A Storm Drain Success Story: Two Tunnels and a Landslide

Discover the challenges and the innovations associated with a storm drain project sporting a construction cost of $15.1 million along San Ramon Canyon in the affluent coastal city of Rancho Palos Verdes in Los Angeles County.The east side of the canyon was suffering from cyclical deposition of soil from the active Tarapaca Landslide, which resulted in 30-foot vertical slopes that filled the canyon and allowed large rain events to deliver sediment and floodwater to 25th Street below. More than 250 homes were in harm’s way and access was threatened to both 25th Street and Palos Verdes Drive East (PVDE) switchbacks. The Harris Team developed an elegant solution using trenchless technology, which required two tunnel s and a gravity buttress fill design to divert the collected stormwater to the ocean at the bottom of the coastal bluffs, shore up a deficient drainage system downstream and mitigate the runoff inspired transport of debris from an active landslide.