Niagara Falls 100.000-Hp. Development

Niagara Falls 100,000 Hp. Development [27 <-//'->! k-//' -> Section under 3r^ St. Bridge FIG. 36—TYPICAL CANAL CROSS-SECTIONS tion in the canal was a much more difficult task than that of the river. It was all in hard tough limestone, and the mean velocity of the water was 6 ft. per sec. which gave a surface velocity of 10 ft. per sec. when dredges and scows were in place. Eight bridges span the canal which vary from 6 to 15 ft. above the water surface. The drilling and blasting in such a severe current presented many difficulties, but was accom- plished from a drill boat which was developed for this work. Canal Drill Boats The canal drill boat is equipped with five tripod drills operated by a crew of 12 to 15 men. Each drill has one runner and helper. The drill-boat bow is divided into 12 spaces 4 ft. apart and the boat moves back on ranges 4 ft. apart, making the spacing of the holes 4 x 4 ft. and they are drilled 3 ft. below finished grade. The drill steel is li in. diameter and from 20 to 26 ft. long, depending on the depth of the water, with li- to 24-in. bits. The steel drill rods are protected from the current by a main guide barrel of different lengths so as to keep it at least 3 to 4 ft. above the rock. The main guide barrel is 6 in. in diameter and has a 3-in. slit opening from the top to the bottom so that the steel drill rods may be pulled into place. At the bottom of this main guide barrel is a lj-in. ring band to which a cable with a chain fastening is attached to the upstream end of the boat so as to keep the main guide barrel in a vertical position against the strong current. In order to protect the drill rods down to the top of the rock, a 4-in. diameter pipe and a 2i-in. diameter pipe, one 6 ft. long and the other, or bottom piece, 5 ft. long, are made to telescope one another. This telescopic pipe is inserted into the main guide barrel and dropped to the bottom by a chain. There is a J-in. round rivet stopper about 3 in. long which projects out from the side of the telescopic barrel about 6 in. down from the top and as the stopper slides down the slit in the main guide barrel it is stopped by the H-in. round cable band at the bottom of the main guide barrel which holds the telescopic barrel in place and which is lengthened or shortened by the telescopic action and weight of the pipe. The drill rods were put into place by hand. They are first run about half-way out from the end of the boat and pulled back into the main guide barrel through the slit opening by two men and dropped to the top of the rock. As each two feet are drilled it is replaced by a longér drill rod. In blasting a 2-in. tin tube 20 ft. long is run down to the top of the hole through the guide pipe which keeps it from bending or breaking. The sticks of dynamite are put down the tube by a sectional lowering stick, the exploder stick being in the center of the charge which has the two wires attached and extend to the boat up the tube. Before the charge is fired the telescopic barrel is pulled up into the main guide barrel by the chain and let stand, also the tin tube is removed. The charge is set off by a battery and one hole is fired at a time. The kind of explosives used is 60 per cent Dupont and averages about 1 to li lb. per uc. yd. The ordinary l|-yd. dipper dredge was used for dredging between the bridges. The dredging under the bridges was accomplished by two dipper dredges with extremely low cranes, one having a i-yd. and the other a 2-yd. dipper. These dredges were developed par- ticularly for this work on the canal and have given very satisfactory results. One is shown in operation in one of the views. The rock excavated from the canal was placed in steel skip boxes on board scows and floated down the canal under the control of a strong tug to the crusher plant at the canal basin where the rock was unloaded by derricks and crushed. From this point the rock was shipped by train and truck. The drill boat and dredges built for this canal work were developed by R. R. Coddington, General Super- intendent, from his many years’ experience on this class of excavation. The contractor for the excavation in the river and canal is the Great Lakes Dredge & Dock Co. Basin Excavation The old canal basin which connected the canal with the inlet to Station No. 3 was 70 ft. wide and approx- imately 18 ft. deep. As the water for Station No. 3 Extension is taken from this basin, it was necessary to increase the carrying capacity of this basin which was done by increasing the width by excavating on the east side to a width of 117 ft. at the upstream end of the forebay inlet and gradually narrowing down to the old width of 70 ft. near the inlet to old Station No. 3 A curve of 143 ft. radius tangent to the north line of the canal and to this new basin line has made a very- good entrance to the basin. With this enlargement of the basin the mean velocity of the water will be 4.5 ft. per second. The top of the limestone rock lies about 8 ft. below the earth surface and about 2 ft. above the water sur- face in the basin. The earth was excavated with a FIG. 37—ICE BOOMS IN ACTION ON NIAGARA RIVER, MARCH, 1920