Houston sits on a thick sequence of alluvial and fluvial deposits — sands, silts, and clays that vary dramatically over short distances. In our daily work, we see that a standard soil classification isn't enough when the water table sits just a few feet below grade. That is where a field permeability test becomes indispensable. We run the Lefranc method in shallow, unsaturated zones and switch to the Lugeon technique in bedrock or claystone layers where joint flow dominates. Both approaches give us direct, in-situ hydraulic conductivity values that lab tests on disturbed samples simply cannot match. Before planning a large excavation or a deep foundation system, we often pair this test with a study of expansive soils to evaluate how moisture changes could affect the building pad, and we also check infiltration rates for stormwater management design.
A single field permeability test can save weeks of dewatering delays and thousands in unexpected groundwater control costs.
Methodology and scope
Houston grew fast after the 1900 Galveston hurricane, and the city’s drainage network has been playing catch-up ever since. The flat coastal plain means water moves slowly, so knowing exactly how fast the ground can transmit water is critical for everything from detention ponds to highway underdrains. The Lefranc test works well in the sandy layers that dominate the Beaumont Formation, while the Lugeon test is better suited for the stiff clay and cemented sands found deeper in the Willis Formation. We drill a borehole, isolate a test section with packers, and apply a constant or falling head while recording flow rates. The data feeds directly into dewatering plans, seepage analyses, and slope stability evaluations where pore pressure is a key variable. We also use these results to calibrate numerical models for consolidation settlement under large embankments or building loads.
Technical reference image — Houston
Local considerations
IBC 2021 and ASCE 7-22 both require site-specific groundwater information for any structure in Seismic Design Category C or higher. In Houston, where the water table can rise within 1.5 m of the surface after heavy rain, ignoring in-situ permeability leads to two common failures: buoyancy uplift on shallow foundations and excessive seepage through basement walls. The Lugeon test is especially relevant here because the stiff clay layers often contain silt seams that act as preferential flow paths — a standard lab test on a small sample misses these entirely. Without a field permeability test, your drainage design is a guess, and that guess can cost millions in post-construction remediation.
Lefranc (constant head / falling head) — Lugeon (packer test)
Typical depth range
2 m to 50 m (up to 100 m with high-pressure packers)
Hydraulic conductivity range measured
1×10⁻⁵ m/s to 1×10⁻¹⁰ m/s
Borehole diameter
NX (76 mm) to HQ (96 mm) standard
Packer type
Single or double pneumatic packers (ASTM D5092)
Data recorded
Flow rate, pressure, time, water temperature
Reporting
k vs. depth profile, transmissivity, anisotropy ratio
Associated technical services
01
Lefranc Permeability Test (Shallow)
Designed for the upper 10 m of the profile, where Beaumont sands and silty clays dominate. We use a falling head setup in a cased borehole, measuring flow until steady state. Typical applications include detention pond liner evaluation, dewatering design for shallow excavations, and septic system siting. Results are reported as k in m/s with a confidence interval.
02
Lugeon Packer Test (Deep / Bedrock)
Applied in the deeper Willis Formation claystones and cemented sands, or when drilling into the Yegua Formation sandstone. We isolate a 1.5 m test interval with a double packer and apply incremental pressure stages (low to high to low). This test identifies joint-controlled flow and provides Lugeon units (1 Lugeon = 1×10⁻⁷ m/s). Commonly used for dam foundations, deep basements, and tunnel seepage assessments.
03
Constant Head Permeability Test (Saturated Zone)
Used below the water table in relatively uniform sand layers. We maintain a constant water level in the borehole and measure the steady inflow rate. This method is preferred for dewatering system design and for verifying hydraulic conductivity assumptions in groundwater models. All data is cross‑checked against grain‑size correlations from the same borehole.
Applicable standards
ASTM D5092-21 (Standard Practice for Design and Installation of Groundwater Monitoring Wells), ASTM D6391-11 (Field Measurement of Hydraulic Conductivity Limits of Porous Materials), IBC 2021 Section 1803.5.4 (Groundwater data requirements), FHWA NHI-10-016 (Soil Nailing, seepage control)
Frequently asked questions
How much does a field permeability test cost in Houston?
A standard Lefranc or Lugeon test in the Houston area typically runs between US$560 and US$1,030 per test interval. This includes mobilization, drilling supervision, packer setup, data collection, and a certified report. The final price depends on depth, number of intervals, and site accessibility. Contact us for a firm quote based on your specific borehole layout.
How is a field permeability test different from a lab falling head test?
Lab tests use a small, disturbed sample — typically a 3-inch Shelby tube — that may not represent the natural soil fabric, especially if silt seams or macro-pores are present. A field permeability test measures the actual soil mass in place, including fissures, laminations, and root channels. In Houston's heterogeneous alluvium, field values can be 10 to 100 times higher than lab results.
When should I request a Lugeon test instead of a Lefranc test?
Use the Lugeon method when you are testing rock or very stiff clay where joint flow dominates. The Lugeon test applies controlled pressure (up to 10 bar) to force water into fractures, giving you a Lugeon value that correlates directly with grouting needs and dam foundation design. The Lefranc test is better for soils — sands, silts, and soft clays — where gravity flow is the main mechanism.
Can the test be performed in existing boreholes or monitoring wells?
Yes, as long as the borehole is open and the screen or casing does not interfere with the test interval. We can run a single‑packer test in an uncased hole or a double‑packer test inside a PVC‑cased well with a slotted screen. We do recommend a check of the well development history first, because fines migration from poor development can artificially lower the measured permeability.
Location and service area
We serve projects across Houston and its metropolitan area.
