Addendum No. 1 to the Syphon Reservoir Improvement Project Final Environmental Impact Report

Addendum No. 1 to the Syphon Reservoir Improvement Project Final Environmental Impact Report

IRWD prepared a Final Environmental Impact Report (FEIR) for the Syphon Reservoir Improvement Project (SRIP) (State Clearinghouse No. 2019080009), and a Notice of Determination (NOD) approving the project was filed in compliance with Section 21108 and 21152 of the Public Resources Code on July 26, 2021. The SRIP would increase the storage capacity of the Syphon Reservoir from 500 acre-feet to approximately 5,000 acre-feet to serve the community’s seasonal and future recycled water needs. Increased use of recycled water will make more drinking water available and help withstand future water shortages. The SRIP FEIR determined that construction of the expanded reservoir would result in impacts to woody riparian and freshwater marsh habitats and stipulated that both on-site riparian/wetland habitat creation and off-site habitat mitigation would be provided to assure that no net loss of such habitats would occur and also to provide appropriate compensation for temporary loss of habitat value (i.e., temporal loss). SRIP FEIR Mitigation Measure BIO-4 noted that IRWD was working with the wildlife agencies to develop a mitigation program and stipulated that off-site land would be set aside for creation or restoration of habitat. At the time the SRIP FEIR was certified, a site had not yet been selected for the off-site riparian and wetland habitat mitigation component. In 2023, after extensive consultation with United States Fish and Wildlife Service (USFWS) and the California Department of Fish and Wildlife (CDFW), the off-site mitigation area was selected at a 33.4-acre IRWD property in the San Joaquin Marsh south of Campus Drive in Irvine, California. USFWS and CDFW have accepted the overall mitigation package in concept and agreed that the implementation of proposed riparian/wetland mitigation, both on-site as part of the SRIP and off-site at the San Joaquin Marsh site, would adequately compensate for all impacts to riparian and wetland habitat and associated wildlife identified in the SRIP FEIR. The off-site riparian and wetland mitigation component at the San Joaquin Marsh is herein referred to as the Proposed SRIP Off-Site Mitigation. The purpose of this Addendum No. 1 is to describe and evaluate the potential environmental effects associated with the proposed SRIP Off- Site Mitigation (Public Resources Code §21166; California Environmental Quality Act [CEQA] Guidelines §15162; CEQA Guidelines §15168(c)(2)).

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