2020-12-28-minutes-public-works-study-session

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Following review of the guidance document, state initiated a task order with Jacobs producing a proposal to WADOE, USACE and the Federal Aviation Administration. The Board will also recall that PW is currently engaged in an avulsion study at Hansen Pits that is being funded by the Yakima Basin Integrated Pian Habitat Subcommittee. That work is being conducted by Watershed Science and Engineering (WSE). Recently, staff evaluated preliminary avulsion study results with WSE. DISCUSSION: The proposal memorandum is attached as EXHIBIT 1 for Board review. WADOE's response (electronic mail) is attached as EXHIBIT 2. PW anticipates a favorable response from all resource agencies. The current avulsion study of the Yakima river at Hansen Pits results from a commitment made by the Board to the Habitat Subcommittee in consideration of their support acquiring MFARM (EXHIBIT 3). The acquisition of MFARM in 2019 and the pending acquisition of FLYING M create unique and real opportunities for enviromnental mitigation work on the main stem Yakima River. Knowing that onsite mitigation for wetland impact was unlikely at Bowers Field (ELN), staff began evaluating potential properties for future mitigation sites. Hansen Pit was immediately identified as a high value target, given the multiple wet cells created from past aggregate mining operations. While located in the same geographic watershed, it is sufficiently remote from ELN so as not to cause concerns over bird attraction. As part of our Hansen Pit avulsion study, staff directed a bathymetric survey of existing wet cells associated with the Yakima River. This work is proving highly valuable as we assess the Yakima's likely risk for future avulsion into the pits. Staff anticipates a preliminary report early first quarter of 2021 ahead of FLYING M land closure. It is essential that staff understands any potential additional flood risk to downgradient properties ahead of acquisition. This allows the Flood Control Zone District to mitigate impact tying remediation efforts to the acquisition by providing additional flood risk prevention for the the land seller. PW has spent years planning for key acquisitions along the main stem Yakima River, beginning with the acquisition of agricultural property at Ringer Loop and property downstream of the existing boat ramp. The subsequent acquisition of MFARM and FLYING M create significant environmental mitigation opportunities such as: wetland creation and enhancement, floodplain reactivation and fish enhancement activities. The value of the Advanced Mitigation approach is County ownership. Underscoring confidence in our mitigation efforts by various resource agencies can be attributed to the restrictive covenants associated with our Floodplain by Design acquisitions and our ongoing strong relationship with the Habitat Subcommittee. The Board is well award of staff's efforts preserving the County's sovereignty in land use decision making while maximizing cooperative efforts in this reach of the Yakima River. Our work with the Bureau of Reclamation removing the Schaake Levee, enhancing Spring Creek and moving towards aggressive management of Hansen Pits speaks to our cooperative efforts. Staff is now in the process of scoping next steps in mitigation development. Once we have final avulsion study results, we will reach out to our resource agency partners and attempt to create a consensus -based approach to mitigating Hansen Pits. While the Page 2 of 6 PUBLIC WORKS BOARD OF COUNTY COMMISSIONERS WORK SESSION STAFF REPORT