Coast Boulevard Sea Cave Emergency Stabilization
Project of The Year Finalist / Best Project
Owner: City of San Diego
Lead Design Firm: Dudek
General Contractor: Flatiron West Inc.
Geotechnical Engineer: TerraCosta Consulting Group
Subcontractors: American Marine Corp.; Alvarez and Shaw Inc.; Bob’s Crane Service; ECORP Consulting Inc.; Hayward Baker; Marine Taxonomic Services Ltd.; San Dieguito Engineering Inc.; Zefiro Corp.
This $2.6-million design-build project prevented the collapse of a scenic roadway that serves one of California’s most picturesque beach destinations. Challenges included an underlying dynamic sea cave environment, adjacent protected habitats, limited heavy equipment access and the need to minimize impacts on visitors and local businesses.
The site is located 500 ft from La Jolla Cove, surrounded by cliffs and adjacent to other environmentally sensitive areas. The underwater environment is rich in marine life, while the location is popular with kayakers, snorkelers, swimmers and scuba divers.
Divers removed sand and debris from the cave and filled its floor and crevices with a specially formulated erodible concrete mix that stabilizes the roadway and surrounding areas and provides long-term protection of the critical infrastructure above. Designed to erode at the same rate as the adjacent rock, the concrete ensures that repairs will not intrude on the area’s natural aesthetics.
Crews on the bluff drilled cased borings in the roadway and pressure grouted the cave from above to further ensure the stability of the fill. The successful application of the new concrete mix product offers a viable repair option elsewhere in California and other states where coastal erosion is a significant issue.
A prefabricated biofiltration unit proved instrumental in installing a new storm drain system located at the cave entrance, providing a direct discharge to the ocean. Although biofiltration units are typically project specific, use of the previously fabricated system cut manufacturing and delivery time by more than six weeks, helping to limit the entire construction process to just three months.
To reconstruct damaged concrete roadway and sidewalks, a decorative, stamped concrete pavement maintains historic surface patterns. Pavement elements accommodate both vertical and horizontal curves as well as anticipated tie-ins at each end for integration in future roadway projects. Carefully sequenced concrete pours created the intended patterns without delaying project completion.