Landslide

January 25, 1998 February 3, 1998

February 9, 1998

Following a period of heavy rains, a horizontal crack appeared about midway up the face of the 175 ft. hill where twelve proposed housing units are planned for the flat area at the top (Bench A). By January 25, 1998, a small section of the hill had broken away and fallen onto the driving range (upper left; partly covered by the blue tarp). By February 3, the hillside gave way as shown in the photo at upper right. By February 9, the landslide had widened up to approximately 300 ft.

This proposed housing site lies between two branches of the active Hayward Fault . "The Hayward Fault is currently considered by geologists to be the most dangerous in the Bay Area", (Lowney Associates, Geotechnical Investigation; Boulders Residential Development; 1997, page 18). The main branch of the Hayward fault passes horizontally along the near side of the driving range. A secondary branch of the fault crosses the far side of the hill where a "buttress" is proposed to help stabilize slopes that are even steeper than the ones in this picture. This site can expect surface rupture and severe ground shaking in the event of a large magnitude earthquake along the Hayward Fault. This site has landslides now. Imagine what will happen when a large magnitude earthquake strikes.

A local newspaper did a story about this proposed housng project.in which the City of San Leandro Planning Manager was quoted as saying, "They're basically [to be} built on rock, and that's the best soil you can get." (The Daily Review; Hayward, California, November 18, 1997.) We don't agree. If you think this is a bad location to put a housing project, please send a message to San Leandro City Officials and let them know.

In this most recent photograph, the landslide has continued to widen to approximately 300 ft. with signs of surface erosion to the left of the main slide area.

Lake Chabot Road is the only emergency access and evacuation route for the proposed housing project. Lake Chabot Road was closed on February 3, 1998 due to fallen trees and landslides, including one small landslide at Bench C. This lifeline will also be closed when the Hayward Fault produces surface rupture or seismically induced landslides. According to the EIR, "Fault rupture at the project site would isolate some residence (sic) from the main access road into the subdivision.", (Boulders Residential Development Environmental Impact Report, page 3.4-16).