City of Dallas Floodway System (DFS) Case Study:100-Year Levee Remediation

The Dallas Floodway System (DFS) consists of 37 km of earthen levees, pump stations, gravity sluice gates, and pressure storm sewers along the Trinity River in Dallas, Texas. Construction of the original system was completed in the 1930s after the region experienced catastrophic flooding from the Trinity River in 1908. The DFS was strengthened in the 1950s by the U.S. Army Corps of Engineers (USACE). In 2009, the USACE, through the Levee Safety Program, rated the DFS as "Unacceptable" during Periodic Inspection No. 9. As a result of this inspection, the USACE rescinded their letter of support for accreditation from the Federal Emergency Management Agency (FEMA). The City of Dallas worked with HNTB Corporation (HNTB) and the USACE to assess the levees anddesign improvements to the levees, including over 5,700 m of seepage cutoff walls. In March of 2012, the City of Dallas awarded Magnus Pacific Corporation (Magnus Pacific) the 100-year Levee Remediation - Cutoff Wall Improvement project, a critical step toward regaining the FEMA 100-year accreditation. Magnus Pacific was the prime contractor for the project, supported by specialty subcontractors Layne Geo and SMB Enterprises, Incorporated. This paper presents a case study of the levee assessment, design, and construction of over 5,700 m of seepage cutoff wall.