Sly Creek Dam is a dam in Butte County, California. The earthen rockfill dam was completed in 1961 by the local public utility, the South Feather Water and Power Agency, formerly known as the Oroville-Wyandotte Irrigation District. The dam stands 289 feet high and 1,235 feet long at its crest. It impounds Lost Creek for irrigation storage and hydroelectric …Sly Creek Dam is a dam in Butte County, California. The earthen rockfill dam was completed in 1961 by the local public utility, the South Feather Water and Power Agency, formerly known as the Oroville-Wyandotte Irrigation District. The dam stands 289 feet high and 1,235 feet long at its crest. It impounds Lost Creek for irrigation storage and hydroelectric power, along with the smaller Lost Creek Dam immediately downstream.