Approve the plans and technical provisions for the Huff's Corner In-Channel Repair Project; authorize the Director of General Services to award a contract for construction services to Martin Brothers Construction; approve the construction contract with Martin Brothers Construction in the amount of $359,656; authorize the Director of Community Services to approve change orders consistent with applicable limits of the Public Contract Code up to a cumulative total of 10% of the contract's value; and authorize a construction contingency budget for the entire Project for 10% of the total contract's value. (No general fund impact) (Lindbo/Sabatini)

Staff is recommending that the Board of Supervisors award and approve a construction contract with Martin Brothers Construction for the Huff's Corner In-Channel Repair Project ("Project").  The Project is a component of the Huff's Corner Levee Raise & Channel Reconfiguration Phase II Project, which is funded by a Funding Agreement between the California Department of Water Resources ("DWR") and the County.

The purpose of the Project is to repair an in-channel reconfiguration project that was constructed in Lower Cache Creek adjacent to the Huff's Corner Levee in late 2022, and subsequently damaged by ensuing winter creek flows.  The Project will do this by the following actions: excavation of deposited creek gravels from the left (north) side of the channel; filling of the gravels into eroded areas on the right (south) side of the channel where the original terrace was built in 2022; and stabilization of the new fill with the installation of additional rock, erosional control fabric, soil, and revegetation.

The Project's plans and technical provisions have been included in this staff report as Attachment A and Attachment B, respectively. The subject construction agreement with Martin Brothers Construction has been included as Attachment C.

Background
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. The levee was initially constructed by the U.S. Army Corps of Engineers in 1960, and Yolo County has been the local maintaining agency since its construction.  Only the eastern 1,500 feet of this levee is within the State Plan of Flood Control.  

In October 2012, Yolo County, through the Central Valley Flood Protection Board, initiated the process of forming a Maintenance Area for the 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 the County and local landowners. 

In early 2018, the County sought engineering recommendations to determine what would be required to complete the deferred maintenance to restart the Maintenance Area formation process. 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 its original design height, and (2) implementation of a "reconfiguration" project within the Lower Cache Creek channel to control erosional forces against the levee and remove excess sedimentation. These two improvements were combined to create the Huff's Corner Levee Raise & Channel Reconfiguration Project.  However, a portion of the levee raise was determined to be unnecessary based upon further information from the US Army Corps of Engineers, the Central Valley Flood Protection Board, and DWR confirming that there had not been a prior levee constructed on an approximate 0.4-mile section of the levee.

In August 2019, the County and DWR entered into a Project Agreement to complete the design, environmental permitting, and construction of the overall project.  Utilizing funds provided by this agreement, as well as local funding contributions from the Cache Creek Resources Management Plan fund, the County was able to develop 100% designs for both project components, secure all necessary permits and environmental clearances, and complete the in-channel reconfiguration project component. Because of unforeseen Project costs and change in the scope for the levee raise component of the Project, County efforts have been focused first on the in channel reconfiguration project component.

The in-channel reconfiguration component of the project was completed in late December 2022. This project involved the removal of an in-channel sediment island adjacent to the levee that had been accumulating in the creek for decades, and the construction of a sacrificial terrace along the right bank of the creek.  Shortly after construction concluded, a series of early 2023 storms brought significant flows through the channel.  Because the recently disturbed soils had not been fully stabilized by the seeded vegetation, approximately 285 linear feet of the newly built terrace was eroded away by the creek flows. 

The County issued a formal solicitation (reference no. GSDIFBKK2413) on May 15, 2024, seeking a contractor to provide construction services. A mandatory job walk was held on May 23, 2024, and 13 vendors attended. A total of 6 vendors timely submitted bids, which were opened on June 20, 2024.  A summary of the bids received can be found below: