Floodpath

by Jon Wilkman

  The evidence gathered—geological surveys, aerial photography, triangulation measurements, the size and location of dam fragments, and data like the Stevens Gauge record—were added to the testimony of experts and eyewitnesses to establish an analytical foundation for an understanding of the failure of the St. Francis Dam.

  The goal of the Coroner’s Inquest was to arrive at a verdict that determined what and who were responsible for the hundreds of deaths caused by the collapse of the St. Francis Dam. But as the jury continued to listen to testimony and weighed evidence, other investigations reached conclusions of their own.

  The Inquest was prominently covered in the daily press, but the California Governor’s Commission worked in private. They had not been convened to establish personal guilt, but the results of their investigation could change laws as well as offer technical explanations. Like William Mulholland when he built the St. Francis Dam, Governor C.C. Young was in a hurry.

  The Stevens Gauge Chart, showing the apparent slow decline and abrupt drop in the level of the reservoir before the failure (Author’s collection)

  On Monday, March 19, three days before the Coroner’s jury was gaveled to order, members of the California Governor’s Commission met for the first time in Los Angeles. They interviewed William Mulholland and requested engineering and design information needed for their deliberations. On the twentieth they spent a day in San Francisquito Canyon, where a survey team measured the dam site and drillers extracted samples of concrete and the abutment rocks. On the twenty-first they gathered in room 810 of the Sun Finance Building in downtown Los Angeles and held further discussions with Mulholland, joined by engineers from Ventura County.

  On the twenty-second, Commission members returned to the ruins to locate and examine fragments of the dam. By Friday, they were ready to begin writing their report, aided by additional information supplied by Harvey Van Norman and other BWWS and BPL engineers, including a detailed timeline of the disaster compiled from notes in the BPL dispatcher’s log book, eyewitness accounts, and field investigations. Later, a summary was sent to Bureau of Power and Light Chief Ezra Scattergood “so we may have a permanent record.”6 DWP’s so-called Scattergood Memorandum became a primary source for future investigators who were without the ability or sometimes the interest to determine exactly what happened during the first hours of confusion that followed the collapse.

  On Saturday, March 24, the State Commissioners reviewed test results of St. Francis Dam concrete and samples of red conglomerate taken from the west abutment. By Sunday at five P.M., their eighteen-page report was finished. Graphs and annotated photographs would be added later. On Monday, the out-of-town members headed home. The entire investigation took less than a week.

  The details of the Governor’s Commission findings would not be released to the public until April 10, but results were available to the Coroner’s Inquest jury and contributed to their deliberations. To begin, the Governor’s investigating engineers attempted to allay public anxiety about modern dam technology. The report offered assurances that arched gravity dams are “generally accepted by engineers all over the world as a conservative design.”7 As for the strength of concrete, it was “much beyond any stresses to which it could be subjected under normal conditions.” Although Mulholland had not included predetermined contraction joints, the Commission didn’t consider this a contributing factor to the collapse. An earthquake didn’t cause the failure either.

  The report was confident that “There can be no question that such a dam properly built upon a firm and unyielding foundation … may properly be deemed among the most durable of man-made structures.” Then came a big “but.” “Unfortunately, in this case,” the State Inquiry continued, “the foundation under the entire dam left very much to be desired.”8

  The red conglomerate on the west abutment, near the San Francisquito earthquake fault line, was described as an especially weak area. The commissioners concluded that hydraulic piping (water seeping through the conglomerate) likely undermined the St. Francis Dam on the west side and initiated the failure. The theory was advanced that over time the saturated conglomerate softened until it was no longer strong enough to resist the weight of nearly fifty-one million tons of water.

  According to the report, when the dam burst, the power of the flood broke the west side of the concrete wall into fragments and washed them downstream. Escaping water crossed the base of the dam and undercut the downstream foundation of the opposite abutment. The east side of the dam, weak and without support from the west, collapsed, causing a series of landslides that unleashed the full force of the flood. Within minutes, both sides of the St. Francis Dam were destroyed. Only the center section, the Tombstone, was left standing. Some argued that the monolith’s survival was a testament to the strength of the concrete. Others noted ruefully that it was the only section where Mulholland used drainage wells, meant to keep the foundation dry and fixed in place.

  The conclusions of the Governor’s Commission were not the first or the last to be completed before the Coroner’s Inquest delivered a verdict. Paralleling the State Investigation, the Los Angeles City Council had commissioned a national-level inquiry chaired by Dr. Elwood Mead, the Chief of the U.S. Bureau of Reclamation in Washington, D.C.

  On March 25, with the Los Angeles Inquest in progress, Mead’s five-man panel was announced. It included representatives of the American Society of Civil Engineers and the former Chief Engineer of the U.S. Army Corps of Engineers. One of the commission members, Lansing H. Beach, was a Los Angeles–based consulting engineer who supervised the planning of the Elephant Butte Dam, mentioned by DWP engineers as a model for the Mulholland and St. Francis Dams. After six days of study, including meetings with Mulholland and other DWP staff and a quick trip to the dam site, the prestigious engineers finished their work.

