St. Francis Dam - Prelude To Disaster

Prelude To Disaster

Water began to fill the reservoir on March 1, 1926. It rose steadily and uneventfully, other than several temperature and contraction cracks which appeared in the dam and some minor seepage under the abutments. Mulholland and his assistant, Harvey Van Norman, inspected the cracks and leaks and judged them to be within expectation for a concrete dam the size of the St. Francis. At the beginning of April of that year, 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, although they were not entirely successful, and water continued to permeate through the face of the dam. A two-inch pipe was laid from the fault line down to the dam keeper's home and the seepage it collected was used by him 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 ten feet of the spillway, and during most of the month of May the water level was within three feet of overflowing. It is significant to note that 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 is 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 does show that the dam was an exceptionally dry structure.

On May 27 the problems in the Owens Valley escalated again with the dynamiting of a large section of the Los Angeles Aqueduct. A second incident a few days later destroyed another large section. The near full reservoir behind the St. Francis dam was the only source of water from the north and withdrawals began immediately. The Daily Record of High Water Elevations of the St. Francis Dam shows that between May 27 and June 30 alone, between 7000 and 8000 acre-feet were used. Through June and July the Owens Valley fight continued, as did the interruptions in the flow from the aqueduct. This in turn continued the withdrawals from the reservoir.

In early August, the Owens Valley conflict was at its height when suddenly the Inyo County Bank closed the doors of all their branches. The owners, Wilfred and Mark Watterson, who had not only been Inyo County’s financial leaders but also who had organized the valley residents into a unified opposition, were not only bankrupt, they had been indicted for embezzlement. The attacks on the aqueduct ceased, and in the face of the collapse of both resistance and the Owens Valley economy, the city sponsored a series of repair and maintenance programs for aqueduct facilities that stimulated local employment.

Once again the St. Francis reservoir level rose. The level rose steadily for the next six months until in early February 1928, when the water level was brought to within one foot of the spillway. On March 7, 1928, the reservoir was three inches below the spillway crest and, having reached full capacity, Mulholland ordered that no more water be turned into the St. Francis.

During the morning of March 12, while conducting his usual inspection of the dam, the dam keeper discovered a new leak in the west abutment. Concerned that the muddy color of the runoff he observed could indicate the water was eroding the foundation of the dam, he immediately alerted Mulholland. After arriving, both Mulholland and Van Norman began inspecting the area of the leak. Van Norman found the source and by following the runoff determined that the muddy appearance of the water was not from the leak itself, but came from where the water contacted loose soil from a newly cut access road. Mulholland felt that some corrective measures were needed, although they could be done at some time in the future. Both Mulholland and Van Norman were convinced that the new leak was not dangerous and that the dam was safe.