Lubbock sits on the High Plains, and anyone who's broken ground here knows the subsurface doesn't give up its secrets easily. The IBC and ASCE 7 set the framework, but what you actually find in a trench depends on the paleo-playa deposits and that notorious caliche cap. When we excavate an exploratory test pit in Lubbock, we're not just checking a box on the permit application. We're looking at the contact between the reddish Brownfield clay and the underlying Ogallala Formation, measuring the thickness of that cemented hardpan that can fool a drill rig into thinking it hit refusal. A plate load test can later confirm bearing values, but the test pit gives us the stratigraphic context that no borehole log fully captures, especially in the transition zones between the draws and the flat uplands where the soil profile changes within a single lot.
You can't see the caliche variability from a boring log—you have to stand in the pit and look at the contact.
Common questions
How much does an exploratory test pit cost in Lubbock?
For a standard residential test pit in Lubbock, you're typically looking at US$510 to US$930, depending on depth, access, and whether we're dealing with heavy caliche that slows the excavator down. That price includes the machine time, the engineering log with photos, and the final report signed by the geotechnical engineer. If we're doing multiple pits on the same lot or combining it with a drilling program, the per-pit cost drops.
How deep do you dig a test pit for a typical Lubbock slab-on-grade foundation?
For most single-family residential work inside the Loop and in the newer subdivisions south of 98th Street, we excavate to 8 or 10 feet below existing grade. That gets us through the entire active zone of the expansive clay and into the caliche or the upper Ogallala, which is what the IBC requires for a site-specific investigation.
Do I need a test pit if I already have SPT borings on the same site?
They complement each other. An SPT boring gives you blow counts and a disturbed sample every few feet; a test pit gives you a continuous, undisturbed view of the stratigraphy across the full trench wall. In Lubbock, where the caliche can be discontinuous, we've found boulders or solution cavities in a test pit that a boring drilled right past.
What happens if you hit groundwater during the test pit excavation?
On the High Plains, true groundwater is deep—often 100 feet or more. What we do encounter in Lubbock test pits is perched water, usually after heavy rain or irrigation, sitting on top of a clay lens. If we find it, we log the depth, note the seepage rate, and collect a water sample for sulfate and pH testing if the foundation design calls for sulfate-resistant cement.
How quickly can you schedule a test pit and deliver the report?
Normally we can have the excavator on site within three to five business days of the signed authorization. The field log and photos go to the client the same day, and the sealed engineering report follows within a week. If you're on a tight construction schedule, we can expedite the report for a next-day turnaround.
