Twin Lakes Dam Emergency Spillway

Twin Lakes Dam – Upper & Lower Twin Lakes Emergency Spillway Design (1998 to 2002)

As a result of the 1986 storm event and the 1997 rain on snow event, which reportedly caused water levels in the lakes to crest each dam, the California Department of Water Resources (DWR) required an evaluation of each dam to verify whether they were adequately sized. RCI was contracted by the water rights owners to conduct hydrologic and hydraulic analyses within the contributing watershed, as well as to prepare Improvement plans for review and approval by the DWR, Forest Service and other responsible agencies. Based on the analyses, it was concluded that the existing dams, built in the late 1800’s, were adequately sized and that expanding the capacity of the emergency spillway would accommodate the required freeboard during a probable maximum precipitation (PMP) event.

Additional work involved in this project included design of the emergency spillway, design of a fish ladder into Upper Twin Lake, slope stabilization and surveying.