St. Francis Dam

Background

In the early years of Los Angeles, the city's water supply was obtained from the Los Angeles River. This was accomplished by diverting water from the river through a series of ditches called zanjas. At that time, a private water company, the Los Angeles City Water Company, leased the city's waterworks and provided water to the city. Hired in 1878 as a zanjero (ditch tender), William Mulholland proved to be a brilliant employee who, after doing his day's work, would study textbooks on mathematics, hydraulics and geology, thereby teaching himself geology and engineering. Mulholland quickly moved up the ranks of the water company and was promoted to superintendent in 1886.

In 1902, the City of Los Angeles ended its lease with the water company and took control over the city's water supply. The Los Angeles City Council established the Water Department – renamed the Bureau of Water Works and Supply in 1911 – with Mulholland as its superintendent. Mulholland was concurrently named as the Bureau's chief engineer following the organization's name change.

Mulholland achieved great recognition among members of the engineering community when he supervised the design and construction of the Los Angeles Aqueduct, which at the time was the longest aqueduct in the world. It used gravity alone to bring the water 233 miles (375 km) from the Owens Valley to Los Angeles. The project was completed in 1913, on time and under budget, despite several setbacks. Excluding incidents of sabotage by Owens Valley residents during the California Water Wars, the aqueduct has continued to operate well throughout its history and remains in operation today.

Planning and design

It was during the process of building the aqueduct that Mulholland first considered sections of San Francisquito Canyon as a potential dam site. He felt that there should be a reservoir of sufficient size to provide water for Los Angeles for an extended period in the event of a drought or if the aqueduct were damaged by an earthquake. In particular, he favored the area between where the hydroelectric power plants Powerhouses No. 1 and No. 2 were to be built, with what he perceived as favorable topography, a natural narrowing of the canyon downstream of a wide, upstream platform which would allow the creation of a large reservoir area with a minimum possible dam. A large camp had been set up to house the workers near this area, and Mulholland used his spare time becoming familiar with the area's geological features.

In the area where the dam would later be situated, Mulholland found the mid- and upper portion of the western hillside consisted mainly of a reddish-colored conglomerate and sandstone formation that had small veins of gypsum interspersed within it. Below the red conglomerate, down the remaining portion of the western hillside, crossing the canyon floor and up the eastern wall, a drastically different rock composition prevailed. These areas were made up of mica schist that was severely laminated, cross-faulted in many areas, and interspersed with talc. Later, although many geologists disagreed on the exact location of the area of contact between the two formations, a majority opinion placed it at the inactive San Francisquito Fault line. Mulholland ordered exploratory tunnels and shafts excavated into the red conglomerate hillside to determine its characteristics and had water percolation tests performed. The results convinced him that the hill would make a satisfactory abutment for a dam should the need ever arise.

A surprising aspect of the early geologic exploration came later, when the need for a dam arose. Although Mulholland wrote of the unstable nature of the face of schist on the eastern side of the canyon in his annual report to the Board of Public Works in 1911, this fact was either misjudged or ignored by Stanley Dunham, the construction supervisor of the St. Francis Dam. Dunham testified, at the coroner's inquest, that tests which he had ordered yielded results which showed the rock to be hard and of the same nature throughout the entire area which became the eastern abutment. His opinion was that this area was more than suitable for construction of the dam.

The population of Los Angeles had been increasing rapidly. In 1900, the population was slightly more than 100,000. By 1910, it had more than tripled to 320,000, and by 1920 it had reached 576,673. This unexpectedly rapid growth brought a demand for a larger water supply. Between 1920 and 1926, seven smaller reservoirs were built and modifications were made to raise the height of the water bureau's largest of the time, the Lower San Fernando reservoir, by seven feet, but the need for a still-larger reservoir was clear.

Construction and modification

The process of surveying the area and determining the location for the St. Francis Dam began in December 1922. Clearing of the site and construction began without any of the usual fanfare for a municipal project of this nature. The Los Angeles Aqueduct had become the target of frequent sabotage by angry farmers and landowners in the Owens Valley and the city was eager to avoid any repeat of these expensive and time-consuming repairs.

