by John Dvorak
The plan was to build a watertight, oval-shaped wall of concrete, 30 feet thick, large enough that it could enclose a football field, which would extend from the 60-foot depth of the sea floor north of Fort Point up to and extending 15 feet above the level of high tide. Then the seawater would be pumped out and—the interior of the oval structure being then free of water—workers would begin the difficult task of digging down, first through mud, then through serpentine, to a solid foundation. Lawson originally thought the workers would have to remove about 25 feet of serpentine to find competent rock, but his estimate proved to be nearly a factor of two too little.
It took almost a year to build the oval structure, to remove the seawater, and to excavate through 40 feet of serpentine. The foundation for the south pier was now at a depth of 100 feet below sea level. At that level, engineering tests showed that the serpentine should be able to support the hundreds of pounds per square inch of pressure the steel bridge would exert on the rock. Workers had started to use concrete to fill the massive hole when a new objection was raised—from a highly vocal source—about the building of the Golden Gate Bridge.
Bailey Willis, head of the geology department at Stanford University, certainly had the credentials to raise an objection. Unlike Strauss, who Willis claimed was an engineer who knew nothing of geology, and Lawson, who Willis said was a geologist who did not understand engineering, the Stanford professor could claim expertise in both fields. He had graduated with dual degrees in geology and civil engineering from Columbia University and had done practical work in both fields. Included in his long list of accomplishments was a year-long geological expedition he had led through northern China, and another year in Argentina, where he advised the government on the routing and construction of railroads in the Andes. In 1922, relying on the work of Lawson and many others, he had produced the first map that showed active faults in California, declaring that earthquakes along those features were “as certain as thunderstorms in New York in early summer.” And if one examined his map, which was published by the Seismological Society of America, of which both he and Lawson had once been president, there was an active fault that passed directly beneath where the south pier was under construction.
Willis first went public with his concern in late 1933, saying that the south pier, as it was then positioned, sat “on a ‘pudding stone’ of serpentine.” Here the rock was so weak, Willis went on, that “even vibrations from the San Andreas Fault might cause the pier site and its 200,000-pound load to slide into the channel.” Then there was the matter, as he also pointed out, of an active fault, a possible branch of the San Andreas, or so Willis suggested, running directly under the pier.
As if to illustrate his concern, soon after Willis had made these statements, trouble of a similar kind was being reported on the other side of San Francisco, where another massive bridge was under construction.
The Golden Gate Bridge and the Bay Bridge were being built simultaneously. But the Bay Bridge posed fewer engineering problems.
Its design consisted of two parts: One part ran from Oakland to Yerba Buena Island in the center of the bay, and the other part from Yerba Buena Island to a landing in San Francisco. Here tidal currents were slower than through the Golden Gate, and the impact of storms and other severe weather less intense. The floor of the bay was nearly flat and shallow. Concrete caissons were manufactured and sunk along a line that the bridge would run. Atop the concrete caissons, the steel piers would be built, upon which the weight of the bridge would rest.
But on January 25, 1934, a problem was reported at caisson W-6, the first one west of Yerba Buena Island. Surveys showed that the base of the caisson had slipped.
A diver was sent down. In the blackness of the bottom, the diver felt his way around the caisson, deciding that one edge was hung up on a huge boulder. He returned to the surface, dove again with a packet of dynamite, planted it where he thought it would do the most good, then resurfaced. The dynamite was exploded. Repeated surveys have shown the caisson has never shifted again.
But the incident at the Bay Bridge directed attention to the south pier of the Golden Gate Bridge. There were still opponents to completion of the bridge, notably from Southern Pacific Company, which owned the ferry lines that crossed the bay, and from lumber companies in northern California that saw their political power falling if the bridge was finished and they were no longer isolated from most of the rest of the state. So Willis’s objections started to gain support.
Willis issued a letter of concern about the stability of the south pier, asking that the concrete that had already been poured be removed and that the foundation be dug down another 250 feet. Strauss asked Lawson for a response. In a private letter to Strauss, Lawson called the objections “pure buncombe,” and in a public statement he charged Willis with being a “professional alarmist.” He disputed Willis’s claim that an active fault ran under the south pier. He said the green serpentine would be a firm foundation if workers excavated to a deep enough level. Willis responded by publishing a long letter, covering two full pages in the newspaper The Argonaut, that called for all work to halt at the bridge site. And then, as if on cue, two weeks after the letter appeared, the largest jolt to occur along the San Andreas Fault since 1906 struck near San Francisco at midday on October 2, 1934.
From the reports of the thousands of people who felt the earthquake, it was centered near Mussel Rock and consisted of two distinct shocks, separated by about ten minutes. Dishes and windows rattled in San Francisco. The only reported injury in the city was to a Miss Grace Williams, who was stepping down from a curb at Geary and Powell and fell and hurt her arm. A convention of 400 delegates of the American Federation of Labor, always a feisty crowd, was meeting in San Francisco at the time, and the delegates were in heated debates when the first shock hit. The convention hall suddenly went silent. After a minute or so, the delegates resumed shouting at each other—when the second shaking happened. During the ensuing silence, someone offered a motion to adjourn for lunch. It was passed by a unanimous vote.
