COST OF PNEUMATIO FOUNDATIONS. Of course, the cost will vary with the depth, the character of the soil, the size of the caisson, etc.
Table 68, page 448, gives the details of the cost of the pneumatic caissons of the bridge across the Missouri River near Blair, Neb. The caissons (Fig. 92, page 432) were 54 feet long, 24 feet wide, and 17 feet high. In the two shore piers, No. I and IV of the table, the caissons were surmounted by cribs 20 feet high; but in the channel piers, the masonry rested directly upon the roof of the caisson. The work was done, in 1882-83, by the bridge company's men under the direction of the engineer.
Table 69, page 449, gives the details of the cost of the pneumatic foundation of the Baltimore and Ohio Railway Bridge over the Susquehanna River at Havre de Grace, Md., built in 1884 (§ 870-71).
Table 70, page 450, gives the details of the cost of the pneumatic foundations on the Brooklyn side of the Williamsburg Bridge across the East River, New York City, built in 1896-98. Each caisson is 63 by 79 ft., and each supports four of the eight legs of the steel tower. The south caisson is 39 ft. high, and the north one 53 ft. The south caisson was sunk 86 ft. below mean high water, and the north 107.5 ft. For the schedule of wages and working hours, see the last paragraph of ˘ 896.
Table 71, page 452, shows the cost of the foundations for a large pivot pier and of the two rest piers for a 240 ft. single-track railroad bridge. The work was done by a contractor working on a percentage basis, and the values given are the actual costs to the contractor. The material penetrated was a very uni form bed of fine sand. The pressure men received $3.50 per day.
The foundations for the channel piers of the bridge over the Missouri at Plattsmouth, Neb., built in 1879-80, cost as follows: One foundation, consisting of a caisson 50 ft. long, 20 ft. wide, and 15.5 ft. high, surmounted by a crib 14.15 ft. high, sunk through 13 ft. of water and 20 ft. of soil, cost $19.29 per cubic yard of net volume. Another, consisting of a caisson 50 ft. long, 20 ft. wide, and 15.5 ft. high, surmounted by a crib 36.25 ft. high, sunk through 10 ft. of water and 44 ft. of soil, cost $14.45 per cubic yard of net volume.4 _ _ _ _ Pneumatic Piles. In 1869-72, thirteen cylinders were sunk by the plenum-pneumatic process for the piers of a bridge over the Schuylkill River at South Street, Philadelphia. There were three
piers, one of which was a pivot pier. There were two cylinders, 8 feet in diameter and 82 feet long, sunk through 22 feet of water and 30 feet of "sand and tough compact mud intermingled with bowlders"; two cylinders, 8 feet in diameter and 57 feet long, sunk through 22 feet of water and 5 feet of soil as above; one cylinder, 6 feet in diameter and 64 feet long, sunk through 22 feet of water and 18 feet of soil as above; and 8 columns, 4 feet in diameter and aggregating 507 feet, sunk through 22 feet of water and 18 feet of soil as above. A 10-foot section of the 8-foot cylinder weighed 14,600 pounds, of the 6-foot, 10,800 pounds, and of the 4-foot, 6,800 pounds. The cylinders rested upon bed-rock, and were bolted to it. The actual cost to the contractor, exclusive of tools and machinery, was as in Table 72.
following t is interesting as show ing the cost of pneumatic work in Europe: "At Moulins, cast-iron cylinders, 8 feet 23 inches in diameter, with a filling of concrete and sunk 33 feet below water into marl, cost $62.94 per lineal foot, or $29.71 for the iron work, and 133.23 for sinking and concrete. At Argenteuil, with cylinders 11 feet 10 inches in diameter, the sinking alone cost $42.12 per lineal foot [nearly $10 per cubic yard], where a cylinder was sunk 533 feet in three hundred and ninety hours. [The total cost of this foundation was $34.09 per cubic yard, Table 73, page 457:] At Orival, where a cylinder was sunk 49 feet in twenty days, the cost of sinking was $36.83 per lineal foot. At Bordeaux, with the same-sized cylinders, a gang of eight men conducted. the sinking of one cylinder, and usually 34 cubic yards were excavated every twenty-four hours. The greatest depth reached was 551 feet below the ground, and 71 feet below high water. In the regular course of working, a cylinder was sunk in from nine to fifteen days, and the whole operation, including preparations and filling with concrete, occupied on the average 25 days. One cylinder, or a half pier, cost on the average $11,298.40, of which $1,461 was for sinking. M. Morandie re esti mates the total cost of a cylinder sunk like those at Argenteuil, to a depth of 50 feet, at $7,012.80.