Orange County Transportation Authority MP 206.8 Track Stabilization


Orange County Transportation Authority


San Clemente, California

Project Overview

The railroad was constructed along the base of the coastal bluff in the early 1900s and a residential development was constructed at the top of the bluff in the late 1960s. Both the railroad and the residential development were built on top of an ancient landslide. The landslide was remobilised in 2021, damaging several homes and moving the railroad tracks more than 2 feet laterally. Temporary stabilization of the railroad was installed immediately by placing 11,500 tons of riprap at the toe of the slope, and the tracks were realigned; however, the landslide started moving again in the fall of 2022 and passenger rail service was halted to allow for a more permanent repair.

Engeo's Role

ENGEO and Condon Johnson were engaged to design and construct a system to stop the landslide from additional lateral movement, to protect the railroad tracks, and to get the commuter train back up and running as quickly as possible. ENGEO provided a full geotechnical and civil design and prepared the civil construction drawings for a tied-back grade beam stabilization system.

Challenges & Solutions


  • The project had to be designed as a long-term solution but executed quickly as an emergency response with limited subsurface characterization. So, timelines were tight and selection of appropriate engineering model parameters was challenging.
  • Also, the landslide affected the housing development above the railroad right-of-way, but OCTA did not own that property and therefore did not have complete access to all the impacted properties.
  • Maintaining adequate temporary stability while limiting movement during construction.


Grade beam and tie-back retaining solution and temporary construction shoring design. The construction of our design allowed passenger rail service to reopen on February 4, 2023.


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