Field Permeability Test (Lefranc/Lugeon) in Allentown

A mid-rise condo project on Hamilton Street hit a snag when excavation started: groundwater seeped into the pit faster than expected. Without knowing the in-situ permeability of the Lehigh Valley alluvial deposits, the dewatering design was a guess. That is exactly why we run field permeability tests in Allentown before foundation work begins. Using the Lefranc constant-head method for granular soils and the Lugeon packer test for rock, we measure hydraulic conductivity directly in the ground. For projects near the Little Lehigh Creek, where perched water tables are common, this data is non-negotiable. It prevents surprises during excavation and saves weeks of schedule delays. We also cross-check results with laboratory permeability tests on undisturbed samples to validate the field numbers against controlled conditions.

In Allentown's variable glacial till and limestone bedrock, field permeability is the only reliable way to predict groundwater behavior before breaking ground.

Method and coverage

Allentown sits on a mix of glacial till, limestone bedrock, and river-deposited sands along the Lehigh River. The water table in the downtown corridor typically sits 8 to 15 feet deep, but in spring it can rise sharply. Our field permeability test uses a single-borehole setup with constant-head or falling-head readings depending on soil gradation. We follow ASTM D5092 for test execution and data reduction. The procedure involves:

Drilling a 3-inch borehole to the target depth
Installing a screened casing or inflatable packer
Measuring flow rate under a steady head for 30-60 minutes

Results are expressed in cm/s or ft/day. For rock sections, the Lugeon method applies pressure increments from 0.1 to 1.0 MPa to identify fissure flow. This data feeds directly into dewatering design, slope drainage, and infiltration system sizing for stormwater management plans required by Lehigh County.

Regional considerations

Allentown experiences an average of 44 inches of rainfall per year, well above the national average, and snowmelt in late winter saturates the ground. In limestone areas, solution channels can create erratic permeability — one borehole may show tight clay while another hits an open fissure. Relying solely on lab tests from small core samples misses these features. A field permeability test in Allentown captures the real behavior of the rock mass or soil horizon. We have seen contractors budget for simple sump pumps only to face full-scale dewatering systems mid-project. That cost overrun is avoidable with one day of In-Situ before the excavator arrives.

Technical parameters

Parameter	Typical value
Test method	Lefranc (constant/falling head) or Lugeon (packer)
Permeability range	1×10⁻⁷ to 1×10⁻¹ cm/s
Borehole diameter	3 to 6 inches (76-152 mm)
Test duration	30-90 minutes per depth
Typical depth range	5 to 50 feet
Reported output	k (hydraulic conductivity) in cm/s or ft/day, flow regime notes

Complementary services

Multi-Level Packer Testing

For deep foundations or tunnel alignments, we use inflatable packers to isolate discrete zones in a single borehole. This identifies permeable layers at different depths — critical when designing grout curtains or deep drainage systems in the Lehigh Valley's layered geology.

Falling-Head Permeability in Soft Soils

In the clay-rich glacial till found in west Allentown, constant-head tests can take hours to stabilize. The falling-head method accelerates the test while maintaining accuracy. We run it with a sealed standpipe and data logger for continuous readings, giving you results by the next business day.

Standards that apply

ASTM D5092-04 (Standard Practice for Design and Installation of Groundwater Monitoring Wells), ASTM D6391-11 (Field Measurement of Hydraulic Conductivity Limits of Porous Materials), USBR 7300-89 (Lugeon Test Procedure for Rock), IBC 2018 Section 1806 (Presumptive Load-Bearing Values, referencing groundwater)

Quick answers

What is the difference between the Lefranc and Lugeon field permeability tests?

The Lefranc test is used in soils and uses a constant or falling head of water in a screened borehole. The Lugeon test is designed for rock and uses a packer to isolate a section, then applies pressure increments to measure flow under increasing head. Both follow ASTM D5092 procedures but serve different ground conditions.

How much does a field permeability test in Allentown cost?

A single-depth field permeability test in Allentown typically ranges between US$590 and US$1,000, including setup, on-site execution, and a full data report. Costs increase if multiple depths or packer assemblies are required. Contact us for a project-specific quote.

When is a field permeability test required instead of a lab test?

Field tests are essential when groundwater control, dewatering design, or infiltration system sizing is critical. Lab tests on small samples cannot represent fissures, stratification, or large-scale flow paths. For any project in Allentown where the water table is within 15 feet of excavation depth, we recommend field testing over lab-only.

Can you run a field permeability test on a tight construction schedule?

Yes. We can mobilize to an Allentown site within 48 hours of confirmation. A typical single-depth Lefranc test takes half a day, including drilling and readings. Results are delivered within 2 business days. For multi-depth or Lugeon tests, add one day per three test intervals.