MARYSVILLE, Calif. --Two giant, ultra-modern geotechnical construction rigs work side by side here, implanting a deep-soil-mixed cutoff wall backbone into a section of the Marysville Ring Levee near the town’s high school, as crews begin extended shifts to meet essential weather and endangered species deadlines.
Contractors on this U.S. Army Corps of Engineers project face a Sept. 30 deadline for completing this particular 2,200-foot section in order to stay on schedule and avoid negatively affecting protected wildlife adjacent to the levee, so the second specialized rig was added next to the original unit in early September and the daily work schedule is now 6 a.m. to 9 p.m.
Contractors sent out notice of the extended work schedule Friday, Sept. 7, to homes along this stretch of the levee. Crews will also work two Sundays – Sept. 15 and 22. Work schedules will revert to 12-hour days (6 a.m. – 6 p.m.) and six days per week after Oct. 1.
This construction continues the first part of the four-phase, $100 million project to decrease flood risk for Marysville by 2016. In order to help this historically flood-prone Northern California town between the Feather and Yuba rivers, the Marysville Ring Levee Project includes installation of five miles of seepage cutoff walls into the seven-mile levee surrounding the town.
Deep-soil-mixed cutoff walls create a vertical barrier to seepage through or under existing earthen levees. This cutoff wall is made of a controlled mixture of native soil, cement and bentonite clay.
Each of the two big rigs installing the cutoff wall has three augers, or drill bits, and can dig down more than 120 feet. The ratio of soil, cement and bentonite pumped down into the cut is remotely controlled from a high-tech batch station a few hundred yards away from the drilling rigs.
The Corps awarded a $10.8 million contract to Raito Inc. of San Leandro, in August 2010, using American Recovery and Reinvestment Act funding, to complete Phase 1 of the Marysville project, which is a partnership between the state’s Central Valley Flood Protection Board, the Marysville Levee District and the Corps.
The Marysville project began in 2010 with widening of the levee. In 2011, test sections were installed and then actual cutoff wall construction followed until work was stopped Aug. 18. When the government reviewed the test section in July 2011, concerns arose over homogeneity of mix materials and continuity of cutoff wall panels.
“Because the contractor was allowed a variance in the methodology for cutoff wall installation, the government felt additional testing was necessary in order to assure contract requirements were met,” said Erik James, lead geotechnical engineer with the U.S. Army Corps of Engineers Sacramento District. “The contractor, local and state sponsors and the Corps negotiated a modification of testing methods to provide that assurance.”
Construction resumed in June 2012 and the current schedule allows for completion of this reach prior to the beginning of flood season on Nov. 1. The second phase of the Marysville project is slated to begin in 2013.
“I’m satisfied with this year’s work,” said James. “The folks in Marysville seem genuinely grateful for the work we’re doing and they understand the importance to their town.”
The U.S. Army Corps of Engineers Sacramento District provides planning, engineering, project management, environmental restoration and construction services to civilian and military customers in parts of eight western states, including California, Nevada, Utah, Arizona, Colorado, Idaho, Oregon and Wyoming.