By Edward C. Jones, Gas Engineer
for San Francisco Gas & Electric Co.
Delivered before the Pacific Coast Gas Association
To see the happy faces and evidences of hope and faith in San Francisco today, one is compelled to look down toward the Bay over the ruins of the once beautiful city to realize that on April 18, 1906, at 5:13 a.m., San Francisco, the city we love so well, was visited by an earthquake and fire unprecedented in history.
The brave builders of the new city have long ago ceased to speak of the natural calamity, the earthquake, and in speaking of the sad days following April 18th, they are referred to as after the "fire." It is therefore with some hesitation and regret that the writer is compelled to describe the physical effect on gas property due to the earthquake.
Immediately before the calamity, the San Francisco Gas and Electric Co. was supplying the city from four sources. Carburetted water gas was manufactured and distributed from the North Beach Station [at the corner of Bay and Fillmore Streets], supplying the north and west ends of the city.
The plant, known as the Independent, at the Potrero [on the corner of Twenty-Second and Georgia Streets] was also sending out carburetted water gas in small quantity, while a new 4,000,000-foot crude oil gas set at the Potrero, and the new gas works at Martin Station [in Daly City], which was also provided with a 4,000,000-foot oil gas set, had begun to deliver small quantities of crude oil water gas into the city.
The water gas works at North Beach [in the Marina District] were very badly damaged by the earthquake and were well out of the fire limits.
The Holder Station and storehouse at Fifth and Tehama Streets, were destroyed by fire, while the earthquake affects at the Potrero and Martin stations were peculiar, but so lacking in severity that these stations remained in commission, and the fires were not drawn from the oil gas generators.
Within ten minutes after the first shock of earthquake, the writer was on the way to the North Beach Station, with the purpose of completely shutting off the gas supply from the city as soon as possible, and at this time it is proper and a pleasure to state that every man upon whose shoulders rested responsibility was faithfully at his post, and without waiting for orders had each done the right thing to preserve and protect life and property.
The gas had been shut off at the inlet and outlet of the holders at the works of the Pacific Gas Improvement Co. The gas in storage holder No. 3, with a capacity of 700,000 cubic feet was thereby saved, this holder being but slightly damaged, but storage holders Nos. 1 and 2, with a capacity of 325,000 cubic feet each, were so badly damaged that the gas escaped.
At the North Beach Station the gas was shut off at the inlet of the meter, and the valves were closed at the inlet of the 2,000,000-foot storage holder.
The writer arrived on the ground at this time and found that the 24- inch outlet connections of this holder were broken off between the holder and the outlet valves, so that all attempts to seal the drip pots of the holder by siphoning water from the holder tank did not succeed in saving any of the gas in the holder, which grounded on the wooden framework.
The outlet valves of this holder were closed, however, to prevent the gas from the Potrero Station from backing down through the city and escaping at this point.
The valves an the inlets and outlets of the two 600,000 cubic feet storage holders at Fifth and Tehama streets were closed immediately after the quake.
After the valves at the North Beach Station had been closed, the writer went to the Potrero gas works and closed the valves between the Independent plant and the city, made a hurried test of the twelve- inch steel high-pressure pipeline between Martin Station and the Potrero and finding it tight, shut the valves on this line, and at 7:27 a.m. the valve at the Potrero Station, which were the only remaining outlets for gas into the city mains, were closed, and a bulletin posted, noting the time and reason for shutting the gas off from the city.
Previously to this, the pressure from the Potrero works into the city had been reduced to three inches.
At this time the fire was raging south of Market Street, and had not made great headway, so that the early shutting off of the gas supply prevented the addition of fuel to the flames.
The fact that the gas was shut off in the city was immediately reported to the mayor. With a fire raging in the downtown district, which was eventually to destroy a large portion of the City, it was not then generally known that the city water supply had been cut off by the earthquake, and the only thoughts in the minds of the employees of the San Francisco Gas and Electric Co. was to quickly repair the broken mains and resume the manufacture and distribution of gas.
On this same Wednesday, the eighteenth of April, the street-main gang commenced repairs on the 24-inch trunk-line main at the junction of Van Ness Avenue and Vallejo Street where the street had settled 24 inches, breaking the main, and the pipe was pulled apart 18 inches.
During Wednesday, Thursday, and Friday, the repairs to the mains continued, and the two oil gas plants at Potrero and Martin Stations were repaired ready for use.
During these days there was no means of procuring food unless by standing in the bread line for regular rations as they were distributed. It therefore became necessary to detail men to stand in the bread line, and obtain enough food to keep the street-main gangs fed.
The men worked with a will, apparently forgetting their personal losses, and, in some instances, great sorrows.
Meanwhile, the fire continued to burn the city until it reached Twentieth Street on the west from Dolores to Mission, zigzagging to Fourteenth Street, thence to Townsend, then around the Bay to Van Ness Avenue, burning practically everything east of Van Ness Avenue from the Bay to Market Street.
Beginning at seven o'clock Wednesday morning there were successive explosions in the feeding mains connecting the Potrero and North Beach Stations.
