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World Environmental and Water Resources Congress 2017 386

developed “58 to 60 feet west of the gates” [outlet pipes], and another crack approximately the
same distance on the other side, and one at about the “quarter point” of the main dam. Another
transverse crack formed at the other quarter point (shown in Fig. 5).

Figure 5. Stepped downstream face of the St. Francis Dam, as viewed looking upstream.
Four prominent shrinkage cracks developed, shown in the lower diagram. These were
caulked with oakum on the downstream face and grouted in early 1928 (author’s
collection).

Phillips stated that “these cracks extended all of the way through the dam.” He noted that
th
the apertures of most of the shrinkage cracks were initially between 1/8 and 3/16ths of an inch
at the crest of the dam (Fig. 6). What engineers didn’t understand at the time was that the width
was inconsequential; it was the transverse connectivity with the dam’s upstream face that

impacted internal stability.
Phillips went onto describe how the shrinkage cracks were caulked with oakum; a
mixture of hemp or jute fiber that was often smeared with tar, creosote, or asphalt to caulk seams
in wooden ships and packing pipe joints. He noted that BWWS crews drilled holes into the dam

World Environmental and Water Resources Congress 2017