Construction crews will descend this fall on Del Mar’s southern bluffs for three to four months of urgent repairs beneath and around a 1.5-mile stretch of railroad, focusing mostly on drainage infrastructure and related fixtures that have rusted through, eroded and in some spots collapsed altogether.
The $3 million project, led by the San Diego Association of Governments (SANDAG), marks the fourth round of bluff repairs over the past 20 years.
A team of SANDAG engineers and geologists described the project, known as “Del Mar Bluffs Stabilization 4,” to the Del Mar City Council on March 5. Pending approval from the California Coastal Commission, SANDAG is “trying for September, October, November” to carry out the repairs, said Bruce Smith, a SANDAG senior engineer.
Work crews will access the beach at two points: the 17th Street Lifeguard station and Torrey Pines State Park. Access to the bluffs will come via Coast Boulevard for work on six spots between 7th and 12th streets.
Tricia McColl, the project’s chief design engineer, laid out the various repairs:
1. At 11th Street, SANDAG will rebuild the headwall and drainage pipe that have collapsed into a pile of rubble on the beach.
2. Three sections of timber retaining wall have degraded far faster than expected, bringing them “very close to the end of their useful service life.” SANDAG will install new pile supports and reinforce the walls in a way that retains the wood lagging.
3. The stormwater chute at 12th Street has become increasingly unstable, McColl said, especially after heavy rains. Crews will pour concrete to strengthen its precarious foundation. Ultimately, SANDAG wants to replace the chute with an underground storm drain, McColl said, but that funding has yet to materialize.
4. A section of the bluff between 6th and 8th streets has been particularly damaged by runoff from the homes above. The bluff above the rail collapsed at 7th Street, and the drainage channel running atop the bluff has fallen into disrepair. The bluff face will be restored and the channel replaced, as well as its adjacent walking path.
5. Just north of 10th Street, a storm drain has seen accelerating decay and its adjoining wall “has completely failed,” McColl said. SANDAG plans to drill a new soldier pile there with a lagging wall as support.
Even after the upcoming round of work, the bluff will be far from stabilized. Repairs to another 800 feet along the rail—five separate sections ranging from 90 feet long to 200 feet long—are “slated for some time in the future,” McColl said, but funding has not yet been allocated.
SANDAG’s two-decade strategy of patchwork repairs on Del Mar’s bluff was intended as a stopgap until the railroad could be moved into a long-discussed tunnel, presumably along or under Interstate 5. With the tunnel nowhere in sight, SANDAG is working on a plan to stabilize the bluff enough between 2020 and 2030 that the railroad can stay where it is for another half-century.
“Depending on how episodic the failures are and how fast the bluff retreats, that could cost anywhere from $40 to $80 million,” Smith said.