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Title:	Cache Creek North Levee Setback Project, Critical Erosion Site LM 3.9L and LM 4.2L : Final Environmental Assessment
Authors:	United States. Army. Corps of Engineers. Sacramento District
Keywords:	Cache Creek (Lake County and Yolo County; Calif.) Levees Erosion Flood control Environmental protection Environmental management
Publisher:	United States. Army. Corps of Engineers. Sacramento District.
Abstract:	The California Department of Water Resources (DWR) Flood System Sustainability Branch repairs significant levee damage due to erosion, seepage, and/or stability deficiencies. Damaged levee sections are identified during levee inspections throughout the Sacramento and San Joaquin River Flood Control System. DWR proposes to address critical erosion damage on the left bank of Cache Creek at Levee Miles (LM) 3.9 and LM 4.2 in Yolo County that threatens the stability of the existing levee. The DWR Cache Creek North Levee Setback Project – Critical Erosion Site LM 3.9L and LM 4.2L (proposed project) proposes to construct setback levees at each erosion site along the north bank of Cache Creek. Encroachment by Cache Creek into the minimum berm specification of 30 feet has been observed and identified as requiring immediate remediation to prevent levee failure at both of these sites. The levee is maintained by DWR Flood Maintenance Office, under provisions of the State Water Code Section 8361. The levee setback at LM 3.9L will be approximately 1,285 feet in length, and will be placed approximately 180 feet from the existing levee. The levee setback at LM 4.2L will be approximately 717 feet in length, and will be placed approximately 75 feet from the existing levee. The setting back of the existing levee required the acquisition of lands. In 2009, the State procured the necessary lands to implement the project. The Cache Creek levees proposed to be repaired are part of the Sacramento River Flood Control Project (SRFCP); a system of over 1,000 miles of levees, bypasses, weirs, and waterways designed to reduce flood damages in Sacramento and the Central Valley. The need for the proposed action is to maintain the integrity of the SRFCP. The Cache Creek erosion sites are at risk of an erosional failure during flooding and/or normal flow conditions. These sites must be repaired before their erosion condition becomes so critical as to require emergency repair, or they experience a levee break, resulting in losses of life and property. The proposed repair will restore the structural integrity to the existing level of flood protection of the Cache Creek north levee. The existing levee system has a design flow capacity of 30,000 cubic feet per second (cfs) which corresponds to approximately 10 year level of flood protection. The proposed action will ensure that this level of flood protection is maintained. The setback levee designs include cutoff trenches that will penetrate underlying sand layers to reduce through and under seepage. The SRFCP protects low-lying areas of the Sacramento Valley and the Sacramento–San Joaquin Delta from damaging floods. These areas contain large urban populations and industrial-commercial developments as well as extensive agriculture operations. A large amount of infrastructure, including highways, railroads, airports, water systems, and gas wells, is also present. Failure of a project levee would threaten these populations and developments.
Description:	Environmental Assessment and Finding of No Significant Impact
Rights:	Approved for Public Release; Distribution is Unlimited
URI:	https://hdl.handle.net/11681/40522
Appears in Collections:	Environmental Documents