Off-Channel Reservoir Spillway
A reinforced concrete spillway will be constructed on the left (west) abutment of the main dam. The purpose of the spillway is to safely convey storm events, up to the probable maximum flood (PMF), around the main dam embankment. The PMF storm event estimated for Chimney Hollow incorporates recently developed climate change impacts into the estimate to make sure that the dam remains safe into the future. It is a state-of-the-art design to minimize risk of failure in the event of spillway operation. Because Chimney Hollow Reservoir is an off-channel reservoir, and not located on a major river system, the spillway is quite small relative to the size of the main dam. The spillway has a 10-foot-wide chute, approximately 3,800 feet long that contains about 12,000 cubic yards of reinforced concrete, all produced on site.
The majority of the spillway will be constructed below the existing ground surface to keep the spillway on a solid rock foundation and help with the aesthetics of the site.