The St. Francis Dam, sometimes referred to as the San Francisquito Dam, was only the second concrete dam to be designed and built by the Bureau of Water Works and Supply. The first was the nearly dimensionally-identical Mulholland Dam, on which construction had begun one year earlier. The design of the St. Francis Dam was in fact an adaptation of the Mulholland Dam, with modifications made so as to suit the site. Most of the design profiles and computation figures of stress factors for the St. Francis Dam came from this adaptation of the plans and formulas which had been used in the constructing of the Mulholland Dam. This work was done by the engineering department within the Bureau of Water Works and Supply.

In describing the shape and type of the St. Francis Dam, the word curved is used although, by today's standards, due to the amount of curve in its radius, the dam would be considered arched, therefore making it of the arch-gravity design. It was not so called because the science of arch-gravity dams was still in its infancy. Little was known in the engineering community about the arch effect, how it worked and how loads were transmitted, other than that it did help with stability and support. As such, the dam was designed without any of the additional benefits given by the arch action, which led to its profile being considered conservative, given its size.

Annually, as did most other city entities, the Bureau of Water Works and Supply and the ancillary departments reported to the Board of Public Service Commissioners on the prior fiscal year's activities. From these it is known that the preliminary studies of the area which became the site of the St. Francis Dam, and topographical surveys for the dam, were completed by June 1923. They called for a dam built to the elevation of 1,825 ft (556 m) above sea level, which is 175 ft (53 m) above the stream bed base. These early calculations for a reservoir created by the dam revealed it would have a capacity of approximately 30,000 acre⋅ft (37,000,000 m3).

Dam instability

Water began to fill the reservoir on March 12, 1926. It rose steadily and rather uneventfully, although several temperature and contraction cracks did appear in the dam, and a minor amount of seepage began to flow from under the abutments. In accord with the protocol for design, which had been established by the Engineering department during construction of the Mulholland Dam, no contraction joints were incorporated. The most notable incidents were two vertical cracks that ran down through the dam from the top; one was approximately 58 feet (18 m) west of the outlet gates and another about the same distance to the east. Mulholland, along with his assistant chief engineer and general manager Harvey Van Norman, inspected the cracks and judged them to be within expectation for a concrete dam the size of the St. Francis.

At the beginning of April, the water level reached the area of the inactive San Francisquito Fault line in the western abutment. Some seepage began almost immediately as the water covered this area. Workers were ordered to seal off the leak, but they were not entirely successful, and water continued to permeate through the face of the dam. A two-inch (5.1 cm) pipe was used to collect this seepage and was laid from the fault line down to the home of the dam keeper, Tony Harnischfeger, which he used for domestic purposes. Water that collected in the drainage pipes under the dam to relieve the hydrostatic uplift pressure was carried off in this manner as well.

In April 1927 the reservoir level was brought to within 10 feet (3 m) of the spillway, and during most of May the water level was within 3 feet (0.91 m) of overflowing. There were no large changes in the amount of the seepage that was collected and, month after month, the pipe flowed about one-third full. This was an insignificant amount for a dam the size of the St. Francis, and on this subject Mulholland said, "Of all the dams I have built and of all the dams I have ever seen, it was the driest dam of its size I ever saw." The seepage data recorded during the 1926–1927 period shows that the dam was an exceptionally dry structure.

On May 27, 1927, the problems in the Owens Valley escalated once again with the dynamiting of a large section of the Los Angeles Aqueduct, part of the California water wars. A second incident took place a few days later, destroying another large section. In the days that followed, several more sections of the aqueduct were dynamited which caused a complete disruption of the flow. The near-full reservoir behind the St. Francis Dam was the only source of water from the north and withdrawals began immediately.

Collapse and flood wave

Two and a half minutes before midnight on March 12, 1928, the St. Francis Dam catastrophically failed.

There were no surviving eyewitnesses to the collapse, but at least five people passed the dam less than an hour before without noticing anything unusual. The last, Ace Hopewell, a carpenter at Powerhouse No. 1, rode his motorcycle past the dam about ten minutes before midnight. At the coroner's inquest, Hopewell testified he had passed Powerhouse No. 2 without seeing anything there or at the dam that caused him concern. He stated at approximately one and one-half miles (2.4 km) upstream he heard, above his motorcycle's engine noise, a rumbling much like the sound of "rocks rolling on the hill." Hopewell stopped, got off his motorcycle and smoked a cigarette while checking the hillsides. The rumbling had begun to fade, and Hopewell assumed the sound was a landslide common to the area. Hopewell finished his cigarette, got back on his motorcycle and left. He was the last person to see the St. Francis Dam intact and survive.

