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In the latter part of December, 1899, the earth in front of and between the power house and bulkhead, and at point E, fig. 5, began to sink and continued to sink until it was determined to remove the earth covering the 9-foot penstocks under the sunken areas, in order to discover the cause. The removal of the earth showed that penstock No. 3 (fig. 5) was buckled, and that at one place it had sunk about 20 inches. A bold stream of water-at least 2 second-feet in amount and 16 feet below the top of the dam-was found when the earth was taken out between the power house and penstock No. 3, and between penstocks Nos. 3 and 4. The stream of water was partly deflected around the north end of the power house and under penstocks Nos. 1 and 2. The water did not rise in the excavation, and it was discharged through some 2-inch pipes at F, fig. 5, 14 feet below the crest of the dam, through two or three other small pipes, and by absorption through the wing wall FC and through the east wall of the power house. Penstock No. 5 was also found buckled at a joint about 35 feet from the bulkhead. The water which caused the settling came from a broken 2-inch pipe tapped into the bottom of penstock No. 5. The break was at an elbow just below the penstock, at a point about 16 feet below the crest of the dam and 40 feet from the south side of the bulkhead masonry.

FLOW OF COLORADO RIVER.

The minimum flow of Colorado River was estimated in 1890 to be 1,000 cubic feet per second; and it was upon this estimate that the engineers based their calculations of the power that would become available by the erection of a dam 60 feet high above low water. With an effective head of 57.5 feet and a machinery efficiency of 80 per cent of the theoretic, for this flow there would be available continuously 5,227 horsepower, and if held back nights and Sundays and used only 60 hours a week, 14,600 horsepower.

After February 10, 1897, the city's plant furnished power for its own water end light system, for the Dam and Suburban Railway, for the Rapid Transit Street Railway, and for various motors in the city. This required, in the opinion of the superintendent of water and lights, an average of about 1,000 horsepower; that is, with a machinery efficiency of 75 per cent, about 200 cubic feet of water per second. During 1897 the lake level was below the crest of the dam eighty-nine days, showing that the supply of water at the forebay was not sufficient to carry the load upon it. In 1898 the water was below the crest one hundred and eighty-six days, and in 1899 it was below two hundred and four days, making a total of four hundred and seventy-seven days during the last three years, or 43 per cent of the time from January 1, 1897, to January 1, 1900.

The maximum flood height occurred on June 7, 1899, when the water level of the lake was 9.8 feet above the crest of the dam, giving