Yolo County, under an agreement with the California Department of Water Resources (DWR) Small Community Flood Risk Reduction Program (SCFRRP), has prepared an initial study (IS) with proposed mitigated negative declaration (MND) in compliance with the California Environmental Quality Act (CEQA) to evaluate and address any potential consequences of the proposed Knights Landing Flood Management Project, Drainage Infrastructure Improvements element. DWR is providing funding for this project and is a CEQA responsible agency for the IS/MND.
The town of Knights Landing (Town) is an unincorporated community within Yolo County, California. In 2017, Yolo County received a grant from DWR's 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 experienced 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 the 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 included funding to complete the design, environmental documentation and permitting, and construction 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 an analysis of three alternatives to alleviate the following 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 the following four project elements:
- The design of levee improvements along the Sacramento River adjacent to town; the design and permitting of the Knights Landing Ridge Cut levee; and the design and permitting of the Mid-Valley Levee Reconstruction to include the construction of Sites 9 & 10.
- Completion of Phase 1 concepts for Portuguese Bend and Grays Bend Habitat enhancement projects;
- The design, permitting, and construction of the Drainage Infrastructure Improvements; and
- The design of the New Cross Levee and New Cross Levee Loop Trail.
The third element listed above is the element subject to this staff report.
When the Knights Landing Flood Management Project is completed it will reduce or prevent flooding to a population of 995, approximately 321 structures, and 3,500 acres of prime agricultural lands.
Yolo County, in cooperation with DWR, is proposing to construct drainage facility improvements within the town of Knights Landing. 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. A figure showing Project Features is included as Attachment A.
Potential geotechnical investigations and any utility relocations would occur within the designated project area. Tree and/or vegetation removal is expected to be necessary in the immediate area around the existing arch culvert just north of the intersection of County Road 116 and Railroad Street to accommodate construction associated with removal of the concrete arch culvert and construction of the new earthen channel through the railroad embankment.
The County has principal responsibility for carrying out the Project and is, therefore, the CEQA lead agency for the IS/MND. The County has an agreement with DWR for Project funding; therefore, DWR is a responsible agency pursuant to CEQA. The County prepared the IS/MND to evaluate the expected environmental effects of the entire Project, and has incorporated mitigation measures to reduce or eliminate any potentially significant project-related impacts.
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 March 15, 2022, through April 14, 2022. A total of four comments were received during the review period from three commenters: the Yocha Dehe Wintun Nation, the Central Valley Regional Water Quality Control Board, and the United Auburn Indian Community (two comments received). The comment letters, as well as corresponding responses from the County, can be found in Appendix G of the attached Final lS/MN (Attachment B).
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 project would have no impacts on aesthetics; agriculture and forest resources; energy; land use and planning; mineral resources; population and housing; public services; recreation; transportation; and wildfire.
The project would have a less than significant impact on air quality; geology and soils; greenhouse gas emissions; hazards and hazardous materials; hydrology and water quality; noise; and utilities and service systems.
The project would have less than significant impact with mitigation on biological resources; cultural resources; and tribal cultural resources. The Mitigation Monitoring and Reporting Program can be found in Appendix F of the Final IS/MND.
Upon adoption of the IS/MND and approval of the project, staff from the County Administrator's Office will file a Notice of Determination with the County Clerk-Recorder and the State Clearinghouse in compliance with Section 21152 of the Public Resources Code (Attachment C).