SCH Number 2021050214

Project Info

Title

Huff's Corner Levee Raise and Channel Reconfiguration Project

Description

The Project was developed by Yolo County and is funded through a cost-share grant administered by the CA Department of Water Resources via their Flood System Repair Program (FSRP) – Contract Number 460013693. While the majority of costs to design and construct the Project are funded by FSRP, Yolo County provides a significant share of costs in the form of direct expenditures and in-kind services with multiple Yolo County Staff. 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. Both components are fully analyzed and discussed in greater detail in this IS/MND. *Levee Restoration 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 4.0 to 6.0 feet to meet the 1957 design profile, which includes 3-feet of freeboard (levee that is not under water during a particular water level to which it is designed). 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. To accomplish this 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 & Maintenance (O&M) Easement corridor extending an additional 15 feet beyond the new land side toe of the levee. Furthermore, the portion of the levee that extends northward from the hairpin turn of County Road 18 to I-5 will be completely degraded down to level earth and a new levee will be built in the same location. *Channel Reconfiguration 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 I-5 bridge. Significant point bar deposition has occurred on the inside edge of the bend opposite 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 river 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 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. *Project Details Both components of this Project will be constructed concurrently in 2022. The Project may also initiate some pre-construction activities such as tree removal, vegetation removal, general site preparation, and utility relocations in advance of major construction with proper approvals and permissions in place.

6 documents in project