If you take a rafting trip down the Colorado River through Marble Canyon, which would have been flooded had the dam been built, you will pass by a spot where th

If you take a rafting trip down the Colorado River through Marble Canyon, which would have been flooded had the dam been built, you will pass by a spot where there are a couple holes dug into the side of the canyon. These holes were test holes whose purpose was to determine whether the rock was structurally sound enough to support the dam. It is an eerie feeling to slowly float by them realizing these would have been flooded under hundreds of feet of water had the Army Corps of Engineers been successful. The salvation of Grand Canyon was one of the greatest environmental victories of the 20th century.