Meeting of the Central Valley Flood Protection Board February 28, 2020 Staff Report for Permit No. 19153 Agenda Item No. 11B Department of Water Resources Lower Elkhorn Basin Levee Setback Project, Yolo County 1.0 – ITEM Consider conditional approval of Permit No. 19153 (Attachment A) to construct the Lower Elkhorn Basin Levee Setback Project (LEBLS) in Yolo County. 2.0 - APPLICANT State of California, Department of Water Resources (DWR) 3.0 – PROJECT LOCATION The LEBLS project includes the east levee of the Yolo Bypass from I-5 to the Sacramento Bypass and the north levee of the Sacramento Bypass in the Lower Elkhorn Basin (Attachment B) in Yolo County. 4.0 – PROJECT DESCRIPTION This project will accomplish multi-benefit objectives. The primary objectives are to provide flood risk reduction for improved public safety and ecosystem benefits. These are achieved by enhancing the flood system capacity and protecting high risk communities in the Sacramento Basin through expansion of the Yolo Bypass and the Sacramento Bypass. The project will provide improved public safety for more than 780,000 people in the Lower Sacramento River Basin area by reducing flood stages for the 200-year flood event on the Sacramento River and I-5 in the vicinity of the Yolo Bypass. Application No. 19153 Agenda Item No. 11B The project will include the following flood-risk reduction elements: • Widening the Yolo Bypass by constructing a setback levee approximately 1,500 to 1,800 feet east of the Tule Canal in the Lower Elkhorn Basin between I-5 and the Sacramento Bypass; • Widening the Sacramento Bypass by constructing a setback levee approximately 1,500 feet north of the existing levee; • Degrading 80 percent of the Yolo Bypass east levee, leaving approximately 500 feet long segments for upland habitat every 2,000 feet. The existing Sacramento Bypass north levee will be degraded; • Improving the Lower Elkhorn Basin interior drainage system to facilitate discharge of precipitation volumes up to the 100-year flood event; • Implementing ecosystem improvements in the Lower Elkhorn Basin to mitigate project impacts, which will provide multiple ecosystem benefits to the surrounding areas. These ecosystem benefits include: o Adding approximately 1,100 acres of inundated floodplain habitat that is compatible with agriculture; o The establishment of a Tule Canal buffer that can provide additional riparian habitat; o Direct ecosystem connectivity to the Sacramento Bypass Wildlife Area; o Providing a substantial portion of the connectivity needed to bridge the gap between Knaggs Ranch and the Fazio Wildlife Area; o The alleviation of fish-stranding concerns and promotion of operational flexibility for agriculture and food web distribution flows; and o Promoting an operational landscape that benefits agriculture and fish rearing habitat. Several utility pipes will need to be relocated and deepened. Utility penetrations must comply with design requirements as defined by Title 23, Division 1. An existing 12-inch diameter steel pipe that delivers jet fuel to Sacramento International Airport was relocated in 2019 at least 50 feet below the Sacramento Bypass and the setback levee. AT&T will bore new fiber optic conduit approximately 20 feet below the setback levee at two locations. The existing pump station pipe outfalls will be modified and relocated. In addition, the Bryte Landfill site, north of the Sacramento Bypass, is currently being relocated. The relocation will be completed in 2020. The draft Permit No. 19153 in Appendix A includes the following project components: • Construction of the setback levees on the Yolo and Sacramento Bypasses. • Placement of discharge pipes associated with the new pump station. Page 2 of 12 Application No. 19153 Agenda Item No. 11B • Degradation of 80 percent of the Yolo Bypass east levee; • Degradation of the existing Sacramento Bypass north levee; • Implementation of ecosystem improvements in the Lower Elkhorn Basin; and • Relocation of the AT&T fiber optic lines. Parts of the project will be designed and constructed by other agencies and are either outside the Board jurisdiction or have/will apply for a separate Board encroachment permits. The Board Permit does not include the following project components: • Design and construction of improvements to the Lower Elkhorn Basin interior drainage system of ditches, culverts, a new pump station, and detention basin. This work will be completed by the Sacramento Area Flood Control Agency (SAFCA); • Reconstruction of rural county roads; • Changes to overhead PG&E electrical lines; • Relocation of the Sacramento International Airport jet fuel line; and • Relocation of the Bryte Landfill. A Board has already permitted the jet fuel line relocation effort. A “name change” Board Permit will need to be issued for the AT&T fiber optic lines. 