the excavation, and material of the river bed banked around outside to hold it in position. The foundation piles were then sunk by water jets inside of the crib.
For the sinking of these piles in the piers the second exceptional piece of equipment was provided, consisting of a pile driver of which the leads were 122 ft. high above the water, and built so as to overhang in front of the barge upon which it was supported about 22 ft. The lowest portion of this overhanging part was about 15 ft. above the water, so that this overhang made it possible to drive all of the piles in a pier from one side of the crib and at any stage of the water. This pile driver was mounted on a wooden scow 32 by 100 ft., 7 ft. deep. In addition to a No. 2 Vulcan Steam Hammer, the driver was equipped with two 4 ins. diameter jet pipes, 110 ft. long, connected by flexible hoses to the pumps. Water was supplied to the jets by two 12 ins. x 18 ins. x 10 ins. compound duplex pumps, each having a capacity of 1,000 gallons per minute. One four-drum hoisting engine and one two—drum hoisting engine supplied the power for handling the equipment and were all furnished steam from an 800-horsepower boiler. A pile would be set in place on the river bed and the jets discharging water with nozzle pressure of from 100 to 150 pounds per square inch played at its point. The jets thus bored a hole into which the pile slid down with the help of the steam hammer. It was an ordinary experience for one of these long piles to be sunk entirely to place within ten minutes after being placed in the leads and as many as 25 piles were driven in one day.
After the piles had been driven, the sand, gravel and other material washed up inside the crib by the driving was removed down to the bottom of the base and the base was filled by depositing concrete under water, through a tremie, up to within a couple of feet of the pile cut-ofl'. When this concrete had thoroughly set the crib was pumped out, the piles sawed off and the remainder of the concrete for the base placed in the open. Wooden forms for the shafts of the piers of usual character were then built up to above water level and filled with concrete. The one-section cofi'erdam was then lifted 011', to be used on a succeeding pier, and the remainder of the shaft forms built up and concreted. The river bed surrounding the pier could then be properly leveled up and adequate amounts of large rip-rap stone placed about the pier. This difficult foundation work was carried out by Mr. C. F. Swigcrt of Portland, under his personal direction.
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