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photographs of rock cores, field notes regarding the rock cores, or any sort of office sketch or
drawings mentioning rock cores or samples were ever produced during the Coroner’s Inquest, or
in any of the dozen reports of investigation following the dam failure.
Records preserved the LADWP Archives suggest that 10 shallow borings were made in
the channel of San Francisquito Creek to probe the depth of the channel gravels (Fig. 3). These
were drilled in two parallel lines, along the dam’s axis, three being 4 m deep and the remaining
seven being 8 m deep. These are the same holes utilized as uplift relief wells beneath the
upstream third of the main dam. The sloping abutments and wing dike were not explored by
anything more than open trenches at the time of construction and were bereft of any uplift relief.

FOUNDATION EXCAVATIONS AND KEYWAYS

During his initial testimony BWWS Senior Office Engineer W.W. Hurlbut stated that he and his
staff brought “all of the blueprints” they have of the St. Francis Dam to the Coroner’s Inquest.
When asked “Was there any record kept of the position of bedrock before it was excavated
into?” he replied “No, there is not.” He was then asked “There is no record to show how far you
went into bedrock?” and he answered “No, no record to show that. There is the actual condition
of the foundation – bedrock was cleaned and excavated into.” The only positions recorded were
the rock-concrete interfaces, not the depth of cover excavated.
J. E. Shankland testified that the deepest point of excavation beneath the main portion of
the dam approached a maximum depth of 9 m in the cofferdam trench, but “shallower preceding
downstream.” He estimates the depth of abutment excavations to have been about 3.6 to 4.3 m,
after sluicing off loose materials with water hoses. He recalled excavating a cutoff trench about
one meter deep and wide on the right abutment, which was “feathered to zero, upstream.” In
addition, the steam shovel excavated a shear keyway for the dike section, which was about 4.3 m
wide. On the left abutment Shankland thought his crews only excavated about 1.8 m into the
schist, encountering “hard material,” as determined by resistance to “pick and shovel.”

ALLOWANCE FOR UPLIFT RELIEF

A series of detailed questions were posed to W.W. Hurlbut and Edgar A. Bayley, the BWWS
office engineers whom were credited with having designed Mulholland [Hollywood] Dam and
St. Francis Dam. These questions reveal much about how both dams were designed based on
accepted theories of gravity dam design published before 1922, and the various assumptions
BWWS office engineers and that Chief Engineer William Mulholland made in regards to design
decisions.
When queried about any design accommodation for hydraulic uplift on the Hollywood
[Mulholland] Dam, Bayley stated: “Mr. Mulholland also said there was another matter, the
matter of uplift. Engineering authorities, best men, have various ways of handling the uplift.
One way is a system of drain pipes near the upper toe, another is by gallery inspection, gallery
with upright pipes. All are considered as practical ways of taking care of the uplift. It is a matter
of opinion among the best authorities.”
W.W. Hurlbut was then questioned about the “records of the location of the drainage

system of the dam,” which he said were prepared by Chief Surveyor Harold Hemborg. When
asked if the uplift relief wells extended up the sloping abutments, he responded in the negative.
Several more inquiries were made about limiting “upthrust due to hydrostatic pressure on each

World Environmental and Water Resources Congress 2017