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The Baldwin Hills reservoir, located 7.5 miles southwest of the Los Angeles City Hall, failed during daylight hours on December 14, 1963. Five lives were lost, scores of homes destroyed, and damages in excess of $15,000,000 incurred.

The reservoir, which was completed in 1951 by the Los Angeles Department of Water and Power, had been hollowed from the head of a ravine on the north slopes of Baldwin Hills. Closure was accomplished by a rolled earth dam approximately 155 feet high across the canyon with five minor embankments placed at low points around the perimeter. The completed structure had a capacity of 897 acre-feet with a water surface area of 19.57 acres.

The foundations of the dams and reservoir consisted of marine sediments of Pliocene and Pleistocene age, comprising largely interbedded sands and silts loosely to moderately consolidated. The site is cut by minor faults associated with the seismically active Newport-Inglewood uplift, source .of the catastrophic Long Beach earthquake of 1933 and the seat of moderate late Pleistocene warping and uplift.

Records of periodic spirit levelings in Baldwin Hills since 1917 have disclosed that the slopes, including the reservoir area, are subsiding, and that a maximum subsidence of about 9 feet had occurred by 1962 at a point about a half mile west of the reservoir. Earth deformation was further manifested by a horizontal shift of nearby triangulation stations and by the development of earthcracks up to 2500 feet in length in the region adjoining the reservoir on the southeast. These deformations were probably influenced both by tectonic activities and production from the Ingle-wood oil field, which flanks the reservoir on the south and west.

The disaster is attributed to the development of an earthcrack similar to those that had earlier appeared southeast of the reservoir. The crack opened along a minor fault mapped by geologists during construction of the project. As a result of this movement, the reservoir floor and the abutment of the main dam were split, creating a narrow passage through erodible sediments in the foundation. Escaping water rapidly enlarged this initial conduit to the point of its collapse. Thus in the final stages of failure Baldwin Hills reservoir emptied through a spectacular breach through the main dam.

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