At both of the Bureau of Power and Light's receiving stations in Los Angeles and at the Bureau of Water Works and Supply at Powerhouse No. 1, there was a sharp voltage drop at 11:57:30 p.m. Simultaneously, a transformer at Southern California Edison's (SCE) Saugus substation exploded, a situation investigators later determined was caused by wires up the western hillside of San Francisquito Canyon about ninety feet above the dam's east abutment shorting.

Given the known height of the flood wave, and the fact that within seventy minutes or less after the collapse the reservoir was virtually empty, the failure must have been sudden and complete. Seconds after it began, little of the dam remained standing, other than the center section and wing wall. The main dam, from west of the center section to the wing wall abutment atop the hillside, broke into several large pieces and numerous smaller pieces. All of these were washed downstream as 12.4 billion gallons (47 million m3) of water began surging down San Francisquito Canyon. The largest piece, weighing approximately 10,000 tons (9,000 metric tons) was found about three-quarters of a mile (1.2 km) below the dam site.

Somewhat similarly, the dam portion east of the center section had also broken into several larger and smaller pieces. Unlike the western side, most of these came to rest near the base of the standing section. The largest fragments fell across the lower portion of the standing section, coming to rest partially on its upstream face. Initially, the two remaining sections of the dam remained upright. As the reservoir lowered, water undercut the already undermined eastern portion, which twisted and fell backwards toward the eastern hillside, breaking into three sections.

Investigation

There were at least a dozen investigations into the disaster. With unprecedented speed, eight of these had begun by the weekend following the collapse. Almost all involved investigative panels of prominent engineers and geologists. The more notable of these groups and committees were those sponsored by Governor C. C. Young, headed by A. J. Wiley, the renowned dam engineer and consultant to the U.S. Bureau of Reclamation's Boulder (Hoover) Dam Board; the Los Angeles City Council, which was chaired by the chief of the Reclamation Service, Elwood Mead; Los Angeles County coroner Frank Nance, and Los Angeles County District Attorney Asa Keyes. Others were convened: the Water and Power Commissioners started their own inquiry, as did the Los Angeles County Board of Supervisors, who hired J. B. Lippincott. The Santa Clara River Protective Association employed the geologist and Stanford University professor emeritus, Dr. Bailey Willis, and eminent San Francisco civil engineer and past president of the American Society of Civil Engineers, Carl E. Grunsky. There were still others, such as the state railroad commission and several political entities who only sent investigators or representatives.

Although they were not unanimous on all points, most commissions quickly reached their conclusions. The governor's commission met on March 19 and submitted their 79-page report to the governor on March 24, only eleven days after the collapse. Although this may have been sufficient time to answer what they had been directed to determine, they had been deprived of the sworn testimony at the coroner's inquest, which was scheduled to be convened March 21, the only inquiry that took into consideration factors other than geology and engineering.

The need for immediate answers was understandable, having its roots in the Swing–Johnson Bill in Congress. This bill, which had first been filed in 1922, and failed to be voted on in three successive Congresses, was again before Congress at the time. This bill ultimately provided the funding for constructing the Hoover Dam. Supporters and responsible leaders alike realized the jeopardy in which the bill stood. Although the water and electricity from the project were needed, the idea of the construction of such a massive dam of similar design, which would create a reservoir seven hundred times larger than the St. Francis, did not sit well with many in light of the recent disaster and the devastation. The bill was passed by Congress and signed into law by U.S. President Calvin Coolidge on December 21, 1928.

Aftermath

The center section of the St. Francis Dam, which had become known as "The Tombstone" due to a newspaper reporter's description of it as such, became an attraction for tourists and souvenir hunters. It was toppled with dynamite in May 1929 after the death of a sightseer there who fell from the block, and the remaining blocks were demolished with bulldozers and jackhammers to discourage exploration of the ruins by the public. The wing dike was used by Los Angeles firemen to gain experience in using explosives on building structures.

