Adopt plans and specifications for the construction of the Knights Landing Flood Management Project, Drainage Infrastructure Improvement Project of the Phase 2 Small Community Flood Risk Reduction Program in the Town of Knights Landing. (No general fund impact) (Echiburu/Sabatini)

PROJECT HISTORY
The town of Knights Landing (Town) is an unincorporated community in Yolo County.  In 2017, the County received a grant from the State of California Department of Water Resources (DWR), Small Community Flood Risk Reduction Program (SCFRRP) to complete a feasibility study of structural and non-structural actions that could reduce flood risk to Knights Landing.  

During the winter of 2017-2018, the Town experience flooding along 2nd Street and Railroad Street that partially inundated the U.S. Post Office on 2nd Street near the intersection of Mill Street.  At the time of flooding, the Sacramento River was elevated and seepage through (or under) the levees may have been contributing to the flooding.  This seepage is accruing from the State Plan of Flood Control Levee.  This accumulation and migration of floodwater across the surfaces of the Town is influenced by direct rainfall over the Town, seepage through the surrounding levees, where elevated water from the river flows through or under the levees;  and upwelling groundwater levels due to high groundwater conditions in the basin. 

The Town drains primarily to a single ditch along the north side of County Road 116, through agricultural land sloping generally to the southeast.  An existing abandoned railroad embankment (spur alignment) is located parallel to, and east of, Railroad Street and forms a barrier to overland runoff exiting the Town to the southeast.  This forces all runoff coming from the west to collect along Railroad Street until it can flow beneath the abandoned railroad via an existing culvert.  The downstream interior watershed areas are part of a basin protected by levees on all sides that outfall to the Ridge Cut Canal.  The northern portion of this interior basis, including the Town, drains to an existing pump station located approximately two miles southeast of the Town.

The County prepared the 2019 Knights Landing Small Community Flood Risk Reduction Feasibility Study, and also commissioned a drainage study.  In 2020, the County received additional grant funding from DWR as a part of Phase 2 of the SCFRRP, which including funding to complete the design, environmental documentation and permitting, and construct the Drainage Infrastructure Improvements identified in the town of Knights Landing.

In February 2021, the Yolo County Drainage Study Report: Knights Landing was prepared, which provided analysis of three alternatives to alleviate the flooding conditions within the Town at the U.S. Post Office.  After reviewing the analysis provided in the drainage study report, the County selected Alternative 2 as the preferred alternative for the drainage facility improvements within Knights Landing.

The Knights Landing Flood Management Project currently funded under the SCFRRP Phase 2 agreement includes four project elements.  The element subject to this staff report is for the design, permitting, and construction of Drainage Infrastructure Improvements.

PROJECT DESCRIPTION
The purpose of the project is to improve drainage facilities to reduce flooding within the Town.  The project would incorporate roadside ditch improvements along 2nd Street between the Post Office and Railroad Street to improve storm water drainage capacity; a buried closed conduit under Railroad Street between 2nd Street and 4th Street (approximately 2.25-foot-wide by 1-foot-deep); an open channel along the east side of Railroad Street between 4th Street and 7th Street (approximately 3-foot-deep, 2:1 side slopes); removal of the existing concrete arch culvert; and degrade of the abandoned railroad embankment using a 50-foot-wide open cut channel.  The project construction cost is estimated at $350,000.

A request for authorization to proceed with construction was submitted to DWR in March 2022.  The project is programmed for DWR reimbursement for up to 90% of the final cost, with the County's contribution of construction funds, the County will not need to request the full amount programmed.  Staff has been informed that the reimbursement could be distributed no later than June 1, 2023.  County staff recommends proceeding with the project in order to preserve State funding.

The project will take approximately three weeks to complete.  Work is expected to be completed by October 2022.

ENVIRONMENTAL REVIEW
An Initial Study/Mitigated Negative Declaration and Mitigation and Monitoring and Reporting Plan was adopted by the Board of Supervisors on May 10, 2022 (Minute Order No. 22-57; Item No. 11).  A Notice of Determination was filed with the County Clerk-Recorder and the State Clearinghouse in compliance with Section 21152 of the Public Resources Code on May 12, 2022 (Document No. 57-05122022-054).  A State Clearinghouse Number of 2022030394 was attributed to this project.

CURRENT REQUEST
At this time, Staff is requesting Board adoption of the Plans and Specifications for the project, as well as Board authorization for Staff to go out to bid for the work and sign all associated contracts and change orders.

The County has been collaborating with the State Department of Water Resources and the Yocha Dehe Wintun Nation on this project.