The Tramonto Slide State Route 1 at Porto Marina Way
Location
Northbound State Route 1 (Pacific Coast Highway/PCH) at Porto Marina Way, ¾ miles north of Sunset Boulevard, in Pacific Palisades (the city of Los Angeles).
The Slide
The Tramonto Slide is approximately 3 acres in size on the north side of PCH.
Background
The slide area referred to as the "Tramonto Slide" is much larger than the portion visible on the highway. It is approximately three acres in size and has been moving intermittently since 1939. In the past Caltrans Maintenance crews have been able to clear slide debris on the highway to the northbound shoulder of PCH to reopen lanes.
The most recent slide activity originated outside of state/Caltrans right of way, caused by a storm in early February 2024, and further saturated by a second storm in February and two more storms in March 2024. The slide encroached onto Caltrans right of way, blocking the northbound right lane of two.
A joint study was done in 2010 by Caltrans and the City of Los Angeles, one of the property owners. The study documented the history of the slide and recommended that long-term repairs start from the top of the slide.
After waiting for weeks for the most recent slide incident to dry out, the Caltrans Geotechnical Division determined the unstable nature of the slide prevents Caltrans from removing the debris from the northbound right lane of the highway near the toe of the slide and that repairs still need to start from the top of the slide, which is outside of Caltrans' jurisdiction and right of way. Once reopening the right lane was ruled out, Caltrans moved forward with a plan to create an additional northbound lane by reconfiguring the remaining lanes.
Research by the Caltrans Right of Way Division has determined that most of the property near the top of the slide is privately owned and some of it is owned by the city of Los Angeles. Once the slope has been stabilized from the top, Caltrans can continue with repairs at the bottom of the slide.
A permanent resolution to the Tramonto Slide area must be determined through communication with the owners of the property outside of Caltrans' right of way. Long-term mitigation may require construction of infrastucture on private property, including multiple retaining walls. There is no estimate of when a mitigation plan will be established, but Caltrans is communicating with the city of Los Angeles on the issue.
The Lane Closure
Since the slide is too unstable to clear the dirt from the northbound right lane, Caltrans realigned lanes on the Pacific Coast Highway to create a second northbound lane. There was no additional space in the median to create another lane. All northbound and southbound lanes were shifted towards the shoreline to create space for a second northbound travel lane that allowed the safe and smooth flow of traffic.
Construction included removing the existing curb along the southbound shoulder; removing existing pavement delineation, markers, and markings; realigning lanes around the slide area; grinding; repaving; restriping; installing signs; and placing k-rail at the toe of the slide.
The additional northbound lane was opened to traffic the morning of Thursday, May 30, 2024.
Contact Information
Marc Bischoff Public Information Officer Caltrans - District 7 Marc.Bischoff@dot.ca.gov