Supervisors call for San Jacinto River master drainage plan

The County of Riverside’s Flood Control and Water Conservation District will be developing a master drainage plan focusing on the San Jacinto River.

The Riverside County board of supervisors’ members are also the board of the Riverside County Flood Control and Water Conservation District, and April 11, the county supervisors voted 3-0, with Chuck Washington not present and one vacancy, to receive the Stage 3 conceptual planning report for the San Jacinto River and to direct the district to develop a master drainage plan consistent with the conceptual planning report.

In December 2015 the board of supervisors called for the formation of the Lower San Jacinto River Advisory Committee to assist the Riverside County Flood Control and Water Conservation District in establishing a vision to manage the San Jacinto River floodplain between Ramona Expressway and Railroad Canyon. The advisory committee included county Supervisor Marion Ashley, the general manager and chief engineer of the Riverside County Flood Control and Water Conservation District, Perris mayor Daryl Busch and representatives from the Western Riverside County Regional Conservation Authority, the Riverside County Transportation Commission, the Riverside County Transportation Department, the Eastern Municipal Water District, the Endangered Habitats League, the New Perris Specific Plan, the Green Valley Specific Plan and the River Park Mitigation Bank. During five meetings between April 2016 and October 2016, the committee was asked to recommend and rank public health and safety, transportation, environmental and economic goals, to evaluate conceptual management plan alternatives against the ranked goals and to endorse a preferred flood mitigation concept which would serve as the foundation for California Environmental Quality Act analysis and the development of a master drainage plan.

The preferred alternative includes improving Ramona Expressway to ensure that the roadway will not wash out during a 100-year storm event, installing levees along the east side of Interstate 215 at the San Jacinto River to provide 100-year flood protection, constructing wide berms to direct non-storm-related, urban runoff from above Interstate 215 into existing culverts beneath the freeway and into the proposed low-flow channel, a deepened low-flow channel from the Perris Valley Channel to Ethanac Road and an underground storm drain to convey low flows from Ethanac Road to Railroad Canyon. The preferred alternative would support the conservation of more than 4,300 acres of existing floodplain while accommodating incremental development of approximately 2,700 acres.

The next step is for Riverside County Flood Control and Water Conservation District staff or consultants to prepare the environmental documentation necessary to adopt the master drainage plan. The preliminary environmental and engineering analyses will be further developed and refined, which may modify some elements of the project.

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