DANGEROUS DECOMMISSIONED DAMS
Around the world, some 5,000 large dams are now more than 50 years old, and the number and size of the dams reaching their half century is rapidly increasing. The average age of dams in the US is now around 40 years. According to a panel on dam aging at ICOLD’s 1991 Congress, “in the future attention and activity [will] be more and more shifted from the design and construction of new dams to the restoration of the structural and operational safety of existing dams”. Many of these are decommissioned dams.
Dangerous dams, however, are far from purely a problem of the ex–Soviet republics. Between 1977 and 1982 the Corps of Engineers inspected 8,800 non–federal dams in the US, most of them privately–owned, which it classified as “high–hazard” – where a failure could cause significant loss of life. One–third of these dams – 2,900 – were considered to be “unsafe”, primarily because of inadequate spillway capacity. A 1994 survey showed at least 1,800 non–federal dams were still unsafe. The situation is similar for federal dams: in 1987 one–fifth of BuRec’s 275 dams were classified as unsafe, as were one–third of the 554 dams operated by the Corps of Engineers.
An Ontario Hydro study of data from several hundred North American dams shows that on average hydro dam operating costs rise dramatically after around 25–35 years of operation due to the increasing need for repairs. When the cost of maintaining an old dam exceeds the receipts from power sales, its owners must decide either to invest in rehabilitating the dam, or, if the cost of repairs would be prohibitive, to disconnect the dam from the grid and cease producing power.
As discussed, small dams and small dam owners collectively, represent as great a risk to the public as large dams and large dam owners, if not more so.
Preliminary estimates indicate that by 2030, from 2% to 15% of the nation’s electricity could come from water power – including hydro power and marine and hydro kinetic energy sources, such as waves and tides.