Natomas Levee Improvement Project

MBK has provided Project and Program Management, as well as H&H support for this project from the fall of 2006 to the present. This project involves all of the levees surrounding Natomas and provides for the improvements to first gain 100-year protection; then, eventually 200-year protection. The program is expected to cost in excess of $400 million, with construction projects starting in 2007 and proceeding through 2013. The program is expected to bring Natomas out of the 100-year floodplain in 2010. The program involves numerous consulting firms and includes coordination between geotechnical investigations, mitigation alternatives for levee improvements, and environmental enhancement. Coordination is being maintained with Corps of Engineers, the State of California, and other agencies and involved groups. In both the study and the subsequent alternatives analysis and design, explorations and lab analysis were obtained and geotechnical study was accomplished. Alternative analysis included the consideration of cutoff walls that may vary from 70 to 110 feet deep. These walls could be SCB slurry wall; SB Slurry Walls or Deep Soil Mix type of walls. Subjects such as “Chainsaw” or Jet Grouting are being studied for use in the program. Also being considered is the use of Seepage Berms or Stability Berms as well as Combined Seepage/Stability Berms. Relief Wells are also being investigated as a possible approach for remediation of the problem. As with the Study, the alternatives being studied in design also includes the potential for levee setback or partial setback for various lengths. An environmental corridor for the enhancement of the giant garter snake that could be integrated into a seepage berm concept is being looked at to provide for a win- win concept for multiple parties of interest in the area. Utilities, construction phasing, permitting, funding limitations, additional environmental considerations and moving toward a project that can be most reasonably found advantageous and acceptable to the entire array of agencies and residents is the focus of the program.

Location: Sacramento, CA

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