  Drawing upon much of the same technical data used by the California Governor’s Commission, the Mead Committee agreed that the saturation of the west abutment conglomerate near the fault line “made [the] failure of the dam inevitable.” The engineers concluded: “Based on the fact that the foundation on that side [the west] was poorest, and confirmed by the fact that the portions of concrete which form this part of the dam have completely disappeared from the site, and immense broken blocks are found far downstream, while with one exception the broken portions on the east side are more nearly in place and occupy positions which indicate that this part of the dam failed by undermining rather than [the] thrust of impounded water.”9 In other words, the failure began with the weakened foundation of the west side abutment, which released a floodwave that caused a landslide that brought down the east side of the dam.

  As for the possibility of an earthquake, Carnegie Institute seismologist Harry Wood reported more than twenty quakes “of local character” between January 1 and March 13, 1928, but none close enough to affect the St. Francis Dam site. He concluded, “It is a wholly safe conclusion that the failure of the St. Francis Dam can not be attributed to seismic action.”10

  One intriguing piece of information mentioned by Mead investigators involved the triangulation measurements. The surveyor’s calculations seemed to indicate the top of the Tombstone moved 0.7 feet downstream, and the entire monolith had twisted slightly. In the final report this was considered a result of the tremendous forces released during the collapse, not a causal factor.11

  In addition to reports from the Governor’s and Mead investigations, Los Angeles District Attorney Asa Keyes had his own “fact-finding commission,” chaired by Los Angeles structural engineer Edward L. Mayberry. Mayberry was considered an authority on reinforced concrete buildings, including well-known movie theaters he built in downtown Los Angeles. He was joined by two local engineers, Walter Clark and Charles Leeds, and two geologists, Allan E. Sedgwick and Louis Z. Johnson.

  When the twenty-two-page Keyes Report was completed, despite the D.A.’s tough and sometimes derisive questioning of William Mulholland during the Inquest, the fact
-finding commission concluded that the Chief’s dam had been built “in accord with accepted practices,” and the concrete quality was “acceptable.” The culprit again was a poor foundation, especially the now-notorious red conglomerate, exposed on the west abutment. The fact finders concluded: “The progressive movement of water from the reservoir through the conglomerate carried the clay and some of the sand and iron oxide with it, leaving a spongy, cellular structure incapable of carrying great loads.” Case closed.

  Not so fast. Just as it looked as if a consensus was locked in place and the Coroner’s Inquest was heading toward a verdict that could lead to a trial that could put William Mulholland behind bars, an unexpected witness was sworn in. Frank Rieber, the son of the respected Dean of Arts and Sciences at the University of California, Los Angeles, was born on March 12, exactly thirty-eight years before the collapse of the St. Francis Dam. The independent-minded Rieber was known as a prankster during his years at the University of California, Berkeley, where he graduated with a Bachelor of Science degree in 1915. Later in life, he would make notable contributions to petroleum exploration technology.

  In 1928, Rieber’s professional expertise was geophysics and the study of the earth’s crust, not dams, but he informed the jury that he had spent the past two years working extensively with dynamite on a project to study geological strata associated with oil in California’s San Joaquin Valley. “I realize that this is not a theory contest,” the Berkeley-based geophysicist told the Coroner, jury, and assorted attorneys.12 Admitting that he wasn’t inflexible in his conclusions, he proceeded to present an analytical approach that challenged the conclusions of every prestigious board and commission before him, and many that followed.

  The collapse of the St. Francis Dam, Rieber declared, began on the east abutment, not the west. Enormous landslides didn’t finish the failure, he said, they started it, and more to the point, the massive land movements could have been initiated by a dynamite attack. There are no reports of audible groans from engineers in the hearing room, but DWP critics were hardly pleased by the resuscitation of the dynamite theory.

  When it was revealed that Rieber had been recruited by the BWWS to investigate the failure, pointed questions were raised about his credibility, as well as his credentials. The DWP had helped him build a scale model of the St. Francis Dam with colored lines drawn on the downstream face outlining the original positions of known fragments, or blocks. This visual aid was an irresistible lure to picture-hungry news photographers and an effective means to attract public attention to Rieber’s new point of view.

  Despite unconcealed skepticism from questioners, the Berkeley geophysicist, known to his friends as a “master of repartee,”13 seemed unfazed as he pointed out weaknesses in the west-side thesis.14 To begin, scour lines indicated that the high-water mark of the flood on the west abutment was about forty feet below the top of the dam, leaving a construction road on the hillside untouched.15 If the west side failed first, it was logical that the scour lines should be higher. In fact, the scour lines on the east side were higher, curving down as the flood rushed into the canyon, a sign that the first rush of the flood, when the reservoir was still full, had started there.

  Although a majority of downstream residents of San Francisquito Canyon didn’t survive the floodwaters, Rieber pointed out that the experience of the few who did presented a formidable obstacle to the west-abutment theory. None of them recalled a preflood before the collapse. A west-abutment failure depended on increasing seepage, which he calculated would have reached enough volume to cover the downstream floor of San Francisquito Canyon. If this had been true, Rieber argued, why wasn’t it noticed by Katherine Spann, her companion Helmer Steen, and motorcyclist Ace Hopewell, the three late-night travelers who passed the site only a short time before the failure?

