The length of this sea wall is 4,400 feet, and the con tract involved the enlargement of 3,670 feet of old levee, the building of 730 feet of new levee, the driving of 4,400 linear feet of steel sheet piling, and the placing of the reinforced concrete.
Work was begun December 1, 1907; and after the enlarged and newly built levee had settled sufficiently, the driving of piling was commenced. The piling was shipped by barge on the Mississippi river, the first lot arriving in March and the second in May. The piles were driven by a drop hammer weighing 2,800 pounds, with which was used a cushion hood which wholly pre vented any battering of the ends. The drop of the hammer was 10 feet, and the average number of blows was eight.
The steel piles were 19 feet long, driven 14 feet into the levee and extending 5 feet above its top. The piling was specified not to be less than % inch thick, to be driven vertically and in straight lines from angle to angle of levee. Twelve-inch 38-pound United States steel sheet piling was chosen as being peculiarly fitted for the work in hand; and 4,476 pieces were driven, weighing in all 1,508 net tons.
The object of the steel piling curtain wall was to prevent seepage into the reservation from the Gulf side, and it was therefore necessary that this wall be made water-tight.
After the piles were driven, the voids in the interlock were filled with grout composed of three parts of sand and one part of cement, the result of which was to make an absolutely impervious structure.
While the soil was practically all silt, several live oak stumps buried underground were encountered, through which the piling was driven without much diffi culty. But one pile-driver was used, and new high rec ords in the driving of sheet piling were made; the mini mum number of piles driven per eight-hour day was 113, and the maximum 281, a record for driving unprece dented in the history of the steel sheet piling industry.
Under ordinary conditions, United States steel sheet piling can usually be made water-tight by wooden pack ing strips driven with the pilings; but in order to avoid the possibility of leakage, the specifications required all piles to be heavily coated with asphaltum pitch, and this coating to be thoroughly dry before the piles were driven.
The five feet of piling which projected above ground was capped with concrete made in blocks 10 feet long. Reinforcement was of plain round steel bars, showing an ultimate strength of 60,000 pounds per square inch, and an elastic limit of not less than one-half the ulti mate strength. Vertical and horizontal reinforcing rods were securely fastened with clamps. The concrete was composed of one part cement, three parts sand, and five parts of gravel or broken stone. The concrete forms were so constructed as to give a perfectly smooth sur face, and no plaster or outside covering was allowed to be applied to the concrete surface after removal of forms.
Concrete Bath Houses. The city of Boston, which maintains a large number of floating wooden bath houses in the harbor, is under heavy expense each year to repair these, as they suffer destruction during the winter months. All the woodwork that can be torn away is usually car ried off; the lead pipe and fittings also disappear. The extensive repairs each year has caused the chairman of the Bath Department to make a close study of reinforced concrete, which mate rial is to be used hereafter in constructing these floating baths, and thus save much of the cost of annual repairs.