The steel tower built over the north pier, the top 746 feet above sea level making the tower 200 feet taller than the Washington Monument, was almost completed when the earthquake struck, and a dozen or so men were working on the tower when it began to sway. One worker was Alfred “Frenchy” Gales, who had been a bus driver before becoming a bridge builder. According to him, during the swaying, the top of the tower moved 16 feet each way. He watched as “guys were lying on the deck, throwing up and everything.” He decided, as the swaying continued, that if the tower failed he was going to ride the steel all the way to the water.
But the north tower did stand. Strauss, Lawson, and other engineers examined the site the next day, proclaiming the bridge had withstood its first earthquake test.
Still, Willis was not silent. He claimed the serpentine rock exposed at the south pier was only 100 or so feet in thickness, and beneath it was more friable sandstone. In the event of a repeat of what occurred in 1906, the weight of the bridge would cause the base of serpentine rock to shear off the lower sandstone and the whole bridge would collapse into the channel.
Strauss ordered workers on the south pier to continue to fill the oval structure with concrete. He also had several holes outside the oval structure drilled to a depth of 250 feet. Lawson examined the recovered cores, saying it was still serpentine and that it was dense and without fractures. But Willis persisted—and opposition to completing the bridge grew. To silence it, Strauss called on Lawson to stage a performance.
By then, 65 feet of concrete had been poured, though through the concrete eight inspection wells were still open that extended all the way down to the serpentine base. On December 7, 1934, Lawson made a descent down Well No. 3.
Before the descent he and Russell Cone, an inspecting engineer who would accompany him down, were bolted inside an air lock at the top of Well No. 3 while the air pressure was stepped up
from normal outside atmosphere to 40 pounds per square inch on their bodies. That was to allow them to pass through an air lock partway down the well. Once the air pressure was at the proper level, the two men started down, climbing on ladders attached to the inside of the 4-foot-diameter well. There were electric lights all the way down.
At the bottom, more than 100 feet below sea level, they stood inside a dome-shaped room about the size of a typical living room. The glare of four 50-watt lamps lit the scene. The center of the floor was free of mud and rocky debris and stood about 2 feet higher than the edges. A puddle about 6 feet long and 2 feet wide was near one side of the room. Lawson knelt down and examined the rock. It was compact serpentine, remarkably free of any seams. He hit it with his hammer. As he would later report to Strauss, “It rings like steel.” Then, in words that pleased the chief engineer, Lawson pronounced the serpentine foundation to be “all that could be desired.” In his judgment, it “would support several times the pier load with perfect safety.”
Lawson’s report was given to the press. Bridge construction continued without much controversy, though there was one more seismic test.
On March 8, 1937, according to a press release from the university at Berkeley, an earthquake of “moderate intensity” was felt throughout the Bay Area. It was centered on the Hayward Fault. Sixty chimneys in El Cerrito, north of Berkeley, were damaged. People reported that dishes, glass bottles, and windows were broken elsewhere. It occurred at 2:32 in the morning, so no one was on the bridge. The next day an inspection was made and the bridge was declared by Strauss to be “untouched.”
On May 27, 1937, the Golden Gate Bridge was dedicated and, for the day, open only to pedestrians. At noon the next day, President Franklin Roosevelt pressed a telegraph key in the White House and the bridge was officially open to traffic.
Here it is instructive to examine the history of the reactions of the Golden Gate Bridge and the Bay Bridge to later seismic disturbances in light of their respective “births” at the same time that earthquake science were still in their early infancy.
On Friday, March 22, 1957, shortly before noon, an earthquake hit the Bay Area. It was centered near Daly City, possibly on the San Andreas Fault. According to the San Francisco Chronicle, in the city there was a “twisting, jarring side-rolling motion” that caused skyscrapers to sway visibly. The shaking was enough to cause people to run into the streets, some “sobbing hysterically.” A person who was on the Golden Gate Bridge reported the bridge “undulated as in a fierce gale.” But inspections showed no damage to it or to the bridge on the other side of the bay.
On February 9, 1971, an earthquake occurred north of Los Angeles in the San Fernando Valley. Never before had seismic shaking damaged a modern highway in California. Then, in just 12 seconds, nearly 70 bridges designed to resist earthquakes and thought by their designers to be quake proof were damaged. Seven bridges collapsed or were so badly damaged that they had to be replaced.
No shaking, of course, was felt in northern California, but as a result of the 1971 San Fernando earthquake, the California Department of Transportation enacted new standards for a range of structures, including bridges. And in 1982, retrofit projects were completed on the Golden Gate Bridge and the Bay Bridge to strengthen both bridges should a major earthquake strike nearby. A test of the retrofit came seven years later on October 17, 1989.