The dam was not rebuilt, though Bouquet Reservoir in nearby Bouquet Canyon was built in 1934 as a lower-capacity early replacement, with additional capacity added upon the completion of the Castaic Dam decades later in 1973, which holds nine times the capacity impounded by the St. Francis Dam.

The exact number of victims remains unknown. The official death toll in August 1928 was 385, but the remains of victims continued to be discovered every few years until the mid-1950s. Many victims were swept out to sea when the flood reached the Pacific Ocean and were never recovered, while others were washed ashore, some as far south as the Mexican border. The remains of one victim were found deep underground near Newhall in 1992, and other bodies, believed to be victims of the disaster, were found in the late 1970s and 1994. The death toll is currently estimated to be at least 431.

At the coroner's inquest, the leak that Harnischfeger had spotted was cited as evidence that the dam was leaking on the day of the break, and that both Mulholland and the Bureau of Water Works and Supply were aware of it. Mulholland told the jury he had been at the dam the day of the break due to the dam keeper's call, but neither he nor Van Norman had observed anything of concern, nor found any dangerous conditions. Mulholland further testified that leaks in dams, especially of the type and size of the St. Francis, were common. During the inquest Mulholland said, "This inquest is a very painful thing for me to have to attend but it is the occasion of it that is painful. The only ones I envy about this thing are the ones who are dead." In subsequent testimony, after answering a question he added, "Whether it is good or bad, don't blame anyone else, you just fasten it on me. If there was an error in human judgment, I was the human, I won't try to fasten it on anyone else."

Dam safety legislation

In response to the St. Francis Dam disaster, the California legislature created an updated dam safety program and eliminated the municipal exemption. Before this was added, a municipality having its own engineering department was completely exempt from regulation.

On August 14, 1929, the Department of Public Works, under the administrative oversight of the state engineer, which was later assumed by the Division of Safety of Dams, was given authority to review all non-federal dams over 25 feet (7.6 m) high or which could hold more than 50 acre-feet (62,000 m3) of water. The new legislation also allowed the state to employ consultants, as they deemed necessary. Additionally, the state was given full authority to supervise the maintenance and operation of all non-federal dams.

Licensing of civil engineers

Having determined that the unregulated design of construction projects constituted a hazard to the public, the California legislature passed laws to regulate civil engineering and, in 1929, created the state Board of Registration for Civil Engineers (now the Board for Professional Engineers, Land Surveyors, and Geologists).

Analysis

At present, the popular hypothesis is that collapse may have begun with the eastern abutment of the dam giving way, possibly due to a landslide. This scenario, having its roots in the works of Willis and Grunsky, was expanded upon by the author Charles Outland in his 1963 book Man‑Made Disaster: The Story of St. Francis Dam. The material on which the eastern abutment of the dam had been built may itself have been part of an ancient landslide, but this would have been impossible for almost any geologists of the 1920s to detect. Indeed, the site had been inspected twice, at different times, by two of the leading geologists and civil engineers of the day, Grunsky and John C. Branner of Stanford University; neither found fault with the San Francisquito rock.

J. David Rogers, inspired by the work of Outland, investigated the failure and published an extensive scenario, albeit somewhat controversial, of the possible geological and rock mechanic actions which may have led to the dam's failure. He attributed the failure to three major factors: the instability of the ancient landslide material on which the dam was built, the failure to compensate for the additional height added to the dam's design, and the design and construction being overseen by only one person.

A critique of Rogers' historical analysis of the dam's collapse was published in the journal California History in 2004 by historians Norris Hundley Jr. (Professor Emeritus, UCLA) and Donald C. Jackson (Professor, Lafayette College). While accepting most of his geological analysis of the failure, the article makes clearer the differences and deficiencies of the structure built in San Francisquito Canyon and how it fell short of the standards for large-scale concrete gravity dams as practiced by other prominent dam engineers in the 1920s.

