Missouri River Levee 575 Groin Construction

Freemont County, Iowa

Arrowhead was awarded a $734K firm fixed-price contract to provide construction of 17 earthen groin extensions along Levee 575 in Fremont County, Iowa, adjacent to the Missouri River. The project was awarded as competitive Task Order under an IDIQ MATOC with the USACE Omaha District. The project was executed on an expedited schedule and completed within 45 days. Levee 575 and the surrounding area were severely impacted during the 2011 Missouri River flooding event, resulting in levee breeches and a variety of erosion-related damage. The primary objective of the project was to construct 17, earthen levee groin extensions perpendicular to the existing levee. The groins were designed to prevent parallel-running flood waters from causing future erosion, scouring and potential levee failure.

An area two miles south of the construction zone was established as a source of borrow material to support the project. Significant effort was required to completely survey and delineate the subsurface of the designated borrow area. The initial construction of each groin required mechanical ripping of the levee face to facilitate proper compaction and bonding of the new soil. Each groin was constructed using cohesive fill that was compacted in 8-inch lifts until the desired elevation and slope was achieved. Continuous nuclear density testing was performed to ensure proper compaction requirements were met.

Seventeen groins were constructed along a 1.5-mile section of levee. The groins were approximately 20-feet tall with 8 of the groins being 250-feet long at 300-foot spacing; and, 9 groins at 150 foot long with 180 foot spacing. Each groin was constructed in accordance with 100% design specifications defining exact location, slope, and elevation. USACE QCS was utilized for all project administration, QC inspection and scheduling documentation.