Glasgow’s ground doesn’t give up its secrets easily. Between the relentless rainfall—over 1,100 mm annually—and a subsurface carved out by glacial retreat, water moves through the soil and rock in ways that desk studies rarely predict. We’ve seen sites in the Clyde valley where a metre of sandy till holds more water than the underlying bedrock, and others up in Drumchapel where the sandstone is tighter than expected. This is exactly where a field permeability test (Lefranc/Lugeon) stops being a tick-box exercise and becomes the backbone of a workable groundwater control plan. In our experience across Glasgow, combining in-situ hydraulic conductivity data with a CPT test profile often clarifies whether a perched water table or a deeper aquifer is driving the seepage, saving weeks of misdirected dewatering effort.
A single Lugeon test in Glasgow’s fractured sandstone can reveal more about inflow risk than a dozen lab tests on intact core.
Site-specific factors
Glasgow’s drift geology is a patchwork of lodgement till, glaciofluvial sand lenses, and laminated clays laid down by the last ice advance. The water table in the city centre often sits just 1.5 to 3 metres below ground level, and perched water is common where sand stringers are trapped within the till. The biggest risk we encounter is assuming a single permeability value across a site. An undetected sand lens in a cutting in Maryhill or a fractured sandstone zone in the Gorbals can turn a dry excavation into a sump within hours. Equally dangerous is underestimating bedrock permeability: we have measured Lugeon values above 30 in weathered sandstone near old mine workings, where grouting becomes essential before any deep foundation work. Skipping a field permeability test in these conditions means designing a dewatering system blind—and in Glasgow’s climate, the water always finds the path of least resistance.
Questions and answers
What is the difference between a Lefranc test and a Lugeon test?
A Lefranc test measures water permeability in unconsolidated soils—sand, gravel, silt, or glacial till—typically within a borehole or standpipe. It can be run as a constant-head or falling-head test. A Lugeon test is designed for fractured rock; it uses an inflatable packer to seal off a section of the borehole and injects water at controlled pressures. The result is expressed in Lugeon units, where 1 Lugeon approximates a permeability of 1×10⁻⁷ m/s. In Glasgow we often run both on the same project: Lefranc in the drift and Lugeon in the Carboniferous bedrock.
How much does a field permeability test cost in Glasgow?
For a typical Lefranc or Lugeon test programme in the Glasgow area, you can expect to invest between £500 and £930 per test point, depending on depth, access constraints, and whether a drilling rig is already mobilised on site. We provide a detailed breakdown before any work starts.
How long does a Lugeon test take to complete?
A single Lugeon test on a 5-metre interval typically takes about 90 minutes once the packer is set at depth. This includes the full five-stage pressure cycle and the recovery period. If we are testing multiple intervals in the same borehole, we can usually complete three to four tests in a standard working day, assuming stable hole conditions.
Can you test permeability in the boulder clay that is common around Glasgow?
Yes, absolutely. Glasgow’s boulder clay is a lodgement till with a silty-clay matrix, and its bulk permeability is generally low—often in the 10⁻⁹ to 10⁻⁷ m/s range. However, it frequently contains sand partings and fissures that create preferential flow paths. A falling-head Lefranc test in a carefully installed piezometer can capture this secondary permeability, which is often the controlling factor for excavation inflow.
What pressure do you use for a Lugeon test in Glasgow’s sandstone?
We follow BS EN ISO 22282-3 and limit the maximum test pressure to avoid hydraulic fracturing of the rock. In Glasgow’s Carboniferous sandstone, this is typically between 2 and 8 bar, depending on depth and the in-situ stress conditions. We always start with a low-pressure stage and monitor the flow-pressure curve; if we see signs of jacking or wash-out, we reduce the maximum pressure to keep the test within the laminar flow regime.
