This section is a brief review of problems arising from unusual conditions and operations in the Baldwin Hills area of Los Angeles.

First, note the setting: an anticlinal dome in the middle of the (otherwise subsiding) Los Angeles basin, with active periodic tectonic movement.

In December of 1963 the newly constructed baldwin Hills Reservoir failed with five deaths and a great deal of property damage. The event was captured on TV. (See recent "Wrath of God" episode on the Discovery channel for live coverage of the failure.)

Here is a view of the cracked dam after the failure, looking south.

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Also a view of the reservoir floor, showing the crack in the lining. The ground is offset down to the left.

The role of central graben subsidence, accelerated by oil extraction, supplemented by reinjection of waste brine into the ground, on fault movement beneath the reservoir is indicated in the animated graphic following. Injection pressures exceeded hydrofracture pressures and the recorded timing of the fault offset (which was dutifully recorded by the reservoir owner) indicate the injection as being the decisive factor. (See references)
 

A comparable condition developed in the nearby Salt Lake oil field in 1985. Here, the waste brine migrated along a fault toward the surface, releasing methane an causing the explosion of a Ross Dress store.

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Note the injection and extraction depths and general dimensions and geology are comparable to Baldwin Hills. Also, below, the apparent reduction in waste brine production that preceded the Fairfax accident. See references below where the likelihood of unrecorded waste disposal leading to fluid migration is discussed.
 

Most recently the Baldwin Hills are proposed as a site for new housing to be built on fill on top of the northwest part of the oilfield. The potential for gas migration clearly exists and should be evaluated in the EIR for such a project so that appropriate mitigation measures (well surveys, gas testing and monitoring, injection history and pressure analysis, design of protective venting, etc) can be employed.
 
 

Fault or ground cracking reactivation is also a hazard as in the case of the reservoir. In late 1999 indications of fresh ground cracking

was noted in the northwest quadrant of the Baldwin Hills, a likely response to injection operations nearby. Notice the active ground cracking photographed just to the north of the project.

Attempts to maximize proposed lot area on top of the hill results in this case in excessively steep fill slopes (2:1 in sand) steepened further by use of reinforced earth walls ("Loffel walls").  The reported maximum ground acceleration for future earthquakes is 0.53 though this does not take into consideration topographic amplification which could make ground motion even stronger in the upper slope. In any event standard "pseudostatic" stability analyses with "standard" ground accelerations of 0.15g, yielding low factors of safety, do not provide adequate information for evaluating the magnitude of displacement during earthquakes. A more realistic analysis would suggest a strong probablility of slope movements of at least several inches.
 
 
 
 
 

ANNOTATED REFERENCES:

Meehan, RL (1984):" The Atom and the Fault: Earthquakes, Experts, and Nuclear Power", The MIT Press, Boston. This book discusses the evaluation of geologic fault hazards v. high hazard facilities in California.

Meehan, RL; Hamilton, DH (April 23, 1971): "Ground Rupture in the Baldwin Hills," Science. 172, no. 3981, 333-344.  This report describes the role of oil drilling and water re-injection in causing the Baldwin Hills Dam collapse.

Meehan, RL; Hamilton, DA (Spring 1992): "Cause of the 1985 Ross Store Explosion and Other Gas Ventings, Fairfax District, Los Angeles," Engineering Geology Practice in Southern California. 20. This report describes how water-flooding operations can lead to methane hazards  in and around oil fields.