Mulholland Dam reinforcement

Shortly after the disaster, many living below Mulholland Dam, which creates the Hollywood Reservoir, feared a similar disaster and began to protest, petitioning the City of Los Angeles to drain the reservoir and remove the dam. A Committee of Engineers & Geologists to Assess Mulholland Dam was appointed to evaluate the dam's safety. An external review panel to evaluate the structure, convened by the State of California, followed in 1930. The same year, the City of Los Angeles Board of Water & Power Commissioners appointed their own Board of Review for the dam. Although the state's panel did not recommend modification of the dam, both panels came to similar conclusions: that the dam lacked what was then considered sufficient uplift relief, which could lead to destabilization, and was unacceptable. Again in 1931, a fourth panel, the Board of Engineers to Evaluate Mulholland Dam, was appointed to assess the structure. As well, an external study group appointed by the Board of Water & Power Commissioners produced a "Geological Report of the Suitability of Foundations". Certain design deficiencies were uncovered in the plans made by the engineering department during the planning phase of the dam. These had to do with the dam's base width in conjunction to its ability to resist uplift and sliding and to withstand earthquake loading.

The decision was made to permanently keep the Hollywood Reservoir drawn down. It was also decided to keep the amount stored in the reservoir to no more than 4,000 acre⋅ft (4,900,000 m3) and to place an enormous amount of earth, 330,000 cu yd (250,000 m3), on the dam's downstream face to increase its resistance against hydraulic uplift and earthquake forces, and to screen it from public view. This work was carried out in 1933 and 1934.

Legacy

The only visible remains of the St. Francis Dam are weathered, broken chunks of gray concrete and the rusted remnants of the handrails that lined the top of the dam and the wing dike. The ruins and the scar from the ancient landslide can be seen from San Francisquito Canyon Road. Large chunks of debris can still be found scattered about the creek bed south of the dam's original site.

The site of the disaster is registered as California Historical Landmark #919. The landmark is located on the grounds of Powerhouse No. 2 and is near San Francisquito Canyon Road. The marker reads:

NO. 919 ST. FRANCIS DAM DISASTER SITE – The 185-foot concrete St. Francis Dam, part of the Los Angeles aqueduct system, stood a mile and a half north of this spot. On March 12, 1928, just before midnight, it collapsed and sent over twelve billion gallons of water roaring down the valley of the Santa Clara River. Over 450 lives were lost in this, one of California's greatest disasters.

San Francisquito Canyon Road sustained heavy storm damage in 2005, and when rebuilt in 2009 it was re-routed away from the original roadbed and the remains of the main section of the dam. The new road is routed through a cut which was made in the hillside on the western edge of the wing dike.

National Monument and National Memorial

The John D. Dingell Jr. Conservation, Management, and Recreation Act, signed March 12, 2019, established the Saint Francis Dam Disaster National Monument and authorized the establishment of the Saint Francis Dam Disaster National Memorial. The sites will be administered by the United States Forest Service within Angeles National Forest to commemorate the collapse of the dam and preserve 353 acres (143 ha) of land for recreation and protection of resources. Access to the Monument will be by foot via Old San Francisquito Canyon Road.

The St. Francis Dam National Memorial Foundation is a non-profit organization, established in 2019, with the goal of raising funds to support the United States Forest Service in building and maintaining the St. Francis Dam Disaster National Memorial and Monument, including the construction of a visitor center and a memorial wall with the names of all the identified victims. A winning memorial design was announced in April 2023.

Documentaries

The rise of Mulholland, Los Angeles' water issues, and the collapse of the dam are dealt with in the 2018 documentary film, Forgotten Tragedy: The Story of The St Francis Dam, by Jesse Cash.

The story of the dam's construction and catastrophic failure is also the subject of the documentary Flood in the Desert, which was first broadcast in May 2022 as part of the American Experience series on PBS.

In popular culture

Numerous fictionalized references are made to Mulholland, the California water wars, the aqueduct and the St. Francis Dam disaster in the 1974 movie Chinatown.

Rock musician Frank Black makes several references to the St. Francis Dam disaster in his songs "St. Francis Dam Disaster" and "Olé Mulholland."

The 2014 young adult novel 100 Sideways Miles by Andrew A. Smith features the current site of the dam disaster as well as some discussion of the historical event.

The 2015 folk song "Lucy on the Line" by Tim Griffin and Maya Bohnhoff commemorates the brave "Hello Girl" telephone operators who, at risk to their lives, kept calling residents down the flood path, warning them to evacuate.