Effects of Spillway Operation on Cavitation Damage to Hugh Keenleyside Dam Spillway

The Hugh Keenleyside Dam (also known as Arrow Dam) is located on the Columbia River, at the outlet of Lower Arrow Lake, 53 km north of the Canada - U.S.A. border. The project has been in operation since October 1968. During the first reservoir drawdown in 1970 cavitation damage to the concrete on the spillway crest near the gate slots was discovered in all four bays. All attempts to repair the eroded concrete with epoxy mixtures and fiber-reinforced concrete in 1973, 1975 and 1977 were unsuccessful. The last repair was carried out in 1977 and approximately 80% of the repair material was found to be eroded during the March 1980 annual inspection. The areal extent of the damage has not changed appreciably since 1980. Between March 1980 and March 1985 there has been an increase in the depth of erosion of 2 to 3 cm in local areas. As the spillway is in regular use for six to eight months each year, this damage is a continuing problem. A study was carried out to determine the source of the cavitation damage and to find a permanent solution to prevent its recurrence. Study results are discussed.