When a Fort Wayne excavation hits saturated silty clay at twelve feet and the contractor’s sump pumps can’t keep up, the conversation shifts quickly from schedule to soil behavior. In the glacially overridden terrain that defines northeastern Indiana, the hydraulic conductivity of subsurface materials can vary by orders of magnitude within a single site. That variability makes field permeability testing — specifically the Lefranc and Lugeon methods — a practical necessity for any project that involves basements, retention ponds, or cut-and-cover construction. Rather than relying on lab-derived estimates that often miss the influence of fissures, sand lenses, or weathered till fabric, these in-situ tests measure how water actually moves through the formation. For a city where the Maumee River’s floodplain and its tributary terraces present distinct groundwater regimes, having site-specific permeability data before submitting a stormwater management plan to the Allen County Department of Planning Services saves both time and excavation headaches. We often pair field permeability with a grain-size analysis to confirm whether fines migration explains a lower-than-expected Lugeon value in silt-dominated intervals.
A single in-situ permeability measurement near a sump or creek bank provides more actionable design data than a shelf full of remolded laboratory samples.
Our approach and scope
Local geotechnical context
ASCE 7 and the IBC require that foundation designs account for groundwater buoyancy and seepage forces, yet the default hydrostatic assumptions often prove conservative — or dangerously unconservative — when the actual permeability of a Fort Wayne glacial till is unknown. A basement slab designed without measured hydraulic conductivity can underestimate uplift pressures during a spring high-water event, while an infiltration basin sized with a textbook infiltration rate may fail to drain within the 48-hour drawdown window required by the City of Fort Wayne Stormwater Management Ordinance. The Lefranc and Lugeon methods reduce that uncertainty by producing point-specific k-values that feed directly into finite-element seepage models. When the test is run in a properly developed piezometer, the results also reveal boundary effects like a nearby creek or retention wall that alter the local flow net. Skipping field permeability because a lab falling-head test on a Shelby tube sample seemed sufficient has led to more than one flooded excavation along the St. Marys River — a risk that a single morning of in-situ testing could have priced into the dewatering plan from the start.
Reference standards
ASTM D6391-11, ASTM D4630-19, USBR 7300-89, City of Fort Wayne Stormwater Management Ordinance
Complementary services
Lefranc Constant-Head Testing
Performed in soil boreholes or standpipe piezometers; water is added to maintain a steady head while flow rate is recorded. Ideal for sandy outwash, silty till, and man-made fill where moderate permeability controls dewatering requirements.
Lugeon Packer Testing in Rock and Hard Till
Uses a single or double packer to isolate a test interval, with water injected at five progressively increasing and decreasing pressure stages. The resulting pressure-versus-take curve characterizes fracture flow, dilation, and infill behavior in the limestone and dolostone bedrock that underlies much of Allen County.
Data Interpretation and Seepage Modeling Input
Raw pressure and flow data are reduced to hydraulic conductivity values with corrections for temperature, viscosity, and packer compliance. Results are formatted for direct import into SEEP/W, MODFLOW, or PLAXIS groundwater models, supporting dewatering design and permanent drainage system sizing.
Typical parameters
Quick answers
What is the difference between the Lefranc test and the Lugeon test?
The Lefranc test measures hydraulic conductivity in soil or very soft rock by adding or removing water from a borehole cavity, typically under a constant or falling head. The Lugeon test is designed for rock and hard till: water is injected under pressure into an isolated interval sealed by packers, and the flow rate is measured at several pressure steps. Lefranc is suitable for unconsolidated glacial deposits common in Fort Wayne; Lugeon applies when the borehole encounters limestone or dolostone bedrock below the drift.
How much does field permeability testing cost in Fort Wayne?
When does the City of Fort Wayne require in-situ permeability testing?
The Allen County Department of Planning Services and the City of Fort Wayne Stormwater Management Ordinance often require field-measured infiltration rates for stormwater basins, rain gardens, and other green infrastructure. In-situ testing is also required when dewatering plans must demonstrate that proposed pumping rates will achieve drawdown without causing settlement or affecting adjacent structures.
How long does a single Lefranc or Lugeon test take?
A single Lefranc test at one depth typically requires 45 to 90 minutes once the borehole is prepared, including stabilization time to confirm steady-state flow. A full five-stage Lugeon test in rock can take two to three hours per interval because each pressure stage must be held until the flow rate stabilizes. Multiple tests can be run in one day if the borehole is logged and cleaned efficiently.
Can field permeability results be used directly in a dewatering or seepage model?
Yes. The hydraulic conductivity values derived from Lefranc and Lugeon tests are point-specific but, when combined with stratigraphic logs and a CPT profile or grain-size data, they provide the input parameters for finite-element seepage models such as SEEP/W or MODFLOW. The data also help calibrate the model against observed groundwater levels, improving the reliability of drawdown predictions.