Colorado Springs sits on a complex interface between the Pierre Shale, Dawson Arkose, and Quaternary alluvial deposits along Fountain Creek. This means hydraulic conductivity can vary by three orders of magnitude within a single project site. A standard lab perm won't capture fractures in the arkose or preferential flow paths in the sandy gravels. We run in-situ permeability tests because that's what the geology demands. The Lefranc method handles the unconsolidated overburden, and the Lugeon test protocol applies to the fractured sandstone bedrock found across the foothills west of I-25. Getting these numbers right determines dewatering scope, basement waterproofing design, and whether your infiltration basin will actually drain.
A Lugeon test in fractured Dawson Arkose often reveals permeability 10 to 50 times higher than intact core samples suggest. Field data prevents costly dewatering undersizing.
Technical details of the service in Colorado Springs
Risks and considerations in Colorado Springs
Colorado Springs experienced rapid population growth from 280,000 in 2000 to over 490,000 today, pushing development into the foothills where shallow bedrock and fractured aquifers complicate foundation drainage. Several landslide complexes in the Broadmoor area are driven by groundwater perched on weathered shale. Misjudging in-situ permeability leads to undersized underdrains, flooded excavations, and failed stormwater infiltration systems. If you are designing a retention pond over alluvium, and you assume a lab-derived k of 1E-5 cm/s when field tests show 1E-3 cm/s, the pond will drain 100 times faster than expected. For deep basements, we coordinate permeability testing with excavation monitoring to track actual inflow against design assumptions during construction.
Our services
The field permeability testing program for projects in Colorado Springs encompasses:
Lefranc Variable-Head Tests
In-situ hydraulic conductivity measurement in soil and weathered rock using a falling-head procedure. Ideal for alluvial terraces along Monument and Fountain Creeks.
Lugeon Packer Tests
Multi-stage pressure testing in competent and fractured rock. We apply the Houlsby interpretation for Dawson Arkose and Pikes Peak granite.
Dewatering Feasibility Studies
Combines field k-values with pumping test analysis to size well systems and predict drawdown for deep excavations and utility trenches.
Infiltration Testing
Double-ring infiltrometer and borehole permeameter tests per ASTM D3385 for stormwater BMP design compliance with El Paso County criteria.
Frequently asked questions
When does a project need a Lugeon test instead of a Lefranc test?
A Lugeon test applies when the rock RQD exceeds about 25% and the formation can hold a packer seal. In Colorado Springs, this typically means the Dawson Arkose or the granite west of Manitou Springs. The Lefranc test handles soil, weathered rock, and highly fractured zones where a packer won't seal.
How much does a field permeability test cost in Colorado Springs?
How do you account for variable water tables during testing?
We install a temporary piezometer adjacent to the test interval to monitor groundwater level throughout the test. For falling-head Lefranc tests, we correct for the saturated zone thickness. In Lugeon testing, we record the static water level and apply pressure corrections per the USBR procedure to isolate formation response from hydrostatic effects.
Can you test permeability in the Pierre Shale?
Yes, but with careful interpretation. The Pierre Shale is an aquitard with typical k-values in the 1E-7 cm/s range. Standard Lefranc tests often show near-zero flow. We use prolonged constant-head tests with high-precision flow meters to resolve the low conductivity, which is critical for landfill liner studies and containment berm design.