Lake Forest Woods Sewer and Manhole 36 – Emergency Erosion Protection

Owner: Irvine Ranch Water District

Project Location: Lake Forest, California

January 2023 storms eroded the banks of San Diego Creek in Lake Forest, exposing a 10-inch sewer pipeline and manhole shaft that ran alongside the creek. With more storms likely, the line was at risk of failure. Irvine Ranch Water District awarded Larison the emergency repair on February 1, 2023, and Larison completed the work in a single day on February 11, well ahead of the 30-day deadline.

Crews placed Type III non-woven filter fabric, a layer of Class II (60 lb) rip rap, and an armor layer of Class VII (½-ton) rip rap on a 1.5:1 slope, extending several feet into the creek invert to protect the pipeline and manhole from future storm flows.

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This repair was accomplished using Class VII (1/2-ton) ungrouted rip rap over Class II (60 lb) ungrouted rip rap over Type III non-woven fabric. The rip rap was keyed into the creek invert several feet and was placed on a 1.5:1 slope from below the creek bed to the crest elevation.