as much as they would stand, and to load them first with No. 2 powder to within about 4 feet of the top, and then with No. 1 for an additional height of 3 or 4 feet, firing them in large groups, and simultaneously if possible. When this was done the bed-rock was finely broken up over the whole area blasted, a deep depression being left at the center, and the material around the edges piled up to a height of from 3 to 6 feet. Generally the surrounding material was but little broken, so that in most cases the drills could commence work again at a distance of from 8 to 10 feet from the last holes drilled. No tamping other than the water which constantly filled the holes was used, except in a few cases, when snow was rammed into the holes above water level. The estimated total number of cubic yards broken up on the reef is 42,402, though it is probable that this is much less than the true amount, since the average depth to which the rock was broken is assumed as only 12 feet, while in reality it may be, and probably is, much more. The results of the seasons operations are shown in detail in the following tables, and on the accompanying maps, where are given the location of the reefs and bowlders attacked, and the amounts broken up and removed in each case, as well as the cost of each improvement, and of the different kinds of work: Record of rock removed by submerged blasts from the Columbia River below Cascades Canal, Oregon, November 1, 1883, to February 22, 1884. Detailed statement of work on Columbia River below Cascades Canal from November 1, 1883, to February 22, 1884. Holes drilled by steam-drills Pounds of powder used, No. 2. Caps. Cost of labor Cost of powder, fuse, and caps Cost of stores, iron, steel, coal, lumber, &c Cost of tow-boat, actual time employed. Cost of tow-boat for transportation Cost of tow-boat, maintenance and repairs Total cost per cubic yard blasted. |