrete intervals and quantifies that secondary permeability. We have seen Lugeon values jump from 2 to 25 Lu within a 10-foot vertical section just because the borehole intersected a open joint set. Supplementing these tests with grain size analysis on recovered samples helps correlate hydraulic conductivity with gradation, and when the project requires rock mass characterization for slope stability, a seismic refraction survey can map weathered versus competent rock horizons before planning the permeability investigation.

Local geotechnical context

Summers in Arlington bring intense thunderstorms that can drop three inches of rain in six hours on saturated clay soils. A detention basin designed without site-specific permeability data risks overflowing during a 100-year storm event because the designer assumed a conservative infiltration rate from a textbook. We have seen the opposite problem too: an excavation support system specified with excessive well points because the contractor overestimated the in-situ permeability of a fractured shale unit. The Lugeon test provides a direct measurement of rock mass hydraulic conductivity that accounts for fracture aperture, spacing, and connectivity — parameters that no lab test on an intact core sample can reproduce. In dam foundation assessments along the West Fork of the Trinity River, low Lugeon values below 3 Lu often indicate that a grout curtain can achieve the target reduction, while values above 15 Lu may require closer primary-secondary-tertiary hole spacing and a staged grouting program to seal the fracture network effectively.

Typical values

Parameter	Typical value
Test method (soil)	Lefranc — constant or falling head per ASTM D4630
Test method (rock)	Lugeon — single/double packer per ASTM D4631
Typical test interval	3 to 5 ft in soil; 10 to 20 ft in rock
Measurement range	10^-7 to 10^-1 cm/s (Lefranc); 0.1 to 100+ Lu (Lugeon)
Packer type	Pneumatic single or double packer, 2-6 inch diameter
Pressure stages	5-stage cycle (Lugeon): low-medium-high-medium-low
Applicable standards	ASTM D4630, D4631, USBR 7300-89, Hvorslev method
Reporting output	k (cm/s) or Lugeon units; flow vs. pressure plots

Complementary services

Borehole Lefranc Testing

Constant or falling head tests in soil borings at specified depths. Used for dewatering design, infiltration rate verification, and seepage analysis in alluvial and residual soil profiles.

Single-Packer Lugeon Testing

Isolates discrete 10-20 ft intervals in rock coreholes. Five-stage pressure cycle identifies fracture flow regime: laminar, turbulent, dilation, or wash-out. Standard for dam foundation and grouting assessments.

Test Pit Infiltration Testing

Open-pit falling head tests in shallow excavations per ASTM D3385 for stormwater infiltration BMP design. Direct measurement in the unsaturated zone where borehole methods are less reliable.

Multi-Level Piezometer Installations

Post-test monitoring with nested or multi-port piezometers to verify hydraulic gradients and provide long-term pore pressure data for slope stability and excavation monitoring programs.

Relevant standards

ASTM D4630 — Standard Test Method for Determining Transmissivity and Storage Coefficient of Low-Permeability Rocks by In Situ Measurements Using the Constant Head Injection Test, ASTM D4631 — Standard Test Method for Determining Transmissivity and Storativity of Low Permeability Rocks by In Situ Measurements Using Pressure Pulse Technique, USBR 7300-89 — Procedure for Performing and Reporting Lugeon Tests in Rock, Hvorslev (1951) — Time Lag and Soil Permeability in Ground-Water Observations

Quick answers

How much does a field permeability test cost in Arlington, TX?

A single Lefranc or Lugeon test in a standard borehole typically runs between US$700 and US$960, depending on depth, access conditions, and whether a packer setup is required. Mobilization, drilling subcontractor costs, and multi-level testing programs are quoted separately based on the scope of work.

When should I specify a Lugeon test instead of a Lefranc test?

Use the Lefranc method in soil or heavily weathered rock where the borehole wall is stable enough to maintain an open test cavity. Specify a Lugeon test with packers when you need to measure hydraulic conductivity in competent but fractured rock, especially where fracture flow dominates and you want to isolate specific depth intervals to guide grouting or cutoff wall design.

How many pressure stages are required for a valid Lugeon test?

The standard procedure follows a five-stage cycle: low, medium, high, medium, low pressure. This pattern reveals whether the fracture system dilates or erodes under higher pressures. The ratio between the first and last low-pressure stages indicates if the test has altered the flow path, which is critical for interpreting results correctly.