Ocean Trails Golf Course
(Trump National Golf Club)

Ninyo & Moore performed a forensic evaluation of landsliding at the Ocean Trails Golf Course. On June 2, 1999, an approximately 16-acre ancient landslide on the coastal bluff was reactivated, sliding approximately 50 feet toward the ocean. The ancient landslide destroyed much of the 18th fairway and green along with adjacent improvements, including an active County sewer line. The geologic setting included gently to moderately tilted beds of the Monterey Formation. The Monterey Formation at this locality included interbedded sequences of fine silty sandstone, siltstones, shales, dolomitic shales, siliceous zones, and bentonitic ash beds. The basal rupture surface was formed along a relatively continuous bentonite layer at a depth of approximately 90 feet. The geologic evaluation included detailed geologic mapping, 26 large-diameter borings, two rotary wash continuous core borings, 12 inclinometers, and the excavation and evaluation of buried sewer lines and artificial lakes. The analysis included preparation of multiple geologic cross sections, slope stability analysis, and evaluation of potential reactivation causes including seismic activity, precipitation, wave erosion, irrigation, construction activities, lake leakage, and sewer line leakage.