Log of drilling at San Carlos dam site in 1913-Continued. Material. Sand, gravel, and bowlders. Broken sandstone. Broken sandstone. Soft sandstone. Sand and gravel. Quartzite, broken near bottom. Shaley sandstone. Soft sandstone. Quartzite. Shaley sandstone. Broken sandstone. Sand, gravel, and bowlders. Sandstone and quartzite. Sand, gravel, and bowlders. Sandstone and quartzite. Sand, gravel, and bowlders. Hard sandstone. Quartzite. Sandstone. Log of drilling at San Carlos dam site in 1913-Continued. NOTE. The sandstone being quartzitic of varying hardness, there was no definite rule available to the driller for distinguishing between it and the quartzite, hence in case of the harder rocks the two terms were used to some extent interchangeably. The term "broken sandstone" does not mean separated rocks, but presence of such incipient seams as would result in partings of the core while drilling. As a result of such partings with oblique fracture, the wedge-shaped fragments, driven down by their own weight and by the downward rushing water, would become locked. in the core barrel, thereby grinding themselves and the core beneath. Thus frequent removal was required in hard rock; but in softer rock the grinding was often allowed to continue, since progress of work was more desired than additional length of core, since the character of rock was fully known, not only from the cores recovered and the sludge, but also from the outcroppings of the same dipping strata visible in the side walls upstream. The softer sandstones had about the hardness of a grindstone, and as much as 10 feet per eight-hour day was drilled in them. As much as 13 feet was drilled in 8 hours in the soft limestone at the lower dam site. In the 44 holes drilled, the aggregate amount of drilling through sand, gravel, and bowlders was 891.2 feet. The total amount of diamond drilling through bowlders was 77.2 feet and in bedrock 582.6 feet. The amount of core saved was 343.1 feet, or 59 per cent. In sinking through bowlders, 449 charges of dynamite were fired, ranging from one-half stick to 15 sticks each. The drilling was by hand power with "Bravo" drill No. 1546, made by Sullivan Machinery Co., of Chicago. The 16 diamonds used weighed 35 carats in the beginning and 255 carats at the close of the work. The cores, 18 inches diameter, are arranged in their proper order in marked compartments of trays in boxes, locked, and now stored at the San Carlos Agency. The record books and the markings on boxes and cores, read together, will give the holes and depths from which the cores were obtained. The work throughout was in charge of Mr. W. E. Jones. 31679°-H. Doc. 791, 63-2—6 D. E. HUGHES. |