FINAL PUBLIC NOTICE

SACRAMENTO RIVER WEST BANK SEEPAGE MITIGATION PROJECT (PHASE 2)

SACRAMENTO RIVER WEST SIDE LEVEE DISTRICT

The U.S. Department of Homeland Security’s Federal Emergency Management Agency (FEMA) proposes to provide federal financial assistance under the Hazard Mitigation Grant Program to the Sacramento River West Side Levee District (SRWSLD) (Subapplicant) in Yolo County, California, to construct approximately 4500 feet of permanent seepage berm along the landside toe of the Sacramento River West Levee. The project seeks to reduce the threat of levee failure.  Fortification of the SRWSLD levees along the Sacramento River serves to protect life and property in the county.  Pursuant to Executive Order 11988 (Floodplain Management), Executive Order 11990 (Protection of Wetlands), and FEMA’s implementing regulations at Title 44 Code of Federal Regulations Part 9, FEMA hereby provides interested parties with a notice of its final decision and an explanation of the alternatives considered.

Berm construction will begin with the installation of stormwater pollution prevention measures. An irrigation pipe, which runs parallel to the levee, will be relocated to the footprint of the proposed seepage berm. Clearing and grubbing will be completed on the landside slopes of the levee and adjacent land within the berm footing. Following clearing and grubbing, the first 24-36 inches of material will be removed and stockpiled along the toe to provide a level working surface for the berm. A 12-inch-thick layer of sand, topped by a 12-inch-thick layer of drain rock, will be placed over geotextile fabric on the levee slope and down past the toe of the levee. The extent of the drained berm will range from two-thirds of the levee height on the slope to past the toe up to 80 feet, depending on the seepage conditions at each location. A perforated pipe will be placed at the toe of the berm to discharge drainage into a new ditch at the toe of the berm.  Construction will include approximately 43,000 cubic yards of excavation and placement of 43,000 cubic yards of imported fill. The drain layer within the seepage berm will include placement of approximately 33,000 tons of sand and 26,500 tons of drain rock.

The project area is depicted on FEMA Flood Insurance Rate Map (FIRM) Panel 06113C0305G, effective date June 18, 2010. The FIRM shows that the Proposed Action is within Flood Zone A.  The U.S. Fish and Wildlife Service National Wetlands Inventory map shows Riverine and Freshwater Forested/Shrub Wetland in the project area.

A map of the project area and its location within the floodplain and wetlands is available for public review. Parties interested in reviewing a copy of the map should contact the FEMA Region 9 Environmental Officer using contact information provided in this notice.

Two alternatives to the Proposed Action were considered: the No Action Alternative and the Cutoff Wall alternative. Under the No Action Alternative, no activity would occur to address the seepage issue. The no-action alternative was not selected as it places a larger geographical area at significant risk of deep flooding. The project site has repeatedly been impacted by levee seepage and the condition will not improve without implementing a seepage mitigation project. The Cutoff Wall alternative is also located in the floodplain and would involve constructing a 85-100 foot deep wall through the center of the levee using a soil/bentonite slurry. This wall would create an impermeable barrier and would reduce/eliminate seepage through and under the levee. This alternative would cost approximately $26,000,000 to construct while the proposed action would cost $4,888,148. This alternative was not selected as it requires a significantly greater construction effort with greater potential impacts to wetlands and biological resources and requires much more time to implement. 

FEMA has determined that the Proposed Action is the only practicable alternative available; therefore, the Proposed Action must occur within the floodplain. The Proposed Action would not have a significant adverse impact on the floodplain or wetlands and would benefit the area by reducing the risk of flooding and overwhelming infrastructure.

Additional information about the Proposed Action may be requested by writing to the FEMA Region 9 Environmental Officer at FEMA, 1111 Broadway, Suite 1200, Oakland, California 94607, or FEMA-R9-EHP@FEMA.DHS.GOV. All requests should be received no later than 15 days after publication of this notice. No action will be taken before this date.

 

The Sacramento River West Side Levee District (SRWSLD), acting as the California Environmental Quality Act (CEQA) lead agency and project proponent, has reviewed the proposed project described below to determine whether substantial evidence supports a finding that project implementation could have a significant effect on the environment. “Significant effect on the environment” means a substantial, or potentially substantial, adverse change in any of the physical conditions within the area affected by the project, including land use, air, water, minerals, flora, fauna, ambient noise, and objects of historic or aesthetic significance.

Name of Project: Sacramento River West Bank Seepage Mitigation Project, Levee Miles 3.41 to 6.45

Project Location: The proposed project is located along the landside toe of the Sacramento River west levee between levee miles 3.41 and 6.45, approximately 3 miles north of the community of Knights Landing in Yolo County, California. The right (west) bank of the Sacramento River in the project area is a Sacramento River Flood Control Project (SRFCP) levee. The entirety of the project area is on the landside of the levee.

Project Description: SRWSLD is proposing the Sacramento River West Bank Seepage Mitigation Project, Levee Miles 3.41 to 6.45 (proposed project) to construct approximately 3.25 miles of permanent drained seepage berm over several construction seasons along the landside toe of the Sacramento River west levee. The proposed project would be constructed in response to seepage that occurs periodically along the levee toe during high water events in the Sacramento River, as well as to prevent future seepage problems along the levee. The seepage berm would provide additional weight needed at locations where seepage has historically been observed. The additional weight and internal rock drainage layer would help to counteract and contain upward seepage forces from under-seepage during high water events.

If left unaddressed, seepage can lead to erosion of the landside levee toe and possibly levee failure. Drained seepage berms are landside earthen embankment structures that resist accumulated water pressure and safely release seeping water at the landside toe of the berm through an internal rock drainage layer.

The first 1.3 miles of berm would be constructed in 2018, with additional sections being constructed over the next 5-7 years as additional funding becomes available. Berm construction would occur between April 15 and November 1 in any given year, with the actual duration dependent on the length of berm to be constructed in each individual construction year. No known hazardous waste sites exist in the project area.