A contractor excavating for a new subdivision near Bowmanville kept hitting water at 3 meters. The silty till looked dense, but the inflow suggested fractures and lenses. They needed a real permeability value, not a guess from grain-size curves. Our team mobilized within 48 hours to run a series of in-situ tests. Clarington’s glacial stratigraphy makes permeability highly variable, and the only reliable approach is a field permeability test that isolates the specific horizon. We ran Lefranc tests in the shallow till and one Lugeon test in the underlying shale bedrock to confirm the grouting program. The result: the contractor adjusted dewatering and saved two weeks on the schedule.
A Lugeon value below 3 means grouting can be optimized; above 10, the curtain design needs revision.
Methodology and scope
Local ground factors
Soil conditions between Courtice and rural Clarington tell two different stories. Near the Lake Ontario shoreline, silty sand and clayey silt dominate, with groundwater barely two meters down. A Lefranc test there often reveals k values high enough to require wellpoint dewatering. Head north toward the moraine, and the till tightens up, but fractures in the shale bedrock can still transmit significant flow. One developer learned this the hard way in Newcastle: they assumed low permeability based on grain-size analysis, skipped field testing, and faced a flooded excavation that delayed the foundation pour by three weeks. The Lugeon test we ran afterward showed a k of 5×10⁻⁴ cm/s in the upper bedrock, which meant the original sump-pumping plan was undersized by a factor of four. In Clarington’s layered geology, lab estimates alone are a gamble.
Relevant standards
ASTM D6391-11: Standard Test Method for Field Measurement of Hydraulic Conductivity Using Borehole Infiltration (Lefranc), ASTM D4630: Standard Test Method for Determining Permeability of Rocks by the Constant Head Injection Method (Lugeon), and the Canadian Foundation Engineering Manual (CFEM) 5th ed., Chapter 4: Groundwater and Permeability.
Associated technical services
Lefranc Variable-Head Tests
Designed for soil and weathered rock horizons. We measure the rate of water level recovery in a cased borehole to calculate hydraulic conductivity. Ideal for dewatering design in the silty deposits common across Bowmanville and Courtice.
Lugeon Pressure-Packer Tests
Applied in competent bedrock, typically the Lindsay and Verulam formations underlying Clarington. Five-stage pressure testing quantifies fracture flow and guides grout curtain design for deep excavations and cut-and-cover tunnels.
Combined Soil-Rock Permeability Profiles
A single borehole program covering both overburden and bedrock. We sequence Lefranc and Lugeon tests in the same hole, delivering a continuous permeability log for projects where groundwater control spans both materials.
Typical parameters
Common questions
What is the difference between the Lefranc and Lugeon test?
The Lefranc test measures hydraulic conductivity in unconsolidated soils or heavily weathered rock using a falling or constant head in a standpipe. The Lugeon test is specifically for fractured rock; water is injected under pressure through a packer-sealed interval, and the flow rate at each pressure stage is interpreted to estimate rock mass permeability (Lugeon units).
How long does a field permeability test take on a Clarington site?
A single Lefranc test usually takes 1 to 2 hours once the borehole is at depth. A full five-stage Lugeon test runs about 90 minutes for the pressure cycle. We typically schedule one day for two to three test intervals, including rig setup and washout between stages.
What is the typical cost for a Lefranc or Lugeon test in Clarington?
Can you run a permeability test in the same borehole as an SPT or rock coring?
Yes, that is standard practice. We advance the borehole with SPT sampling or coring, then set the packer at the desired depth and run the permeability test. This way you get both strength and hydraulic conductivity data from the same location, which simplifies site characterization.
What field permeability value would trigger the need for dewatering in this area?
In Clarington’s silty soils, a hydraulic conductivity above 1×10⁻⁴ cm/s usually means active dewatering, especially if the excavation goes below the Lake Ontario water table. Below 1×10⁻⁵ cm/s, sump pumping may be enough, but we always recommend a site-specific assessment because thin sand seams can change the behavior entirely.