An article by the NZ Herald reports that recommendations for slope monitoring and early warning made by a geotechnical consulting firm in a report 2 years before the initial failure were not adopted by Auckland Transport. The Birkenhead landslide initially took out 25 parking spaces in a retail area in October of 2017, and a larger landslide in November of the same year took out a micropile or other drill rig working to stabilize the site. Local officials defended the decision, indicating that they instead opted for regular site visits and visual observation of cracks noted in the report. The initial recommendations by GHD Engineers included the monitoring as a minimum, and also recommended several stabilization options in the range of $500k. The current estimates to repair the landslide are $14M to $24M.
On September 17, CALTRANS and Kiewit Pacific held a "tunnel excavation celebration" to kick off the start of tunnel construction on The Devil’s Slide Tunnels project on California State Route 1 (the Pacific Coast Highway) in San Mateo County between the town of Montara to the south and the city of Pacifica to the north. The project involves the creation of a separated two-lane road, one lane in each direction. This road will pass through twin tunnels, over twin bridges and connect with an existing non-separated two-lane road at each end. The new road will be approximately 6,500 feet long, made up of the roughly 4,000-foot twin tunnels, the 1,500-foot north approach road (which includes the 1000-foot parallel bridges), and the 1,000-foot south approach road. Upon completion, the new road will bypass geologically unstable portions of existing Route 1, sections of roadway subject to lengthy closures, high maintenance costs over the years, and risk of permanent failure. Thanks Geology.com for the heads up. [Read on for more background, photos, maps, and movies!] (Images by CALTRANS)