Allentown sits at about 338 feet above sea level in the Lehigh Valley, where the underlying geology is a mix of shale, limestone, and glacial till. That combination produces soils with highly varying hydraulic conductivity — from tight clays in the floodplains to coarser sands along the Little Lehigh Creek. We run falling and constant head laboratory permeability tests to measure that conductivity directly, giving you the k-value needed for dewatering design, slope seepage analysis, or foundation drainage layers. In our experience, soils here often behave differently than textbook values suggest, so site-specific lab data is non-negotiable. Before finalizing any excavation plan, we typically cross-reference results with a field permeability test to capture in-situ conditions, and when dealing with layered deposits, we combine lab data with resistivity surveys to map preferential flow paths.
Falling head tests on Allentown glacial tills consistently yield k-values between 10⁻⁵ and 10⁻⁷ cm/s, confirming low drainage potential.
Method and coverage
What we see most in Allentown is that the glacial till contains enough fines to make constant head tests unreliable — the flow is simply too slow. So for silty clays and compacted tills, we default to the falling head method, which measures permeability in the range of 10⁻⁵ to 10⁻⁷ cm/s with good accuracy. The constant head setup is reserved for clean sands and gravelly zones where flow rates are higher, typically above 10⁻³ cm/s. Our lab procedure follows ASTM D2434 for constant head and a modified falling head protocol for low-permeability specimens. We also run the test on remolded samples at target densities and moisture contents — useful when you are evaluating compacted clay liners or subgrade stabilization options. For projects involving retaining walls, knowing the drainage capacity of the backfill is critical, so we include the k-value directly in our report alongside grain size and Atterberg limits.
Technical reference image — Allentown
Regional considerations
The seasonal water table in Allentown can swing 5 to 8 feet between spring snowmelt and late summer, which directly affects the reliability of lab permeability values if sampling timing is off. A sample taken in March may show higher moisture content and lower density than one taken in August, skewing the k-value. We always document the sampling date and field moisture content so you can apply a correction factor for design. When the lab results indicate very low permeability (below 10⁻⁶ cm/s), we recommend verifying with an infiltration test at the site to confirm that drainage assumptions hold under real conditions.
For silts, clays, and compacted tills. Measures k-values from 10⁻⁵ to 10⁻⁷ cm/s using a flexible wall permeameter. Includes saturation, consolidation, and staged gradient testing.
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Constant Head Permeability (Granular Soils)
For clean sands and gravels. Uses a rigid wall cell with steady-state flow. Reports k-value at relative densities of 50%, 70%, and 90%.
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Remolded Specimen Permeability
Test on compacted samples at target moisture and density. Ideal for evaluating clay liners, subgrade layers, or backfill for MSE walls.
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Custom Permeability with Effective Stress
Falling or constant head test under controlled effective confining stress (5–30 psi). Simulates in-situ stress conditions for deep foundations or embankment design.
Standards that apply
ASTM D2434-19 (Constant Head Permeability of Granular Soils), ASTM D5084-16a (Falling Head Permeability of Fine-Grained Soils), ASTM D2487-17 (Classification of Soils for Engineering Purposes)
Quick answers
What is the difference between falling head and constant head permeability tests?
Falling head is used for low-permeability soils (clays, silts) where water flows slowly through the specimen; the head decreases over time. Constant head is for granular soils (sands, gravels) where flow is steady and the head is kept constant. Both follow ASTM standards and yield k-values in cm/s.
How much does a laboratory permeability test cost in Allentown?
A standard falling or constant head test typically ranges from US$400 to US$550 per sample. The final price depends on specimen size, number of confining pressures, and whether remolding is required. Contact us for a quote based on your project scope.
Do you test on undisturbed or remolded samples?
We accept both. Undisturbed Shelby tube samples are preferred for natural soil permeability. Remolded specimens are used when evaluating compacted fills, liners, or subgrade layers. The choice affects the k-value, so we always note the sample type in the report.
What ASTM standard do you follow for permeability testing?
We follow ASTM D2434 for constant head tests on granular soils and ASTM D5084 for falling head tests on fine-grained soils. Both are recognized by the International Building Code (IBC) and are accepted by Allentown building officials.
How long does a permeability test take?
A constant head test on sand takes 4 to 8 hours. Falling head tests on clay can take 24 to 48 hours due to slow flow rates. We provide preliminary results within 3 business days; the full report including grain size and Atterberg limits takes 5 to 7 days.
Location and service area
We serve projects across Allentown and its metropolitan area.
