Projects

Terracon and the Rock Island District of the U.S. Army Corps of Engineers (USACE) partnered to provide geotechnical exploration and in-situ/laboratory testing for reconstruction of levees in the Two Rivers Drainage District, Louisa and Des Moines Counties, Iowa. In 2008, the area was inundated by flood waters near the confluence of the Iowa, Cedar, and Mississippi Rivers. The nearby town of Oakville, Iowa, was devastated and was essentially vacated. Erosion of the floodwaters also unearthed archeological artifacts. The purpose of Terracon’s services was to evaluate the subsurface conditions to determine the stability properties of the existing temporary levees. This study will also be used to develop design criteria for the new embankment structures. Terracon built, designed, maintained, calibrated, and tested the equipment system used in this design evaluation. This specialty instrumentation for levee evaluation was developed by Terracon in the USACE Omaha District studies in the Chalmette and the Citrus Land Levee Project. The equipment includes specialty pore pressure vibrating wire transducer instrumentation to determine the seepage paths and pore pressures beneath the new levees planned and temporary levees previously constructed. The initial site exploration included mobilizing our truck-mounted CPTu unit to evaluate subsurface soils conditions to depths of about 50 feet. Terracon provided database entry and interface of all the CPTu data into the Forensic Rapid CPTu. All boring and lab testing data will be entered into gINT software. Based on the cone results, the second phase of the exploration consists of conventional borings with in-situ vane shear tests on clays layers identified by the CPT soundings. Future laboratory testing is expected to include unconsolidated, undrained triaxial tests, unconfined compression shear tests, Atterberg limits, and grain size analysis.