Project Highlights

S&ME, Inc. is the geotechnical design firm for Santee Cooper’s two new coal-fired electric generators (Units 3 and 4) at their Cross Generating Station in Pineville, South Carolina. S&ME also performed foundation testing for the $675 million Unit 3. Each new unit contains several major structures, including the turbine buildings, steam generator support structures, particulate removal structures and flue gas desulfurization structures. The new construction also includes cooling towers, a solid waste handling facility, relocated warehouse facility, a conveyor, a fuel oil storage tank and a relocated rail car repair shop. The existing Units 1 and 2 are constructed on reinforced concrete mats supported by drilled shafts socketed into the Santee Limestone. Santee Cooper and their designer/structural engineer, Parsons Energy & Chemicals Group, proposed to use a similar approach for Units 3 and 4. S&ME’s role in the project was to characterize the subsurface conditions and provide geotechnical/foundation design and construction recommendations for drilled shafts for Units 3 and 4. After the exploration began, we expanded our role to include evaluation of more innovative and economical deep foundation systems. S&ME performed the following tasks:

• Reviewed available geotechnical data for the Cross Generating Station site
• Planned, coordinated and performed an extensive field exploration
• Provided full-time engineering supervision of all field exploration and testing
• Planned and performed laboratory testing program for soil and rock samples
• Evaluated the field/laboratory test data to characterize the geotechnical conditions at the project site
• Performed a site-specific seismic study to develop alternative earthquake design information
• Provided geotechnical design recommendations, including: 1) axial and lateral capacities of drilled shaft and driven pile foundations, 2) lateral earth pressures for the design of below-grade/retaining walls, 3) allowable bearing capacities, elevations, etc. for the shallow supported structures, 4) suitability of on-site soils for reuse as structural fill, and 5) pavement thicknesses/allowable traffic volumes
• Provided recommendations for site preparation, controlled fill, and foundation construction
• Performed engineering observation and pile testing during construction of Unit 3

S&ME’s application of advanced technology such as cone penetration testing and multi-node resistivity testing, to this site resulted in a representative and accurate subsurface profile showing little or no evidence of karst features on which to base the foundation design. This, along with the results of our site specific seismic response analysis, indicated that driven pile foundations were a viable alternative to the originally planned drilled shaft foundation system. When compared to the estimated cost of a drilled shaft foundation system, the driven pile foundation system for Unit 3 resulted in a projected cost savings to the owner on the order of $7 million.