Lathrop, California

The Federal Emergency Management Agency (FEMA) has provided Reclamation District No. 17 (RD-17) with a Provisionally Accredited Levee (PAL) offer letter. ENGEO has been retained to provide ongoing consultation and additional analysis of the existing 19 mile long levee system within RD-17. The purpose of our services is to assist in coordination with FEMA, the Army Corps of Engineers (Corps), the Central Valley Flood Protection Board, and the Department of Water Resources (DWR) to maintain the current levee certification. In addition, we have further evaluated the potential for under seepage effects on the existing levees and provide design recommendations for remedial measures to reduce exit gradients to appropriate levels. The initial stage of work focused on maintaining the current FEMA 100-year level of flood protection. Subsequent stages of work consist of designing required levee improvements to increase the level of flood protection within RD-17, in accordance with recently implemented California requirements.

ENGEO is providing on-site testing and observation and laboratory QA/QC services during construction. Construction of the first stages of levee improvements began in the fall of 2008. The 2008 improvements consist of 65- to 85-foot-wide seepage berms underlain by a drainage blanket with a natural sand filter. Additional levee improvements, including supplemental seepage berms, subsurface seepage collection systems, and seepage cut-off walls, will be implemented during future construction seasons.

In conjunction with the geotechnical seepage mitigation design, ENGEO participated in the preparation of and Early Implementation Project (EIP) grant application package for submittal to DWR. As part of the EIP application ENGEO performed hydraulic analyses of the San Joaquin River at proposed levee set-back locations. The purpose of the hydraulic analyses was to evaluate potential detrimental hydraulic impacts to realigning portions of the existing levee system.