Earthquake Damage and Repairs at Austrian Dam

Austrian Dam, a 185-foot-high earthfill embankment owned by the San Jose Water Company, was the closest major dam to the epicenter of the Magnitude 7.1, October 17, 1989 Loma Prieta Earthquake (about 8 miles), and was the Most severely damaged. The crest of the dam settled over 2-1/2 feet over much of its length, and moved over l-foot downstream at its right end and l/2-foot upstream at its left end. The reservoir (Lake Elsman) was at an unusually (and fortunately) low level at the time of the earthquake. However, the late season dictated immediate action to repair the dam and spillway prior to the onset of winter and filling of the reservoir. Exploration was performed concurrently with the repair work, and construction details were designed and modified as the extent and nature of damage was defined. The principal spillway and earthwork repairs were essentially completed in about an 8 week period immediately following the earthquake. At the peak of the remedial construction, about 3 weeks following the earthquake, work was proceeding simultaneously on the upstream slope, both ends of the dam, and the spillway, working 7 days a week. Major site difficulties included the very congested work areas, the near-absence of material storage and processing areas, and the ruggedness of the particularly as it affected landslide remediation primary sources of earth borrow.