The largest rock fill dam in the United States

The Metropolitan Water District of Southern California (MWD) supplies water to some 16 million people in a semi-arid region. Most of this water is imported. Some of the supply lines cross over the San Andreas fault, one of the most notorious and active faults in the U.S. There was a serious need for emergency water in case normal supplies should be interrupted. To fill that need, MWD had to find a reservoir site on the west side of the San Andreas fault, west of the mountains. Because of the distinctive nature of the location, it was necessary to construct a huge bath tub by building a dam at each end of a valley, requiring some 115 million cubic yards (88 million cu.m) of embankment fill. Total material moved was about 150 million cy. In effect, two large-scale surface mining operations were under way simultaneously. The $2.2 billion project is now known as the Diamond Valley Lake Project (formerly called Eastside Reservoir). Because of space limitations, this paper will be limited to those topics which are expected to be of primary, interest to explosives engineers, principally related to large-scale rock fill production. There is not sufficient space to discuss the many diverse geotechnical questions related to site selection, geological and geophysical field testing, laboratory testing and design considerations.