A common oversight we see from contractors in Riverside is assuming that the sandy loam and gravel layers under the city drain uniformly. After winter rains from the San Bernardino Mountains, perched water tables develop in zones of lower permeability, and a standard percolation test simply misses the variability. We have found that running a field permeability test (Lefranc or Lugeon) in these stratified alluvial deposits reveals the actual hydraulic conductivity layer by layer. That data is what prevents unexpected groundwater seepage during excavation for basements or utility trenches. It is also essential before designing any dewatering system or planning a grouting program to seal permeable lenses.
Testing in Riverside's alluvial fan deposits revealed permeability contrasts of up to three orders of magnitude within 10 vertical feet.
Method and coverage
The difference between soils near the Santa Ana River and those closer to Box Springs Mountain is night and day. Near the river, the deposits are coarser—sands and gravels with conductivities in the 10^-3 to 10^-4 m/s range—while the foothills contain more silt and clay, dropping to 10^-6 m/s or lower. For a Lefranc test in Riverside, we use a constant head setup when the water table is shallow and a falling head when it is deeper. The Lugeon test, run under stepped pressures in a packered borehole, is our go-to for evaluating fracture permeability in the granitic bedrock east of the city. Both methods follow ASTM D6391 and help us calibrate the seepage models that inform excavation support systems.
Technical reference image — Riverside
Regional considerations
IBC Section 1805 and ASCE 7 Chapter 14 both require that subsurface drainage systems be designed using measured hydraulic conductivity values. In Riverside, where the seasonal high groundwater can rise within 8–10 ft of the surface in low-lying neighborhoods like Arlington or La Sierra, relying on published tables instead of site-specific field permeability tests often leads to undersized drains or buoyancy failures in shallow foundations. We have seen retaining walls crack and slab-on-grade floors heave because the design team assumed a uniform drainage rate. Running a Lefranc or Lugeon test directly in the problematic stratum removes that guesswork and keeps the project compliant with local building codes.
Lefranc (constant/falling head) or Lugeon (step-pressure)
Hydraulic conductivity range
10^-3 to 10^-7 m/s
Borehole diameter
2 to 6 inches (NX or HQ)
Test section length
3 to 10 ft (packer interval)
Applied pressure (Lugeon)
Up to 150 psi in 3–5 steps
Applicable standard
ASTM D6391-11, USBR 5515
Complementary services
01
Lefranc Test in Overburden
Constant or falling head test performed in uncased boreholes through sands, silts, and gravels. Ideal for measuring vertical and horizontal conductivity in Riverside's alluvial fan deposits.
02
Lugeon Packer Test in Bedrock
Multi-pressure step test using an inflatable packer to isolate a 3–10 ft section. Best for evaluating fracture permeability in the granitic and metamorphic rock east of Riverside.
03
Rising/Falling Head Monitoring
Long-term monitoring of water level recovery in standpipes or observation wells after the test. Provides recession data for transient seepage analysis.
04
Seepage Modeling Report
We integrate the field test results with SEEP/W or similar software to produce flow nets, uplift pressures, and dewatering volume estimates tailored to your Riverside project.
Standards that apply
ASTM D6391-11 (Field permeability by constant/falling head), USBR 5515 (Lugeon test procedure for rock), IBC 2021 Chapter 18 (Soils and foundations), ASCE 7-22 Chapter 14 (Lateral earth pressures and groundwater)
Q&A
What is the difference between a Lefranc and a Lugeon field permeability test?
The Lefranc test is run in soil or soft rock using a constant or falling head under a single low pressure, measuring bulk hydraulic conductivity. The Lugeon test is a step-pressure packer test used in rock to evaluate fracture permeability and assess grouting needs. In Riverside, we choose Lefranc for alluvial soils and Lugeon for the fractured granitic bedrock.
How much does a field permeability test (Lefranc/Lugeon) cost in Riverside?
For a standard single-depth test, the cost typically ranges between US$540 and US$1,010, depending on access conditions, borehole depth, and whether a packer assembly is required. Multiple test intervals or additional monitoring visits will increase the total. Contact us with your site specifics for a firm quote.
At what depth do you run the test in Riverside's alluvial soils?
We usually place the test section between 5 and 30 feet below grade, targeting the most permeable layer identified from the soil log. If the water table is shallow, we start with a constant head test; if it is deeper than 15 ft, a falling head test is more practical. The exact depth is decided based on the geotechnical boring data.
What standard does the field permeability test follow?
We perform the test in accordance with ASTM D6391-11 for constant/falling head in soil and USBR 5515 for the Lugeon procedure in rock. The results are reported in cm/s or ft/day and can be used directly in IBC Chapter 18 drainage calculations and ASCE 7 groundwater uplift checks.
