This section is from the book "Cyclopedia Of Architecture, Carpentry, And Building", by James C. et al. Also available from Amazon: Cyclopedia Of Architecture, Carpentry And Building.
The first piles driven for the Cambridge (Mass.) conduit of the Charles River dam were on the Cambridge shore. On January 1, 1907, 9,969 piles had been driven in the Boston and Cambridge cofferdams, amounting to 297,000 linear feet. Under the lock, the average length of the piles, after being cut off, was 29 feet; and under the sluices, 31 feet 4 inches. The specifications called for piles to be winter-cut from straight, live trees, not less than 10 inches in diameter at the butt when cut off in the work, and not less than 6 inches in diameter at the small end. The safe load assumed for the lock foundations was 12 tons per pile, and for the sluices 7 tons per pile.
The Engineering News formula was used in determining the bearing power of the piles. The piles under the lock walls were driven very close together; and as a result, many of them rose during the driving of adjacent piles, and it was necessary to redrive these piles.*