The blasting contractor sounds a warning siren prior to detonation. The flat area at the base of the shadow has been drilled with 200 holes that are 48 feet deep and 9 7/8 inches in diameter. Each hole is filled with 1000 lbs of explosives. It takes 1/2 pound of ammonia nitrate fixed with #2 deisel to loosen one-ton of rock. This particular blast cost $45,000 and loosened about 300,000 yards.