Coast Boulevard Sea Cave Emergency Stabilization | Submitted by Flatiron West Inc.
Region: ENR California
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.
A failing sea cave leading to extensive cracking in the roadway at a popular tourist destination had the makings of a disaster. The solution was a $2.6-million design-build project, but with work in a sea cave surrounded by sea lions and seals and in a culturally sensitive area, it was also fraught with potential pitfalls. Three months after starting, however, the team of contractors and divers had stabilized the cave, repaved the roadway above and relocated a storm drain and outfall—all without a single safety incident.
“It’s quite the little project that could,” says Russ Bergholz, an engineer at Dudek, which worked with Flatiron West and TerraCosta Engineering Group on the project. TerraCosta had been monitoring the cave for more than a decade and alerted San Diego when the curve in LaJolla appeared to be at imminent risk of failure. The city closed Coast Blvd. immediately.
To stabilize the cave, divers entered it and filled the cave floor and crevices with concrete that will erode at the same rate as the surrounding cave. Workers above drilled into the cave and filled it with grout. “We chased the work around the clock,” says Michael Rissi, Flatiron project manager.
To reduce wave action into the cave and allow the concrete to set, massive barriers and sandbags were placed at the entrance. Divers worked to place the concrete, while other divers were at a constant vigil to keep wildlife away.
Filling up the cave also filled a stormwater outlet, which had to be replaced. “We were designing on the fly,” Bergholz says.
Both Bergholz and Rissi attribute the project’s success to relationships the team had previously developed, as well as to new ones TerraCosta had with the U.S. Army Corps of Engineers that helped expedite needed permits.