The City of Santa Cruz has been battling the forces of the ocean on West Cliff Drive for decades as bluff retreat slowly impinges on the pedestrian walkway and the street itself. Pacific Crest Engineering, as a member of a design team, aided the City in considering their options for decreasing bluff retreat rates at two sites on this scenic road. Our soil borings in conjunction with the geologists’ assessment concluded that the road in one of these locations is underlain by an ancient sea cave that was filled in and paved over in the early 1960’s. Our design team presented the City with several optional approaches for repair including soldier pile walls, sea walls and revetment/rip rap maintenance. Along with the repair alternatives, relative costs and lifetime expectancy were also provided so that the City could complete their cost-benefit analysis for both short and long term solutions.
Heavy rains in 2016-2017 caused failure of retaining walls that separate a residence from a 115-foot high bluff above the beach in Aptos, California. Access of equipment to the top of the slope was not possible due to the tight configuration of existing structures. Soil borings were advanced at the top of the bluff using portable drilling equipment to obtain soil samples for testing. Based on our subsurface investigation and slope stability analyses, a soldier pile wall was designed to retain the materials at the top of the slope and protect the residence from on-going slope movement. Two-foot by three-foot rectangular soldier piles approximately 30 feet deep were hand dug at the top of the slope by a specialty contractor. Our field inspectors entered the properly shored hand dug holes to observe the subsurface conditions and confirm that adequate soil bearing conditions were present. Surficial soils were then stabilized by installation of a coconut fiber turf reinforcement and plantings of native grasses and shrubs.
A new two-story residence will replace an existing residence on the south side of Las Olas Drive. The property fronts a sand beach and the Monterey Bay, and is mapped as being susceptible to coastal erosion and flooding. The new residence will be supported by a wharf‑type foundation system designed to elevate the residence above the projected coastal flooding elevation to protect it from coastal flooding and erosion hazards. The structure foundation has been designed to resist the lateral forces imposed on the structure due to wave, debris, and hydrodynamic forces. The number of vertical piers and the extent of horizontal bracing have been minimized to avoid obstructing water and debris movement and the projected extent of flooding below the residence.
444 Airport Blvd, Suite 106, Watsonville, CA 95076 · 831-722-9446
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