Timeline of the destruction which has already occurred on Edgehill Mountain
Jan. 17, 1952: A significant landslide near the top of Edgehill Mountain undermined the foundation of a home (which began to slip down the hill), threatening the privately-maintained Edgehill Way. The Cahill family house at 275 Edgehill Way was evacuated.
Jan. 24, 1967: Several tons of rock and mud cascaded onto Nazarene Church property – a warning of progressively more serious landslides to come.
1978: The ongoing threat posed by continuing landslides forced the Nazarene Church to evacuate their facilities; the congregation was not able to return to the site until 1987. In order to pay for clean-up, engineering, retaining walls and other remediation measures, the church had to sell most of their property situated south of the church. After the Greater West Portal Neighborhood Association helped defeat a controversial 150-unit housing plan, the developer secured neighborhood approval to build 13 homes at what is now Knockash Hill Court.
February 1982: Tumbling rocks – up to three feet in diameter – crashed into the Happy Times Nursery School building and schoolyard west of the Nazarene Church. Following one rockslide, which during "naptime," the nursery school vacated the site permanently. By the end of the decade, the large field at the base of the slope was almost completely buried by accumulated slide debris.
Feb. 17, 1995: A large rockslide crossed the road at the base of the slope, impacting new homes at the west end of the partially completed development. The slope failure originated in the vicinity of previous rockslides that took place during the winters of 1993 and 1994, in the early phases of the residential development at Knockash Hill. Following an inspection, the engineering firm of Dames & Moore declared the area safe and construction was allowed to continue.
Jan. 5-18, 1997: Following two rockslides in December 1996, massive landslides undermined Edgehill Way (overlooking Ulloa Street) to the point of total collapse as more than 100 tons of boulders, mud and debris overwhelmed a 10-foot tall retaining wall, crossed a street and slammed into four new buildings on Knockash Hill, reaching the second floor balconies. Residents of the 13 homes, including former SF Police Chief Fred Lau, were evacuated for an extended period of time as an extensive clean-up, risky remediation effort and dangerous demolition of a clifftop house above Knockash Hill were completed. A boulder the size of a washing machine sat for months at the entrance to the church – a silent reminder not to underestimate the forces of nature.
1998: After excavation exposed saturated soil in a steep, destabilized portion of Edgehill Mountain, a rockfall originating in the adjacent Open Space overwhelmed a 60-foot-tall retaining wall, dumping rocks, clumps of clay and debris onto the construction site of three houses on Kensington Way near Ulloa Street. The slide necessitated the emergency construction of a third, previously unplanned, retaining wall. Cracks in the foundation, several vigorously spurting leaks and water seeping through the concrete were apparent almost immediately. Twenty years later, drainage problems continue as groundwater continues to pour out of the base of a telephone pole at the corner of Kensington Way and Ulloa Street. As a result of neighborhood opposition, unexpected problems, work stoppages and cost overruns, the developer lost money on the three-home project, which took five years to complete.