Known as the Loma Prieta earthquake because the event originated beneath that peak in the Santa Cruz Mountains, it was the largest seismic event to occur in northern California since 1906. Most people, however, remember it as the World Series earthquake because it occurred just before the start of the third game of the 1989 World Series between the Oakland Athletics and the San Francisco Giants.
Severe damage occurred in the city of Santa Cruz and the surrounding area. There was also a significant amount of damage in San Francisco, especially to buildings with ground-floor garages—so-called “soft” stories—that require open space for cars to turn around and park in. In Oakland, a mile-and-a-half section of a double-decked highway collapsed that was built on mud flats, a soil condition that amplifies seismic motion. Forty-two motorists, most of whom were on the lower level, were crushed when the upper deck fell on the lower one.
The shaking also did damage to the Bay Bridge. The 50-foot spans of roadway on both the upper and lower decks of the Bay Bridge at pier E-9, about halfway between Yerba Buena Island and Oakland, collapsed. At the west end of each span was an expansion joint that the earthquake shaking pulled off a six-inch-wide seat, and at the east end a bolted connection. When the spans were pulled away, they both swung down under gravity, pivoting on the bolted connections, the upper span coming to rest on the lower one. The lower one came to rest on an electrical housing; otherwise, both would probably have swung completely open.
A motorist who was on the bridge at the time of the earthquake saw cars “sliding around like they were on ice.” Bruce Stephan, who was driving with a passenger on the upper deck when the span collapsed, would remember thinking, “I’m going through the bridge and into the bay! … I knew it was death. I didn’t think there was anything that could stop us.”
But there was.
His car stopped inches shy of plunging into the bay, the car wedged in the gap between the collapsed upper deck and split-open lower one. He was looking at water. He clambered out of the wrecked vehicle and pulled his passenger with him. They walked a mile to Yerba Buena Island for medical treatment.
The Golden Gate Bridge had no damage. But engineering studies conducted after the earthquake concluded that major sections of both bridges could have collapsed if the intensity of the shaking had been stronger and the duration longer—that is, if a more powerful earthquake—like the one in 1906—had occurred. In particular, such an event might lift the 320-foot arch over Fort Point on Golden Gate Bridge off its bearing pins, causing the entire arch to collapse. That, according to the study, could lead to a chain reaction and possible “collapse of the main suspended span.” And it could happen in 60 seconds.
The entire two-mile-long east section of the Bay Bridge from Yerba Buena Island to the Oakland landing has now been replaced with a new bridge. It was more cost-effective to retrofit the Golden Gate Bridge than replace it—and the retrofitting, which would eventually cost a billion dollars, was far enough along by April 2006, the 100th anniversary of the great earthquake, that the bridge no longer faces the potential for collapse. Both bridges have also been covered with a network of sensors that will record how the bridges respond to the shaking of future earthquakes.
The Golden Gate Bridge got a minor test of its new seismic safety on June 28, 2010, when a small earthquake occurred along the San Andreas Fault at exactly the spot where the 1906 quake originated. About 2,000 people felt the 2010 event. According to a bridge engineer, the peak acceleration recorded by any of the sensors on the bridge was 0.5 g, that is, equivalent to half the acceleration of gravity. The engineer characterized it as a “fling.” In the 1930s, Chief Engineer Joseph Strauss, using the best information available about ground acceleration during an earthquake—which came from Japan after the disastrous earthquake that devastated Tokyo in 1923—originally designed the Golden Gate Bridge to withstand a peak acceleration of 0.1 g.
The professional disagreements between Lawson and Willis continued after the Golden Gate Bridge was completed, and extended into other topics. It became almost a tradition at scientific meetings that they would disagree and have a shouting match. Whatever position one man took, the other man seemed to take the opposite position automatically.
Fortunately, Willis was wrong about his assessment of the stability of the south pier of the Golden Gate Bridge. He did, however, make an important contribution by reminding Californians that the risk to life and property from earthquakes was, and still is, a continual one. After the 1925 earthquake in Santa Barbara, during which 13 people died and most of downtown was destro
yed leaving only a few buildings along State Street still standing, Willis publicly challenged a number of booster organizations—the All-Year Club of Southern California, the California Development Association, the chambers of commerce of San Diego and San Francisco—that tried to downplay the magnitude of the disaster. His effort did lead to the first building codes in California that required earthquake-resistant construction, adopted initially by the cities of Palo Alto and Santa Barbara. It would take another earthquake, in 1933, before such codes were adopted statewide, and then they were required only of school buildings.
Soon after Willis died in 1949, someone visiting Lawson noticed that the Berkeley professor had placed a photograph of his nemesis over his desk. The visitor asked if the photograph was really of Bailey Willis. Lawson just turned to his visitor and smiled.
On March 11, 1949, Lawson made headlines a final time when it was reported that the 87-year-old now-retired Berkeley professor had fathered a child with his 39-year-old wife. Local newspaper reporters found him at the Oakland hospital where the birth took place and asked how this was possible.
