33 Bay Drive Landslide

Ninyo & Moore provided geotechnical consulting services during the evaluation and repair of active landsliding and damaged foundations for a bluff top home. The four-story home cantilevers outward over a coastal bluff, which includes an active landslide area. Several homes were destroyed during the past 40 years due to landslide movement. Landsliding resulted from adverse bedding within fine grain siltstone facies of the San Onofre Breccia coupled with numerous fault planes. Our geologic evaluation was conducted concurrent with investigation and repair activities on adjacent properties, and included geologic mapping of the bluff and landslide deposits, downhole logging and sampling of two large diameter borings, hollow-stem auger drilling and continuous coring of one boring, slope stability analysis, and preparation of repair recommendations. Recommendations for repair included CIDH shoring piles, tie-back anchors to stabilize existing pier foundations, shear key buttress design, toe erosion protection wall, subsurface drainage system, and a soil nail wall for upper bluff stabilization. Construction services included geotechnical and materials testing during installation of CIDH piles, tie-back anchors and soil nails, geologic evaluation and as-graded mapping during excavation of landslide deposits and construction of the shear key, evaluation of subsurface drainage system installation, and compaction testing during buttress construction.