Field Permeability Testing (Lefranc/Lugeon) in Sioux City

At 1,200 feet above sea level along the Missouri River, Sioux City sits on a layered profile of loess-mantled bluffs and alluvial floodplain deposits. Permeability here is anything but uniform. A routine infiltration test in the Floyd River valley can show conductivity three orders of magnitude higher than what you get in the compacted glacial till under the bluffs. That contrast matters when you are designing a retention basin near Bacon Creek or evaluating underdrain capacity for a commercial lot on Gordon Drive. We run in-situ permeability testing using Lefranc procedures in boreholes and Lugeon tests in bedrock, following ASTM D6391 and USBR guidelines. The data we deliver feeds directly into dewatering plans, cutoff wall specifications, and groundwater modeling without relying on recompacted lab samples that rarely represent field conditions.

A Lefranc test in undisturbed loess often shows vertical conductivity 10 times higher than horizontal — you miss that entirely with a lab falling-head test.

Methodology and scope

In the loess deposits above the Missouri River bluffs, we often see vertical permeability an order of magnitude higher than horizontal due to root casts and desiccation cracks — a behavior you completely miss with remolded lab tests. Our Lefranc tests capture that anisotropy using variable-head and constant-head configurations in open boreholes, typically at 5-foot depth intervals. When we hit the bedrock beneath the till — usually Cretaceous shale or limestone — we switch to the Lugeon method, packing off 10-foot zones and injecting water at stepped pressures. For projects requiring shallow bearing capacity verification alongside permeability data, we coordinate with plate load test crews to minimize site visits. The packer seal integrity is checked at every stage; a leaky seal around a fractured shale zone will give you a conductivity number that is useless for grouting design. We also correlate the Lugeon values with RQD from rock core to identify open joints needing treatment. For deeper groundwater profiling, pairing the Lefranc data with resistivity tomography helps map preferential flow paths across the site.

Local ground factors

We reviewed a project near the Big Sioux River confluence where the contractor skipped field permeability testing and used generic lab values from a borrow source. Three months after the stormwater vault went in, groundwater buoyancy lifted the empty structure two inches out of alignment. In Sioux City’s Missouri River corridor, the water table can rise fast after spring melt and heavy rain events, turning a moderately permeable silt into a fully saturated hydraulic connection. Ignoring in-situ in-situ permeability values during the design phase leads to undersized sump pumps, failed cutoff walls, and infiltration basins that overflow during the first wet season. We measure the actual hydraulic conductivity where the soil sits, under natural stress and saturation, so your drainage model reflects reality — not an optimistic table from a textbook.

Typical values

Parameter	Typical value
Test Methods	Lefranc (soil) / Lugeon (rock)
Applicable Standards	ASTM D6391, USBR 6510, USACE EM 1110-2-1901
Borehole Diameter	NX or HX, depending on depth
Lugeon Packer Type	Single or double pneumatic packer
Test Interval Depth	1.5 to 3.0 m vertical spacing
Pressure Steps	5 typical (low-medium-high-medium-low)
Measurement Accuracy	±5% flow meter resolution
Reporting Unit	cm/s or Lugeon units (1 Lu ≈ 1.3×10⁻⁵ cm/s)

Complementary services

Lefranc Testing in Overburden

Variable-head and constant-head tests in boreholes through loess, alluvium, and glacial till. We target specific strata identified during drilling to isolate the hydraulic conductivity of each unit, providing accurate k-values for dewatering design and seepage analysis in the Missouri River basin.

Lugeon Testing in Bedrock

Packer testing in 10-foot intervals within Cretaceous shale and limestone formations common to the Sioux City uplands. We use five-step pressure cycles to detect fracture dilation, washout, and turbulent flow effects that influence grout curtain design and dam foundation evaluation.

Common questions

What is the typical cost of a Lefranc or Lugeon test in Sioux City?

Field permeability testing in Sioux City typically ranges from US$600 to US$1,140 per test interval. The final cost depends on borehole depth, number of test zones, access conditions along the loess bluffs or river bottomlands, and whether single or double packer setups are needed for the Lugeon procedure.

How many Lugeon pressure steps do you run per interval?

We run five pressure steps per isolated interval. The sequence goes low, medium, high, medium, low. This pattern reveals fracture dilation or clogging behavior — if the Lugeon value at the last low step is higher than the first, the rock mass is opening up under pressure, which directly affects the grouting strategy.

When do you recommend a Lefranc test over a lab permeameter?

We recommend a Lefranc test whenever the soil fabric matters — loess with root holes, varved clays, or sandy lenses in till. A lab permeameter test on a 2-inch sample cannot capture the macropores and layering that control field permeability. The Lefranc test measures the soil in place, under natural confining stress and with all its heterogeneities intact.