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Environmental and Geotechnical Construction Services

Oil & Gas

Tank Footprint Subsurface Ground Improvement - Gulf Coast

  • Subsurface soil treatment for 14 proposed tank footprints and 4 proposed pump pads
  • Treatment of 205,000 CY using type I-II Portland Cement
  • 8 FT dia. vertical auger overlapping columns achieved at minimum UCS of 200 PSI in 28 days

As part of the capital program for this active refinery’s expansion, ENTACT performed subsurface soil treatment of soft saturated soils where a series of above-ground product storage tanks were constructed. Ground improvement measures were completed at 14 proposed tank footprints and 4 proposed pump pads in order to minimize the potential for future tank foundations and pump pads settlement. Tank diameters ranged from 78-212 feet. The specified treatment consisted of installing a series of 8-foot diameter soil-cement columns on an 11-foot by 11-foot grid (i.e. using a soil treatment replacement ratio of 41.52%) underneath the planned footprint of each tank foundation. The proposed columns were constructed from elevation +9 feet and terminated at elevation -11 feet and achieved a minimum unconfined compressive strength of 200 psi in 28 days. Additionally, a series of overlapping 8-foot diameter columns were constructed along the footprint of each future “tank foundation ring”. The proposed overlapping columns were installed in one row using a circular pattern with 7′-6″ on center spacing (i.e. 6-inch overlap between adjacent columns).

ENTACT employed (2) In-Situ Vertical Auger Mixing Rigs complete with their respective Grout Batch Plants that worked concurrently in order to accomplish the specified work within the allotted durations. ENTACT conducted a series of treatability studies at our in-house treatability laboratory to determine the optimum reagent and delivery program required to meet project objectives and performance criteria. Reagents included type I-II Portland Cement to treat a total of 205,000 cubic yards.