Natomas Levee Evaluation Program
A series of levees along the Natomas Basin help protect the Sacramento area from floods, but the levee system was judged to be at risk of both 100- and 200-year flood levels by the Sacramento Area Flood Control Agency. In response, HDR provided design services for necessary repairs to levees on the lower Sacramento River and the American River. HDR focused on designing a project based on an aggressive schedule and that would be FEMA-certified. HDR design services, plans, specifications and cost estimates included the 30-, 60-, 90- and 100-percent levels.
The HDR design team included experts in geotechnical, environmental, permitting, real estate, hydrology & hydraulics and construction services. A detailed alternatives analysis helped understand seepage conditions below the levees to develop the most effective combination and configuration of seepage control measures. To mitigate the potential for further underseepage (including the potential for sand oils, material piping and slope instability), alternatives considered included a deep seepage cutoff with conventional slurry methods or deep soil mixing techniques. A quality control program included the U.S. Army Corps of Engineers throughout the design process to ensure a project that the Corps could certify to FEMA at the conclusion of construction.
Outstanding Flood Management Project, American Society of Civil Engineers, Region 9