Over the past few weeks  since my first commentary for ENR, based on new information, my ideas have evolved about how the California Dept. of Water Resources should fix the Oroville Dam. In addition to rebuilding the existing main spillway, the department should design a second one.

A second spillway would have its own gate control structure, northwest of the existing control structure.

A second spillway should also have its own gate control structure, northwest of the existing control structure.

The first reason is that a new spillway is needed to augment the existing spillway. Of course, anti-cavitation features should be incorporated into the new design. The new spillway chute would have an alignment almost parallel with the existing spillway, a short distance to the northwest. A portion of the emergency spillway would be demolished to make way for the new gate control structure, and a new approach channel would be excavated.

Just as contractors are completing a $900-million auxiliary spillway at Folsom Dam, near Sacramento, Oroville Dam also should have a second spillway. In fact, all modern dams have two spillways to provide needed redundancy and safety. With the new spillway at Oroville, it would be unlikely that the emergency spillway would ever be used again.

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