A warehouse expansion off Coffee Road hit refusal at 12 feet with SPT; the contractor had no idea the loose layer below was even looser until we brought the CPT rig in. Bakersfield’s basin fill tells a story in every cone log—layers of sandy silts, old Kern River channel deposits, and occasional cemented lenses that stop a standard sampler cold. The cone penetration test measures tip resistance and sleeve friction continuously, giving you a profile that doesn’t miss the thin weak zones a split spoon skips every 5 feet. For Bakersfield projects where liquefaction screening drives the foundation design, that uninterrupted record matters. We run our CPT trucks out of a lab that also performs SPT drilling when borehole samples are required for index testing, so the field program fits the stratigraphy instead of the other way around.
Continuous cone resistance logs catch the thin weak layers that a 5-foot SPT interval misses—and in Bakersfield’s layered basin fill, those layers control settlement.
How we work
Local considerations
A common mistake we see on Bakersfield infill lots is running only SPT borings to 30 feet and calling it sufficient. The problem? SPT blow counts average out over 12 inches, so a 2-inch silt seam at 14 feet—exactly where the CPT shows a friction ratio spike—gets smeared into the “medium dense sand” classification. If that seam liquefies, differential settlement cracks tilt-up panels and breaks utility connections. CPT refusal also catches something Bakersfield drillers know well: the Pleistocene-age cemented lenses that feel like refusal but sit over still-compressible material. By reading cone resistance and sleeve friction simultaneously, we distinguish true bearing strata from false refusal. The cost of a supplemental CPT push is negligible next to re-designing foundations after excavation reveals what the borings missed.
Relevant standards
ASTM D5778-20 establishes the standard test method for electronic friction cone and piezocone penetration testing of soils, while ASTM D6067/D6067M-17 provides standard practice for using the electronic piezocone penetrometer. ASCE 7-22 defines minimum design loads and associated criteria for buildings and other structures, including site class considerations. The Robertson and Wride (1998) methodology offers a framework for cyclic liquefaction evaluation based on both SPT and CPT data, and the Caltrans Geotechnical Manual supplies CPT guidelines specific to transportation projects.
Associated technical services
Piezocone Penetration Testing (CPTu)
Full CPTu with pore pressure measurement for Bakersfield sites where groundwater affects liquefaction assessment. Includes dissipation tests at key depths, corrected cone resistance, and normalized soil behavior type charts. Ideal for sites within the Kern County subbasin needing seismic settlement analysis.
CPT-Based Foundation Parameter Report
Engineering report translating cone data into design parameters: undrained shear strength for clays, relative density for sands, constrained modulus for settlement calculations, and liquefaction screening per Boulanger & Idriss (2014) CPT-based procedure. Delivered with digital log files compatible with gINT and OpenGround.
Typical parameters
Common questions
How much does a CPT test cost in Bakersfield?
Can CPT completely replace SPT borings for a Bakersfield project?
CPT provides continuous stratigraphy and excellent liquefaction data, but it does not recover soil samples for index testing like grain size or Atterberg limits. On many Bakersfield projects we combine CPT pushes with one or two SPT borings—the borings provide samples for lab classification and the CPT fills in stratigraphic detail between them. The decision depends on your geotechnical engineer’s requirements and the building official’s review path.
What depth can your CPT rig reach in Bakersfield soils?
In Bakersfield’s typical valley sediments—interbedded sands, silts, and clays—our 20-ton truck-mounted rig routinely reaches 60 to 80 feet before encountering refusal. Cemented lenses of the Pleistocene Tulare Formation can stop the cone earlier, which is actually useful data because it confirms the presence of a dense layer that may serve as a bearing stratum.
How fast can I get CPT results after testing?
Raw digital data is available same-day; the cone records qc, fs, and u2 at 1 cm intervals and the file can be emailed before the rig leaves the site. A processed report with corrected parameters, soil behavior type classification, and liquefaction screening takes 2–3 business days depending on the number of pushes and whether dissipation tests were performed.