On the thirty-inch main, running from Potrero works on Kentucky [now Third Street], Mariposa, Potrero Avenue, Tenth, Market, and Fell, to Van Ness Avenue. and thence along Van Ness to Broadway, there were twenty-one explosions. In nearly every case the explosion took place at a line drip or cross, where the main was weakest, and the earth around the main was thrown up, leaving openings of various sizes up to twelve foot wide and thirty feet long, and on the line of the twenty-four inch feeding main connecting the two stations there were as many as forty breaks due to explosions.
At other points plugs were blown out of crosses and tees, and in no instance was the lead joint disturbed, and the cast-iron end of the plug was cut cleanly out of the cylinder, leaving the cylinder of the plug firmly held in the socket by the lead joint. Nearly all of the explosions occurred after the gas had been shut off of the city mains, and fortunately these explosions did no damage to life or property.
[This statement is not supported by eyewitness accounts which detail the injury to dozens, if not scores, of refugees from exploding gas mains on those major streets used by them for evacuation from the South-of- Market area. -- G.H.]The cause of the explosions seems veiled in mystery, but the writer firmly believes that they may be accounted for as follows:
The topography of San Francisco is well known, the city having been built on a number of hills, some reaching as high as 400 feet above tide- water. The large feeding mains for bringing gas into the city cross through one of the valleys at a low point from north to south. These mains, as well as those tributary to them, were broken by the shock of the earthquake.
Nearly all the chimneys in the city were destroyed by the earthquake, thus making it either impossible or dangerous to build any fires in the houses. In fact, one of the first orders issued after the earthquake was that no fires should be lighted on any premises. This, of course, did not apply to gas stoves, and as gas for fuel was very popular in San Francisco, there were thousands of gas stoves remaining in the unburned district.
It Is well known that many of these stoves, for days after the gas had been shut off from the city, were getting their supply of gas through the acceleration of pressure due to the rise from the valleys to the hill tops, with the result that air found its way into the feeding mains in the valleys, forming an explosive mixture, which was probably ignited from some of these gas stoves, the wave of explosion passing through the explosive mixture, until it found gas and air in sufficient quantities to explode and break the main.
These explosions, in every instance, must have been ignited at a considerable distance, and without the knowledge of the one who caused the mischief.
The fire burned until Sunday morning, April 22nd. During all this time the work on the street mains was progressing, and as it became evident that the fire would finally reach Van Ness Avenue, it was decided to divide the distribution system of the city east and west of Franklin Street, cutting out every portion of the burnt district, and using the thirty-inch feeding main from the Potrero through Van Ness Avenue as a feeding main for that portion of the city lying west of Franklin Street.
Before the fire there were four systems of street mains known as the San Francisco Gas and Electric Co., the Pacific Gas Improvement Co., the Equitable Gas Co., and the Independent Light and Power Co. These systems were tied together, and the only one provided with valves for isolating it from the others was the Independent Light and Power Co. It was decided to use this system, as far as it reached, to supply gas to the unburned district, and all the valves between this system and the others were tightly closed.
On Sunday morning a large force of men began work at the street intersections on Franklin Street, cutting mains tributary to the Franklin Street main on the east side of the crosses, and plugging them with iron plugs. The west end of the mains leading from the burnt district were plugged with wooden plugs. This work was continued completely around the burnt district, and it may be imagined how much thought, care and prospecting was necessary in order not to overlook a single connection, as one connecting pipe of any size would have fed gas back from the unburned district into the burnt district, where the mains had been badly shattered and had not been repaired, with disastrous results.
While this work was progressing, the thirty-inch feeding main was being repaired.
Not a foundry in San Francisco was running, and it was impossible to obtain thirty-inch sleeves. Few of the large machine shops were spared, but the Risdon Iron Works placed their plant at our disposal and began the turning out of thirty-inch steel sleeves with steel band shrunk on the ends. These were used to repair breaks as a substitute for cast-iron sleeves.
The repairs of the street mains were carried on in all parts of the unburned district and the feeding mains by different gangs of men.
During all this time the different gangs of men were being fed at cooking camps located at the Potrero gas works, North Beach gas works, and the holder station at Fifth and Tehama Streets. The number of men fed at these camps averaged over five hundred. The food was good and the cooking excellent.
Among the obstacles to be overcome in repairing the feeding mains, and some of the larger distributing mains was the removal of water from the pipes where the mains of the Spring Valley Water Company had broken in proximity to a break in the gas main, thus filling large districts with water and sand. In some places the mains were so filled with water that it backed up to the meters, filling them also.
One of the most disagreeable drawback in repairing the thirty-inch main was the removal of dead animals, horses. etc., that were dumped into the trenches opened by the explosions and covered with sand. These were convenient ready-made burial places and when the men opened up the trenches it was impossible to work until fires had been built and the animals incinerated.
Nine days after the fire the street mains in the unburned district and the thirty-inch feeding main had been repaired ready for gas, but as there was no water in the city mains it was deemed best by the city authorities not to turn gas into the mains. This was postponed until May 7th, when gas was turned into the thirty-inch main at the Potrero Station at 9:47 a.m., and air was purged from this main at Van Ness and Broadway, some four miles away.
