In building the dock the inner row of anchor piles was driven first, followed by each outer row in order until the face of the pier was reached. After the piles were all driven, the sheeting was placed in position and the concrete set.
The proportions of concrete mixture for the sub aqueous work was 1 :3 :5, cement, sand, and broken stone respectively. For the super-aqueous work the concrete mixture was 1 :3:6. High-grade Portland cement, clean sharp sand, and clean stone were used in the concrete mixture, which has a remarkably permanent look and has stood every test to which it has been subjected.
Galveston Sea-Wall. At an ultimate cost of about $4,000,000, the city of Galveston, Texas, has protected itself permanently against the re. currence of disastrous overflows due to such hur ricanes from the Gulf as that of September, 1900, which destroyed a great part of the city, with the loss of hundreds of lives. The work included the erection of over four miles of sea-wall (Plate 32) along the water-front, already built, and the ultimate raising of the grade of the entire city.
In the latter part of July, 1909, the thorough sufficiency of the sea-wall as a protection to the city was demonstrated by the severest of all practical tests—that of actual exposure to a storm approaching in severity that which caused such lamentable loss of life and property in 1900. Notwithstanding the fact that the re cent storm caused $2,000,000 damages along the Gulf coast, with a loss of a score of lives, its effect at Galveston was practically nothing. For twenty hours the foot of the sea-wall was com pletely inundated, but only trifling damage was done to buildings in the area of protection, and not a single life was lost.
The county sea-wall is 3.5 miles long, and the gov ernment wall .87 mile, making a total length of 4.37 miles. The total cost of the county and government wall was $2,091,000. In the construction of the wall, the contractors first drove, at 4 foot intervals, four rows of round piling 40 feet long; and next, just within the out side row of round piling, there was driven a row of Wakefield sheet piling 24 feet long, forming a solid wall 1 foot thick, extending downward from the base of the wall throughout its entire length to prevent the under mining action of the waves. After the piles had been driven, a track was set up over them, and a concrete mixer followed up the pile-drivers, casting a layer of concrete over the piling tops, and, passing over the ground a second time, cast a second layer, the top of which was so finished as to form a key slot base over which the wall itself was later cast. Following up the
concrete mixer, as it formed the base, was a huge der rick, which took from the cars on the tracks along the course of the sea wall, huge granite boulders, which were placed to the seaward of the foundation, a depth of 3 feet and a width of 27 feet, forming an apron riprap designed to keep the waves from cutting away sand from the front of the wall.
The wall itself was formed by large moulds, which were set up over the foundation. These moulds were 16 feet wide at the base, being same width as foundation, and 16 feet high, curving to a 5-foot width at the top. They were about 40 feet long, and the sections of the wall were cast alternately; that is, one section would be cast, then a space left and another section cast, and so on until three or four sections would be sufficiently hardened so that the moulds could be removed and the intervening space filled in. As the moulds were filled, there were inserted reinforcing rods of steel inches by inches by 10 feet, having at each end a 4-inch washer. These reinforcing rods, placed at 2-foot inter vals, were so set as to bind the narrower top of the wall to the broad substantial base.
In the construction of the county wall, which is about five-sixths of the total length, there were used 5,200 carloads of crushed granite, 1,800 carloads of sand, 1,000 carloads of cement, 1,200 carloads of round piling, 400 carloads of sheet piling, 3,700 carloads of riprap, and five carloads of reinforcing rods, making a total of 13,305 carloads of material. The weight per linear foot of the sea-wall, with its foundation and riprap, is 40,000 pounds. If the round piles, 22,289 in number, were placed end to end, they would reach 175 miles, or supply sufficient pil ing for a railroad trestle 10 miles long. The sheet piling would lay a floor 1 inch thick and 24 feet wide for 26 miles, or would make a plank walk 2 feet wide, 312 miles long. If the 2,134,176 cubic feet of granite boulders which comprise the riprap, were placed in a pile 100 feet square at the base, it would make a gigantic monument 215 feet high.