5.0 – AUTHORITY OF THE BOARD California Water Code § 8534, 8590 – 8610.5, and 8700 – 8710 California Code of Regulations, Title 23, Division 1 (Title 23): • § 6, Need for a Permit • § 108, Existing Encroachments within an Adopted Plan of Flood Control • § 116, Borrow and Excavation Activities – Land and Channel • § 120, Levees • § 121, Erosion Control • § 123, Pipelines, Conduits and Utility Lines • § 124, Abandoned Pipelines and Conduits • § 130, Patrol Roads and Access Ramps • § 131, Vegetation Page 3 of 12 Application No. 19153 Agenda Item No. 11B • Rivers and Harbors Act of 1899, Title 33 United States Code, § 408, hereinafter referred to as Section 408 6.0 - PROJECT ANALYSIS 6.1 – Project Background Early in the twentieth century, United States Geological Survey recognized that the capacity of the Sacramento River channel was not adequate to convey river flood flows. As a result, levee construction along the Yolo Bypass began in 1917. The levees along the Yolo Bypass were constructed using a clamshell bucket dredger, loosely depositing high-plasticity clays with organics as the main embankment material. The clam shell excavation created what is known as the Tule Canal at the waterside toe. Available information indicates the foundation soils include soft to stiff clays with slickensides and some organic lenses from basin deposits. The project site, located in the Lower Elkhorn Basin, is primarily used for agricultural production of row crops such as tomatoes, sunflowers and safflowers; alfalfa; and nut- bearing orchards. The population is fewer than 100 people with fewer than 100 structures including farm buildings, permanent and temporary residences, and commercial buildings. The Basin is subdivided by interior drainage canals forming three sub-basins identified as Reclamation Districts (RD): RD 537 in the southeast quarter of the Basin, RD 785 in the southwest quarter of the Basin, and RD 827 in the northern part of Basin. The RDs each operate their own interior drainage canals and pump systems for crop irrigation and interior drainage. The topography of the Lower Elkhorn Basin area is relatively flat and slopes gently from northeast to southwest. The ground surface elevations range from about 10 to 25 feet North American Datum of 1983 (NAD83). The Yolo Bypass is oriented generally north to south. The Sacramento Bypass channel is oriented east to west. 6.1.1 – Project Alteration Need The project is needed for the following reasons: • A high risk of flooding threatening life and public safety, property, critical infrastructure, and the environment exists throughout the areas protected by the Yolo and Sacramento Bypasses, including, but not limited to, portions of the cities of Sacramento, West Sacramento, and Woodland. • The project will provide increased system resiliency to convey large flood events as outlined in the 2017 Central Valley Flood Protection Plan Update for the Yolo Page 4 of 12 Application No. 19153 Agenda Item No. 11B Bypass upstream of I-5 in the City of Woodland and the Sacramento River in the City of Sacramento. • The project will address deficiencies in the existing Sacramento Bypass North Levee and portions of the Yolo Bypass East Levee, as evidenced by several slope failures, sloughing, and slope cracking that occurred in 2017 and 2019. • Long-term operation, maintenance, repair, replacement, and rehabilitation costs for the existing flood management facilities will continue to increase as these facilities age. • Climate change is expected to increase hydrologic variability, put further stress on the flood management system and erode the current level of flood protection. • Impaired hydrologic and geomorphic processes; eliminated, fragmented, and degraded habitat; and other stressors have reduced the abundance, distribution, and diversity of native aquatic and terrestrial species in the Sacramento Basin. • The project will improve native fish and riparian habitats that have been reduced in the Sacramento River Basin. 6.2 – Hydraulic Analysis DWR conducted Hydrologic and Hydraulic (H&H) system performance and risk and uncertainty analyses to comply with Section 408 Engineering Circular 1165-2-216, and to determine H&H impacts within the overall Sacramento River Flood Control Project (SRFCP). The H&H analysis informs the levee design for setting levee height and identifying potential erosion impacts associated with the project. The design water surface elevation (DWSE) for the project is the 100-year water surface elevation. The levee heights were determined by the 100-year DWSE plus 6 feet of freeboard, plus one additional foot for potential future climate change adaptation/resiliency. Many different model results were