Indian Valley Dam Radial Gates Evaluation

Abstract Only - This paper presents a case study of Indian Valley Dam radial gates. The paper covers findings from the gates inspection and review of design documents, analysis of the radial gates based on data collected, and design of retrofit to strengthen the gates. Because of the recent failure of similar radial gates at Folsom Dam in California, the California Department of Water Resources, Division of Safety of Dams (DSOD) was promoted to mandate dam owners throughout the state to provide analyses of all radial gates in their jurisdiction. This paper focuses mainly on the findings from the inspection and gates dynamic analyses, and presents the repair solution adopted for the two radial gates. Other issues associated with the radial gates, i.e. trunnions conditions and lubrication, hoisting system performance and maintenance will be briefly discussed.
The gates are approximately 28 feet wide by 25 feet high. Steel arm column trusses support steel horizontal cross members which support steel t-beam girders to which a 3/8" thick steel skin plate is attached. The analyses performed included both static and seismic loading of the gates using finite element methods to evaluate existing capacity of the gates. Because these gates have a float option which could pose failure potential by vibration loading, and additional vibratory analysis was performed to address this specific issue. The results of these analyses had shown that the high ground motions calculated at the dam crest would over stress the gates and consequently, the gates would not meet the adequate safety requirements.
The design of the gate retrofit was implemented taking into consideration site specific issues. These repair issues included heavy metals contained in the paint on the existing gates, welding consideration, especially in light of new information on welding quality resulting form failures in the Northridge Earthquake and gate lift chains, lift motor and trunnion bearing condition. These issues were resolved and presented to both the Federal Energy Regulatory Commission (FERC) and DSOD for approval in the fall of 1996.
Repairs were begun immediately following approval of the design. Modifications were completed in February 1997.