After the pressure had been turned on to the thirty-inch trunk line, the larger mains of the Independent system, reaching through the Mission and Western Addition, were successively purged of air. This work was performed by using large openings to blow through, and employing a pail of soapsuds and a rubber bag for taking samples of the mixture from the main at short intervals, testing it by lighting the bubbles until the air was entirely displaced by gas.
The gas used for purging was of exceptionally high candle-power, as an element of safety. This work was all performed without the slightest accident, which is remarkable when one considers that out of a total of 566 miles of street mains in use before the fire, about 400 miles were repaired and filled with gas ready for the resumption of gas supply.
In every street in the unburned district there were crude brick ovens constructed in front of the houses for cooking the food; Some of these consisted merely of a number of red bricks laid up dry, with an improvised grate across the top; while others were more elaborate, and some people had moved their kitchen ranges into the street and surrounded them with wooden or galvanized-iron huts, made of three sides and a slanting roof. Most of these street kitchens were immediately over the gas mains in the street outside the curb line.
Here was a problem without precedent. The company was confronted with grave danger of accidents and possible responsibility. The earthquake had moved some buildings and shaken all. House piping had been twisted and broken, chandeliers and brackets wore shaken down, and others were hanging by nipples that were sheared off at the drop ells and tees.
The following short resume of earthquake effects may be of interest: The earthquake movement was apparently from north to south. This was easily demonstrated by the fact that book cases and china closets placed east and west were almost Invariably tipped over, or their contents thrown out; while those placed north and south were in most cases undisturbed. Gas mains in the streets running east and west were broken and drawn apart, while the street mains in streets running north and south were crushed together and telescoped, or else raised out of the ground in inverted V's. This rule applied generally with but few exceptions.
Someone has suggested that if pipes, either water or gas, were laid on solid pile foundations in filled ground that they would be immune from earthquake damage. On Jackson Street between Drumm and Davis streets, which is made land, the street main was laid on a line of piles which went to hard pan. The piles were not purposely driven to sustain the pipe, but happened to be on the line of the main when it was laid. This pipe broke over the center of each pile, nine in number, and was not broken in the made ground, where it was unsupported.
During the latter part of the first shock there was a rotating motion which had the effect of twisting gas holders out of their guide frames.
The foreman of the North Beach Station was looking at the 2,000,000- foot storage holder, and described it as follows:
"On going to the window I looked at the storage holder which was vibrating like an inverted pendulum, and waves of water were coming over the wall of the tank. The relief holder was similarly affected with water and tar coming over the tank wall. The shrubbery in the garden was whipping as though by a strong wind."
These two holders were heavily framed with latticed girders, and did not leave their guides by the rotating movement of the earthquake.
The storage holder at the Pacific Gas Improvement Company's works (on Townsend Street near Third St.) were twisted around 2 feet from the guide rails, while at the Martin Station the 1,500,000-foot storage holder was twisted 5 feet on the lower section, 8 feet on the middle section, and 12 feet on the upper section. At this plant, the 4,000,000-foot generator was moved bodily 2.5 inches to the south. All connections were of steel, and no joints were broken.
A barn at the North Beach Station, corner of Laguna and Bay streets, was resting upon wooden uprights about 15 inches high. These uprights were tipped over and the barn moved the length of the uprights toward the south: that is, after the quake it stood 16 inches on the sidewalk.
The buildings at the different plants did not suffer according to their relative strength. Some brick buildings of comparatively poor construction were unharmed. Other buildings of great strength with heavy footings on good foundations, were shaken to the ground, particularly those running east and west,. while buildings of the same or less strength with foundations not so good, but running in a direction north and south. were but little damaged.
In one instance the walls of the building seemed so thick and strong that the rigidity of the work brought about its destruction. The movement of the walls of the building lagged behind the movement of the earthquake, and the discord of movement throw down the walls.
The amount of damage to gas property seemed to depend more upon location than upon the character of the construction or foundation. Where an earthquake shock will move redwood trees bodily six or eight feet, or open city streets in cracks two or three feet wide, no artificial work of whatever character can be expected to stand.
It was the intention of the writer to present to you the names of those hardworking, faithful men, who did the best work during the restoration of gas supply to the city, and there were many, from the general superintendent down through the ranks, who were untiring and uncomplaining in their efforts during those dark hours, but to do entire justice would require that each and every one in the Company's service should be mentioned by name, as they were all best, and each seemed more zealous than the other.
At this point, Mr. Barr of the Gas Association asked Mr. Jones what effect the earthquake had on the big holder that he spoke of [at the North Beach Station]. Jones replied:
"When the shock of the earthquake came we felt pretty sure about the holder tank, but when I visited the works I found the yard around the tank had settled from two to three feet. It had gone down around the tank like a cuff around a wrist, leaving the tank in its original position without having settled out of level. The columns of the guide frame were plumb, after all of this twisting motion. There was probably a motion of at least eight feet on top of the guide frame, in addition to a rotation of something like six or eight feet. The holder tank showed a small crack, which was repaired."
Return to the 1906 Earthquake Exhibit.