Changing spillway gates without drawing down a reservoir

Not all spillway gates are designed with a stoplog to provide a way of isolating them from the reservoir. This is particularly the case in old facilities, or when the span of the spillway is too large. This can be a major problem for planning maintenance operations, repairs and/or the replacement of spillway gates, especially when concrete walls have difficult shapes relatively small dimensions, where the sealing is complicated. In such cases, repair works or inspections cannot be carried out without partly or totally drawing down the reservoir, which means a very high loss of revenue, or complete shutdown of a powerplant. This paper focuses on modular designs for stoplogs and spillway gates, as well as assembly techniques which can be used on ageing infrastructure in the hydro industry, with emphasis on safety, quality and environmental protection.