4.2.2 Baldwin Hills Dam

On December 14, 1963, an unpredicted flow of water occurred at Baldwin Hills Dam in LA, California. The water came from drains under the reservoir lining. Muddy leakage was discovered downstream from jthe north side of the reservoir. At 2:20 pm, lowering of the reservoir water level revealed a 3-ft-wide break in the reservoir’s inner lining. Water broke violently through the downstream face of the dam. By 5:00 pm, the reservoir had emptied, revealing a crack in the lining extending across the reservoir bottom in line with the breach in the dam.

Failure progress
• At 11:15 am, caretaker observed excessive flow in the drainage inspection chamber beneath the reservoir.
• At 1:30 pm, the LAPD was requested to start evacuation.
• At 2:20 pm, sigalert broadcast on radio and television.
• At 3:38 pm, the dam was breached.

This dam was constructed on April 18, 1951. Located at the head of a northward-draining ravine, the reservoir was formed by the dam on the north side and compacted earth dikes on the other sides. Designed as a homogeneous earthfill, the dam was 232ft (71m) high and 650ft (198m) long.

The embankments were constructed of materials excavated from the reservoir bowl. Two separate underdrain systems were provided, one to drain the foundation under the earth embankments and the other to collect seepage passing through the earth lining and convey it through a central observation and measurement chamber to an outfall pipe.

As a result, five people died & scores of homes destroyed. Total damage estimated at $15,000,000. Early warning and prompt action had averted a much greater tragedy.

2:20 pm 3:25pm
3:30 pm 3:38 pm

3:40 pm

Photo: Baldwin Hills Dam, progress of failure per time, Courtesy: Los Angeles Times

Lessons Learned (Leps and Jansen)

- Foundations in erodible rocks must be thoroughly explored to disclose any preexisting cavities or other defects.
- The total prevention of leakage into a reservoir foundation over the lifetime of the facility may be unattainable under usual circumstances.
- The possibility of differential fault movement unrelated to tectonic activity must be considered.
- Drains should be amply sized and provided with access, where possible, to facilitate maintenance.
- Surveillance of a reservoir must be extended to its environs and to the consequences of adjacent developments and physical changes.

Resource:
- Investigation of Failure – Baldwin Hills Reservoir, California Department of Water Resources, 1964
- Ross Boulanger, Baldwin Hills Reservoir Failure 1963, In-class handout, 2008
- Thomas Leps and Robert Jansen, The Baldwin Hills Reservoir Failure, Advanced Dam Engineering for Desing, Construction, and Rehabilitation, edited by Robert Jansen, 1988, Van Nostrand Reinhold, NY.