San Bernardino grew fast after the railroad arrived in the 1880s, and that expansion pushed development onto alluvial fans and old river terraces. The soils here are a mix of sandy loams, silts, and gravelly deposits from the Santa Ana River watershed. For any new construction, knowing how fast water moves through the ground is critical. We run the double-ring infiltrometer and Porchet method to measure percolation rates directly in the field. That data drives drainage design, septic system sizing, and stormwater infiltration basins. Before we start, we often pair the infiltration test with a dilatometer test to understand lateral stress and stiffness of the deeper strata. Then we cross-check results against the permeability lab test for a complete hydraulic picture.
In San Bernardino, dry-season infiltration rates can be 3 to 5 times higher than wet-season rates due to desiccation cracking and soil crusting.
Approach and scope
The climate here is semi-arid, with most rain falling between November and March. That dry spell means the near-surface soils can develop a hard crust or even slight desiccation cracks. An infiltration test run in July gives very different numbers than one run in February. We always note the antecedent moisture condition and adjust our interpretation accordingly. The Porchet method works well for shallow percolation in uniform soils, while the double-ring infiltrometer isolates vertical flow and minimizes lateral spreading. Both follow ASTM D3385-18. We record the falling head over time and calculate the saturated hydraulic conductivity (Ksat). When the site has layered soils, we add a veleta field test to check undrained shear strength in the clay lenses. And if collapsible soils are suspected, we run the collapsible soil test on undisturbed samples. The combination gives us a complete hydro-mechanical profile.
Technical reference image — San Bernardino
Site-specific factors
Compare the alluvial fans near the foothills of the San Bernardino Mountains with the flat valley floor near the Santa Ana River. The fans drain quickly — Ksat values often exceed 10⁻³ cm/s. Down in the river terrace, fine silts and clay layers can drop that to 10⁻⁵ cm/s or lower. If you design a detention basin based on fan data but build on terrace soils, the basin will not drain fast enough. That leads to standing water, foundation moisture problems, and even slope instability on the embankment. We have seen it happen. That is why we run the infiltration test at multiple locations across the site, not just one borehole. The spatial variability in San Bernardino is real, and ignoring it is a risk.
Standard ASTM D3385-18 for percolation rates in low-permeability soils. 60 cm outer ring, 30 cm inner ring. Ideal for detention basin design and stormwater infiltration systems.
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Porchet (Falling Head) Method
Single-ring falling head test for rapid assessment of sandy and gravelly soils. Quick setup, reliable for septic system sizing and shallow drainage applications.
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Multi-Depth Infiltration Profile
Infiltration tests at 0.5 m, 1.0 m, and 1.5 m depths to capture vertical variability. Includes soil texture analysis and moisture condition report.
Relevant standards
ASTM D3385-18: Standard Test Method for Infiltration Rate of Soils in Field Using Double-Ring Infiltrometer, ASTM D2434-19: Standard Test Method for Permeability of Granular Soils (Constant Head), IBC 2021 Chapter 18: Soils and Foundations, Section 1803.5.10: Infiltration testing
Quick answers
How long does an infiltration test take in San Bernardino?
Typically 2 to 6 hours per test point. Sandy soils on the alluvial fans can be done in under 3 hours. Clayey terrace soils near the Santa Ana River may need up to 6 hours to reach steady-state flow. We schedule morning starts to avoid afternoon heat.
What is the difference between double-ring and Porchet methods?
The double-ring infiltrometer uses two concentric rings to isolate vertical flow and minimize lateral spreading. The Porchet method uses a single ring and is simpler, but it can overestimate Ksat in layered soils. We choose based on site conditions and project requirements.
Does the infiltration test need to be done before or after grading?
Before grading is ideal, because the natural soil structure and crust are undisturbed. If grading has already cut or filled the site, we test in the proposed finished grade elevation. We note the disturbance in the report.
How much does an infiltration test cost in San Bernardino?
The typical range is between US$320 and US$440 per test point. Volume discounts apply for multi-point testing on large sites. The final quote depends on depth, access, and number of locations.
