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NPS Form 10-900 OMB No. 1024-0018
(Rev. 8-86)
United States Department of the Interior
National Park Service

National Register of Historic Places
Continuation Sheet

Section number 8 Page 11

St. Francis Dam (Site of), Los Angeles County, California — Narrative Statement of Significance
[continued]
Rejecting the sabotage theories, the Governor’s Commission concluded that the dam’s failure began on the western abutment, where
it crossed the San Franciquito fault, pointing to the possible hydraulic piping Mulholland and Van Norman were asked by damkeeper
Tony Harnischfeger to examine the day before the failure, as well as their interpretation of the downstream distribution of the dam’s
concrete blocks. The landslide on the eastern abutment, they concluded, was caused by it being undermined by eddying flows pouring
through the failed western side of the dam. [Figure 18]

As later, more thorough, investigators into the St. Francis Dam failure were to point out, the Governor’s Commission committed
numerous analytical errors born of the political necessity of drawing rapid conclusions from the tragedy and ending the rumors of
sabotage. As the first report issued on the collapse, however, the Governor’s Commission report would overshadow the engineering
and geology literature for decades thereafter.

In the final accounting, William Mulholland accepted complete responsibility for the failure of the St. Francis Dam, and was widely
praised for his humility in the face of the tragedy. Taking immediate action where he was still able, he ordered the water level in the
similarly-designed Mulholland Dam above Hollywood to be lowered. During the 1930s, this dam would be substantially retrofitted.

Although Mulholland acknowledged that his office must have overlooked some important consideration in the design of the St.
Francis Dam, he expressed dissatisfaction with the official verdict on the causes of its failure. Mulholland also remained defiant in the
face of accusations that any issues of competence, let alone malicious intent, played a role in its design and construction.
[Mulholland, 2000: 325-6]

Three and a half decades passed before the conventional wisdom regarding the causes of the St. Francis Dam failure were challenged.
Examining the available forensic evidence, historian Charles Outland concluded in his 1963 book “Man-Made Disaster” that the
Governor’s Commission investigation overlooked important evidence, seriously compromising their conclusions. Contrary to the
official report, Outland pointed to evidence that a massive landslide had occurred in the unstable Palona Schist on the dam’s eastern
abutment, essentially reversing the failure sequence described in the report of record. In 1995 Outland’s conclusions were scientifically
verified and extensively expanded by engineering geologist J. David Rogers. [Outland, 1963; Rogers, 1995]

The passage of time has tended to bolster Mulholland’s defense of his own character, as well as his instincts as an engineer. When
measured against later building methods the dam was structurally deficient in a number of important respects, any one of which
might have led to its eventual failure. However, recent investigators have largely vindicated Mulholland’s approach to the design and
construction of the dam. Rogers in particular concludes that it was designed within the standards and practices of the era in which it
was constructed. [Rogers, 1995: 81-82]
With the benefit of hindsight, a number of engineering decisions made by the bureau could be faulted. These include the planned
foundation excavations of 30 to 35 feet into the canyon floor, as well as the number of uplift relief wells intended to prevent the dam
from becoming buoyant with the saturation of the concrete by the retained reservoir water. Raising the height of the dam twice during
its design and construction, as political necessity dictated, but without increasing the size and depth of its foundation, also contributed
to the dam’s instability. [Rogers, 1995: 28-32]

The implications of geological conditions on the site were also not fully understood by the bureau. Despite Mulholland’s encounter
with the unstable Palona Schist in the canyon ten years earlier, apparently little if any further investigation into the underlying
materials at the dam site took place prior to the dam’s design and construction.

Excavations into the hillsides for the dam’s abutments were not extensive, but once again, were typical by the standards of the
mid-1920s. Measures to control seepage that became accepted practice after the St. Francis Dam failure, including cutoff walls,
internal inspection galleries, grout curtains, and uplift relief wells beneath the dam abutments, were not included in the dam’s design.