Whitby’s expansion from a modest lakefront settlement into a key node in Durham Region has placed increasing demand on its underlying geology. The interplay between dense Halton Till, fractured Georgian Bay shale, and sandy lake-bottom deposits creates a hydrogeological profile that varies sharply across the town—from the rolling drumlins north of Taunton Road to the flatter terraces near Port Whitby. When a project intersects the local water table, which sits within 2 to 4 metres of surface across much of the municipality, the hydraulic conductivity of these units dictates everything from excavation stability to long-term basement drainage. A CPT test can map stratigraphy, but only the Lefranc and Lugeon field permeability tests provide the direct k-values required for seepage analysis and dewatering system design under the Ontario Building Code.
A single Lugeon stage in fractured Georgian Bay shale often reveals more about excavation water inflow than a dozen grain-size correlations ever could.
Technical details of the service in Whitby
Demonstration video
Typical technical challenges in Whitby
The Iroquois Beach commercial redevelopment area illustrates the consequences of bypassing in-situ permeability testing. A multi-storey structure with a two-level underground parking garage was designed using k-values derived from grain-size correlations on split-spoon samples. During the first major spring melt after construction, groundwater inflow through a fractured shale seam in the ramp access exceeded the sump pump capacity, flooding the lower level and damaging electrical rooms. The post-incident Lugeon testing we performed showed a permeability two orders of magnitude higher than the design assumption. In Whitby, where the bedrock surface is an erosional unconformity riddled with open joints and where overburden ranges from tight till to permeable outwash, assuming hydraulic conductivity from borehole logs is a gamble. A Lefranc test in the excavation base and a Lugeon profile in the bedrock socket cost a fraction of the remediation bill for a flooded garage.
Our services
Our field testing program in Whitby covers the full range of in-situ permeability measurement, executed from truck-mounted rigs with experienced drillers who understand the local geology. Each test includes a detailed borehole log, pressure-flow data, and a signed report from the supervising geotechnical engineer.
Lefranc Permeability Testing (Soil)
Constant-head or falling-head Lefranc tests in overburden soils. We isolate the test zone with a screened casing and measure flow rates with a precision flowmeter, computing k-values directly from the steady-state condition. Ideal for dewatering design in the sandy interbeds common to Whitby’s drumlinized till plains.
Lugeon Permeability Testing (Rock)
Multi-stage pressure testing in bedrock using a single-packer assembly. We run five pressure increments per stage and plot the pressure-flow relationship to classify flow regime (laminar, turbulent, dilation, washout). This method is critical for assessing water inflow into excavations in the Whitby Formation shale.
Frequently asked questions
What is the typical cost range for a Lefranc or Lugeon test in Whitby?
For a single Lefranc or Lugeon test stage in the Whitby area, budgets typically fall between CA$880 and CA$1,370. The exact cost depends on borehole depth, number of pressure stages, and whether the test is stand-alone or integrated into a broader site investigation program. All quotes include the technical report with calculated k-values and pressure-flow curves.
How many Lugeon stages are needed for a typical excavation in Whitby shale?
We recommend a minimum of three Lugeon stages per borehole for excavations that penetrate the Georgian Bay Formation: one stage in the upper weathered zone (typically 1–3 m below bedrock surface), one in the intermediate competent rock, and one at the proposed excavation base. This vertical profile captures the sharp permeability contrast that often exists between the fractured upper bedrock and the more intact lower mass.
Can the Lefranc test be performed in the same borehole as an SPT or CPT sounding?
Yes, and in most cases we do. The borehole is advanced through the overburden with standard penetration testing or CPT profiling to establish stratigraphy, and the Lefranc test zone is then isolated at the target depth using a screened casing or packer. This integrated approach reduces mobilization costs and provides a complete dataset—strength, stratigraphy, and permeability—from a single borehole location.