Evaluation of Shoring Wall Failure Irving, Texas

In 2017, the City of Irving, Texas (City), developed plans to construct a new lift station along the banks of the Trinity River. A geotechnical investigation identified sandy clay soils interbedded with lenses of clean sand. Because of the depth of the lift station, the proposed design would extend below the depth of the groundwater encountered at the time of the investigation. A shoring system was required to retain both the soil and water table from the river. An internally braced sheet pile coffer dam was installed in May and June of 2018. In September of 2018, the Trinity River experienced a flood event that inundated the excavation and shoring wall system causing the failure of one side and significantly bowing the other three. Engineering Analytics, Inc. (EA) was contacted to investigate the cause of the failure. Our investigation found that the structural engineer hired to prepare the design of the shoring system had failed to use the design parameters provided by the geotechnical engineer. The structural engineer had instead interpreted field classification data from the geotechnical borings to develop his own design parameters. Ultimately, the shoring system provided was subjected to soil and water loads more than 5 times the design loads. The primary lesson learned from this case study is that all members of the design team need to use the same design parameters. Communication regarding design parameters is vital to prevent miscommunications.