  As further support for his opinion, Rieber examined the Stevens Gauge chart with a microscope and said this closer look didn’t show the degree of decline in the reservoir level reported by others. More evidence came from the metal “stilling pipe” attached to the gauge. It was broken off below a connecting strap, thirty feet from the bottom, and bent toward the east; evidently the result of water from the west rushing into the gap left by the collapsed east end of the dam.

  Additional support for Rieber’s hypothesis came from triangulation measurements. The Mead Commission reported that these before-and-after studies indicated the Tombstone had moved slightly downstream and twisted clockwise toward the east. Rieber reasoned that this was only possible if the west side of the structure was still standing, able to lean against the remaining unsupported section of the dam and push it eastward.

  To further demonstrate the role of the dam’s movement in the collapse, Rieber asked jurors (and reporters with pencils poised) to imagine a man blocking a doorway that was too narrow to allow him to pass. Put the man on roller skates, however, and give him a slight shove from below, and his feet would slide out from under him and open the way. The engineer said this same principle applied to the St Francis Dam as it slid forward and collapsed after the east-side landslide destabilized the structure.

  The broken Stevens Gauge stilling pipe, bent to the east, as viewed from upstream (Author’s collection)

  All this was very interesting, but Rieber needed to explain the most self-evident clues in support of a west-side collapse. Many fragments from that side were located far downstream, while large blocks remained heaped below the east abutment. This would seem to indicate the force of the water escaping from the west side was greater and emerged sooner. In response, Rieber suggested that the enormous quantity of schist from the east-abutment landslide created temporary barriers that slowed the rush of water, leaving the fragments at the foot of the Tombstone.

  When the displaced eastern hillside fell into the reservoir, it contained close to 550,000 cubic yards16 of rock and soil, more than all the concrete used to build the dam. This collapse produced a powerful wave, Rieber told the Inquest jurors, that surged across the man-made lake and brought down the west side. Referring to a drawing of the floodpath, he pointed out fragments downstream from both abutments, found in close proximity to one another, noting that in some instances pieces from the west were found over pieces from the east, an indication they arrived afterward.

  As for the role of dynamite, Rieber contended it wouldn’t take a large quantity to bring down the dam, especially if the barrier was “shot” from both abutments. Since no unexpected bodies were found in the rubble, he guessed the dynamiters already paid for their crime, killed when they set off the explosions. Although the Berkeley geophysicist didn’t think the mysterious note and map that made headlines just as the Inquest began were important to his theory, he admitted that his research had been assisted by documents analyst J. Clark Sellers, who evaluated the controversial evidence. Rieber also revealed that Sellers helped with photographs taken at the dam site and played the role of “devil’s advocate,” challenging his arguments in preparation for cross-examination at the Inquest.17

  If most dam engineers at the time, and probably a majority of the Inquest jurors, doubted the east-abutment theory, they considered the dynamite explanation little more than a DWP attempt to shift blame to unknown Owens Valley militants. Since the earliest days of the Owens River Aqueduct, L.A.’s semi-independent Water and Power Department exercised formidable political and public relations skills, and DWP representatives were especially effective working behind the scenes.

  Beneath the public surface of the Coroner’s Inquest a struggle that included business interests and politicians as well as engineers was under way to affect the outcome. Even as Bill Mulholland accepted sole responsibility for the St. Francis Dam failure, he remained a proud man who wouldn’t tolerate a rush to judgment without a fight, especially if he believed he was wrongly accused. During his career the Chief had attracted lifelong enemies, but he and the DWP had influential friends, and alternative theories about the St. Francis Dam failure could provide reinforc
ement for the defense.

  Knowing this, Coroner Nance and D.A.s Keyes and Dennison were not in a receptive mood when bespectacled sixty-year-old Stanford University ichthyologist Edwin Chapin (E.C.) Starks refused to dismiss the idea that dead fish found in ponds downstream from the dam had been killed by an explosion.18 Starks admitted he wasn’t an explosives expert but that he sometimes used underwater dynamite to quickly gather specimens for his research. Nance was in his element when he questioned Starks about the results of fish autopsies, but he couldn’t shake the ichthyologist’s willingness to entertain a dynamite-driven postmortem, even though he acknowledged it could be asphyxiation caused by silt, as most other experts had concluded.

  In the hearing room, an atmosphere of frustration and impatience hadn’t changed when fifty-eight-year-old Zattu Cushing, an explosives expert with experience with the U.S. Army and the DuPont Company, was sworn in. Cushing had worked on the Owens River Aqueduct and the investigation of the Times bombing. He told the jury he decided to travel from his home in El Paso when he read news stories reporting that samples of Mulholland’s concrete crumbled easily. “I told my wife that Mr. Mulholland never made any such concrete as that, and that the only thing that would crumble concrete would be a shock by explosives.”19