Savannah’s subsurface doesn't hide its secrets easily. The upper 30 to 50 feet are dominated by Pleistocene and Holocene deposits—interbedded loose sands, soft to medium clays, and occasional organics that shift behavior with the tide and the seasons. A standard boring with SPT sampling gives you a data point every 2.5 or 5 feet; CPT soundings give you a near-continuous profile of tip resistance, sleeve friction, and pore pressure, which makes a real difference when you’re trying to separate a thin silt seam from a true clay layer. We run our cone rigs in Savannah’s historic districts, port-adjacent industrial lots, and new residential subdivisions, always with an eye on the shallow groundwater that sits barely 4 to 8 feet below grade across much of Chatham County. Where the stratigraphy is complex, we often pair the cone data with a few targeted SPT borings to calibrate soil behavior types and confirm the Robertson chart classifications on samples we can see and touch.
A single CPT sounding in Savannah’s coastal deposits can replace four to six SPT borings for stratigraphic profiling—and it does it in half a day instead of two.
Method and coverage
Regional considerations
We worked on a five-story mixed-use project on a reclaimed site near the Savannah River where the geophysical survey had missed an infilled tidal creek running diagonally across the lot. The initial SPT borings, spaced at 60-foot centers, showed N-values in the 15–25 range—acceptable for shallow footings. The CPT profile told a different story: a 12-foot-thick lens of soft, normally consolidated silty clay with tip resistances below 0.3 MPa and excess pore pressure generation that spiked on every push. That lens was a consolidation time bomb. If the structural engineer had proceeded with the original foundation design, differential settlement would have cracked the slab within two years. We ran five additional CPT soundings on a 20-foot grid, mapped the paleochannel boundary, and the design team switched to a ground improvement strategy with rigid inclusions that bridged the soft zone. In Savannah, where relic channels and buried marsh deposits hide beneath clean-looking sand, skipping the cone data is a bet you don’t want to take.
Standards that apply
ASTM D5778-21 – Standard Test Method for Electronic Friction Cone and Piezocone Penetration Testing of Soils, IBC 2024 Chapter 18 – Soils and Foundations, including liquefaction evaluation requirements, ASCE 7-22 – Minimum Design Loads and Associated Criteria for Buildings and Other Structures, Robertson (2016) CPT Soil Behavior Type classification system, NCEER/NSF (Youd & Idriss 2001) liquefaction triggering procedures for SPT and CPT data
Complementary services
Piezocone (CPTu) Soundings
Standard cone with pore pressure measurement at the shoulder. We use 15 cm² and 10 cm² cones depending on soil stiffness and depth requirements.
Pore Pressure Dissipation Testing
Stopped-cone tests to record u2 decay over time. We provide t50 and full decay curves for consolidation rate estimation in compressible clays.
Seismic CPT (SCPT)
Downhole shear wave velocity measurement integrated with cone data. Direct Vs profiles for site class determination per ASCE 7-22.
Soil Behavior Type Profiling & Reporting
Complete digital logs with Robertson SBT classification, equivalent SPT N60 estimates, and interpreted geotechnical units ready for foundation design.
Typical parameters
Q&A
How much does a CPT sounding cost in Savannah?
For standard CPTu soundings in the Savannah area, budgets typically range from US$180 to US$250 per meter of penetration, depending on total depth, site access, and whether seismic or dissipation testing is included. We provide a fixed-price proposal after reviewing your site location and project requirements.
What depth can you reach with the CPT rig in coastal Georgia soils?
Our 20-ton truck-mounted rig routinely reaches 100 to 130 feet in the sands and clays common to Chatham County. When we encounter the dense, pre-consolidated sands of the deeper Hawthorn Formation, refusal may occur earlier—we monitor sleeve friction and tip resistance continuously and stop when capacity limits are reached to protect the cone and rods.
Can CPT data be used for liquefaction analysis under IBC?
Yes. IBC Chapter 18 and ASCE 7-22 accept CPT-based liquefaction triggering procedures. We process the cone data through the NCEER/NSF framework (Youd & Idriss 2001, updated by Idriss & Boulanger 2008), using normalized tip resistance and soil behavior type directly to compute factor of safety against liquefaction at each depth increment.
Do CPT results replace the need for soil borings and lab testing?
CPT provides continuous stratigraphic information that no boring can match, but it does not recover physical samples. For projects in Savannah requiring Atterberg limits, grain size distribution, or strength testing, we recommend a combined program: CPT for profiling and liquefaction assessment, supported by a smaller number of targeted SPT borings or thin-wall Shelby tube samples for laboratory confirmation.