Crews began placing two-to-six-ton boulders along south Carlsbad Boulevard during the week of Oct. 5 to stabilize an eroding coastal bluff that threatens the highway.

A large crane arrived Tuesday, Oct. 6, to lift rock from the roadside down to the beach near Las Encinas Creek, according to a city newsroom post published Friday, Oct. 9. Boulder deliveries began during the week of Sept. 29.

The southbound bike lane on Carlsbad Boulevard between Solamar Drive and Island Way is closed for the duration of construction. The city is asking drivers in that stretch to plan for extra travel time.

The bluff is eroding.

The project extends the existing rock revetment approximately 192 feet to the north. That revetment already runs 1,270 feet along the base of the bluff, with 750 feet installed in 2009 and 520 feet added in 2015 and 2016, the San Diego Union-Tribune reported in September.

City staff first observed bluff erosion along south Carlsbad Boulevard during a routine inspection in June. An independent geotechnical firm hired in mid-July concluded the bluff needed emergency stabilization. The city received that report Sept. 8 and declared a local emergency the next day, Sept. 9, to fast-track contracting and permitting.

A Union-Tribune reporter who visited the site Sept. 10 described waves eating away the base of the bluff north of the existing revetment. The erosion had left a steep cliff of soft earth 20 to 30 feet high on the seaward edge of the highway.

City Manager Geoff Patnoe said in the city's Sept. 9 emergency declaration that the work is part of a broader effort to protect infrastructure ahead of a potentially strong El Niño season. "We understand this is a heavily traveled roadway, and maintaining its integrity is essential to protecting public safety," Patnoe said at the time.

The city is working with the California Coastal Commission on the emergency permit needed for the project. Construction is expected to continue through late 2026.