CONSTRUCTION IS WELL underway on the new spillway at Table Rock lake in southwest Missouri, US.

The new spillway was required due to the increased probable maximum flood (PMF) levels at the reservoir. The existing 76.2m high dam on the White river supplies water to the Table Rock power plant, operated as a peaking plant to supply power during high demand periods.

The US Army Corps of Engineers (USACE) found that the dam, designed and constructed in the 1950s, could not handle the revised PMF without it overtopping the earthen embankment section of the dam.

The process of studying the new PMF and its implications has been ongoing since the late 1980’s. In addition to expanding the service spillway, several options such as raising the dam, fixed crest spillway, and building emergency spillways around the dam were also considered.

The ongoing project included the excavation and construction of a new length of earthen embankment, completed in September of 2000, and a US$43.4M contract to Granite Construction Company of Watsonville, California, to construct an auxiliary spillway. Completion of the project is expected in 2004 at a total cost of approximately US$60M.