Around Cheyenne, the contact between granite bedrock and weathered prairie soils creates drainage surprises on almost every project. You hit competent Sherman granite at 15 feet on the west side, then find sandy colluvium holding water near Crow Creek. That contrast makes assumptions about permeability expensive. We run in-situ tests because lab samples never capture fractures in rock or macropores in the fill. The Lugeon test in fractured granite gives you a real lugeon value before you commit to a grout curtain design. For shallow infiltration, the Lefranc method is faster and tells you exactly what the sandy silts can accept. When a Cheyenne project needs a permeability number, we bring the drill rig and the Mariotte bottle right to your site.
A Lugeon test in fractured Sherman granite gives you more than a number. It tells you what the grout will actually do.
Local ground factors
A detention basin off College Drive was designed using textbook infiltration rates for sandy loam. The owner skipped field testing. By August, the first monsoon storm left standing water for four days. The problem was not the soil texture. A thin caliche layer at four feet, invisible in the boring logs, was acting as a liner. We ran Lefranc tests at three depths and found the restriction immediately. The fix cost triple what the test would have. In Cheyenne, where evaporation rates often exceed precipitation and soils can hold salts cemented into hardpans, a single lab permeability test is not enough. You need the in-situ measurement. We see this pattern under roads, behind retaining walls, and beneath any structure where drainage matters.
Quick answers
How much does a field permeability test cost in Cheyenne?
For a standard Lefranc or single Lugeon test, budget between US$600 and US$930. The final number depends on depth, number of test intervals, and the drill rig time needed to advance the hole. We provide a fixed quote after reviewing your boring logs.
Which test is right for my project, Lefranc or Lugeon?
Lefranc for soil and heavily weathered rock. Lugeon for competent, fractured rock where you need to estimate grout take. If your Cheyenne site has both, we run Lefranc in the overburden and Lugeon in the granite, all in the same borehole.
How long does a Lugeon test take on site?
One test interval takes about 45 to 60 minutes of setup, pressure staging, and monitoring. If we test multiple intervals in a deep hole, the drill crew advances the hole between tests. A full day typically covers two to three intervals.
Can you test permeability in existing monitoring wells?
We can run a falling head test if the well is properly constructed with a short screen and an effective filter pack. For a Lugeon test, we need an open borehole in rock so we can isolate the interval with a packer.
