Consider approval of the Huff's Corner Levee Raise and Channel Reconfiguration Project and related plans and specifications for the project; adopt an Initial Study/Mitigated Negative Declaration and Mitigation Monitoring and Reporting Program, as the appropriate level of environmental review in accordance with the California Environmental Quality Act.  (No general fund impact) (Perez/Sabatini)

The section of Cache Creek known as "Huff's Corner" is a small reach on the right bank extending approximately 2,700-feet upstream from Interstate 5, north of Woodland, in unincorporated Yolo County.  The levee at Huff's Corner was initially constructed by the U.S. Army Corps of Engineers (USACE), although the precise date of construction is unknown.  Topographic maps suggest this segment of the levee was constructed by 1951, although previous site records indicate it was constructed as early as 1938.

In October 2012, Yolo County, through the Central Valley Flood Protection Board (CVFPB), initiated the process of forming a Maintenance Area for maintenance of the levee.  The Maintenance Area was not formed because the initial cost of completing the deferred maintenance required for the formation of a Maintenance Area was prohibitive to Yolo County and local landowners.  In early 2018, Yolo County initiated engineering recommendations to determine what would be required to catch up on the deferred maintenance.

In addition to the deferred maintenance, two major project improvements were identified: (1) a raise of the entire reach of the levee to restore it to the original design height; and (2) a channel reconfiguration to control erosion and remove excess sedimentation.  These components are collectively referred to as the Huff's Corner Levee Raise and Channel Reconfiguration Project.  A figure depicting both components of the project can be found attached as Attachment A.

The Project was developed by Yolo County and is funded through a cost-share grant administered by DWR through the State's Flood System Repair Program (FSRP) - Contract Number 460013693.  

There are two distinct components of this Project.  The first is the levee "raise," which is more accurately described as a restoration action to return the levee to the original design height.  The second component is the Cache Creek channel reconfiguration.  

USACE Periodic Inspection Reports identify the entire 2,700-foot reach as being freeboard deficient (i.e., below the design height).  The Project will raise the entire reach approximately 4 to 6 feet to meet the 1957 design profile, which includes 3-feet of freeboard (i.e., levee that is not under water during a particular water level to which it is designed).  To accomplish the required elevation, the design includes widening the base of the levee on the land side by approximately 12 to 15 feet, and will include a revised Operations and Maintenance Easement corridor extending an additional 15 feet beyond the new land side toe of the levee.

County Road 18 is located on the levee crown over the western 1,100-feet of the proposed levee raise.  The Project includes removal and replacement of the affected section of County Road 18.  The portion of the levee that extends northward from the hairpin turn of County Road 18 to Interstate 5 will be completely degraded down to level earth and a new levee will be built in the same location.

The right bank of Cache Creek at Huff's Corner has approximately 100 linear feet of near-vertical bank, 30 to 50 feet high, which is undercut into the levee slope.  The Project will repair this erosion site and is designed to address the root cause of the problem, namely an abrupt, near 90-degree bend of Cache Creek at the site of the worst erosion, before reaching the Interstate 5 bridge.  Significant point bar deposition has occurred on the inside edge of the bend opposite of the eroded scarp.  A vegetated island is also in the channel at this location.

The point bar and mid-channel island both have the effect of constraining the creek flow, thereby increasing erosive potential and pushing that highly erosive flow up against the eroding scarp and threatening to erode a bank stabilization project implemented by the County in 2009.  The project will address these issues with a three-pronged approach.

First, sediment will be removed and off-hauled from the left-side secondary channel.  Second, some of the vegetation currently stabilizing the mid-channel island will be removed.  Finally, a sacrificial terrace will be constructed along the right bank which will serve to reduce flow velocity against the bank and direct flow more towards the center of the channel.

The County prepared an Initial Study/Mitigated Negative Declaration (IS/MND) to evaluate the expected environmental effects of the entire Project, and has incorporated mitigation measures to reduce or eliminate any potential significant project-related impacts (Attachment B).

The IS/MND was submitted to the Yolo County Clerk-Recorder's Office and the State Clearinghouse and circulated for public review and comment from May 12, 2021, through June 10, 2021.  A total of 5 comments were received during the review period.  The comment letters, as well as corresponding responses from the County, can be found in Attachment C. None of the comments received required revisions to the IS/MND.

Staff has determined from the prepared Initial Study that the project would not have a significant effect on the environment for the following reasons:

The IS/MND was initially adopted by the Manager of Natural Resources on July 30, 2021 in anticipation of a Flood Hazard Development Permit approved at the staff level and for application of other agency permits.  A Notice of Determination was filed with the Clerk Recorder's Office on August 3, 2021 (Attachment D).  The Flood Hazard Development Permit was not approved at the time due to scheduling and workload challenges, and will be approved following the Board's approval of implementation of the project.

The Board of Supervisors' consideration of these project components requires it to adopt the IS/MND as the appropriate level of CEQA analysis. Upon approval, staff from the County Administrator's Office will file a new Notice of Determination with the County Clerk-Recorder and the State Clearinghouse in compliance with Section 21152 of the Public Resources Code (Attachment E).

Staff from the County Administrator's Office has collaborated with staff form the Department of Community Services and the Office of County Counsel, as well as the State Department of Water Resources and the Board's Cache Creek Ad Hoc Subcommittee on this item and project.

The competitive bid process will be completed in accordance with State law.  Bids will be opened and read publicly at the Department of Community Services.  A contract may only be awarded to the lowest responsive and responsible bidder.