Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole.
Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter.
Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.
Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.
OCR for page 197
Appendix F
The Failure of the Baldwin Hills Reservoir Dam
On December 14, 1963, the dam built to contain the Baldwin Hill Reservoir located in
southwest Los Angeles failed, releasing 250 million gallons of water into the housing
subdivisions below the dam. Approximately 277 homes were damaged or destroyed and five
people were killed by the disaster (Hamilton and Meehan, 1971). Although there is speculation
that waterflooding operations in the Inglewood Oil Field (located to the west and south of the
reservoir) were partially to blame for the failure of the reservoir dam, the dam itself did not fail
due to an induced earthquake. Records from the Seismographic Laboratory of the California
Institute of Technology located 15 miles northeast of the reservoir showed no earthquakes large
enough to cause internal damage to the reservoir during the period 1950-1963 (Jansen, 1988).
Instead, the sealing layers in the floor of the reservoir failed due to the “creep” of several
geologic fractures below the reservoir, which caused the release of water through the floor of the
reservoir that resulted in the structural failure of the dam itself.
The Baldwin Hills Reservoir was constructed between 1947 and 1951 by the Los Angeles
Department of Water and Power. The reservoir was constructed on a hilltop and was formed by a
dam on the north side and earthen dikes on the other three sides, which were constructed of
materials excavated from the reservoir bowl. The soil under the reservoir was composed of
porous material and was bisected by three known geologic faults (Jansen, 1988). The floor of the
reservoir was made watertight by the use of two layers of asphalt with compacted earth between
them. Below the upper layer of asphalt and earth, a level of pea gravel with tile drains was
installed to allow the monitoring of leakage from the bottom of the reservoir. Extensive
discharge from the drainage system was recorded during the initial filling of the reservoir, and
filling was discontinued until repairs to the reservoir could be made (Jansen, 1988). Cracking in
concrete portions of the reservoir was noted as early as 1951.
The Inglewood Oil Field was discovered in 1924 and covered approximately 1,200 acres
when fully developed. At the time of the failure of Baldwin Hills Dam in 1963, the field had
more than 600 producing wells, and the closest wells were located within 700 feet of the
reservoir structure. The oil reservoir is divided into multiple compartments due to a series of
geologic faults. Several of these faults not only divide the Inglewood Oil Field but also continue
to the surface and are present on the site of the Baldwin Hills Reservoir. The depth of the wells
in the Inglewood Field is between 2,000 feet and 4,000 feet. Due to subsurface fluid withdrawal,
the ground level above the field exhibited a surface subsidence of approximately 10 feet by 1964.
In order to increase production, waterflooding operations were commenced in 1954 and
expanded in 1955 and 1961. These injection operations increased pore pressure in portions of the
197
Prepublication version – Subject to revision
OCR for page 198
198 APPENDIX F
oil field from 50 psi to over 850 psi by 1963 (Hamilton and Meehan, 1971). Injections depths
were as shallow as 1,200 feet.
The dam structure failed due to subsurface leakage of reservoir water beneath the floor of
the impoundment and under the foundation of the dam itself. The subsurface leakage was caused
by a crack seal extending across the floor of the reservoir in line with the breach in the dam
(Jansen, 1988). Movement of the geologic faults crossing the floor of the reservoir with
downward displacement of 2 to 7 inches on the western side of several faults caused cracking in
the asphalt membrane seal and allowed water to enter the porous soil beneath the dam. Later
excavations of the bottom of the reservoir indicated that leakage had occurred for an appreciable
amount of time before the dam failure. The slow movement of the faults beneath the reservoir
has been attributed to either 1) natural causes inherent in the geologic setting; 2) subsidence of
the ground surface caused by oil and gas operations or by the filling of the reservoir with water;
or 3) pressure injection of water in the Inglewood Field at shallow depths for oil and gas
operations and in the presence of a fault system.
REFERENCES
Hamilton, D.H., and R.L. Meehan. 1971. Ground Rupture in the Baldwin Hills. Science
172(3981): 326-406.
Jansen, R.B. 1988. Advanced Dam Engineering for Design, Construction, and Rehabilitation.
New York: Springer.
Prepublication version – Subject to revision
