Large dam upgrades in North America are squeezing every megawatt out of the grid as efficiently as possible by converting century-old powerhouses and replacing decades-old turbines. Construction is under way at several sites, from Pennsylvania to British Columbia. Earlier this month, PPL Montana began upgrading its Rainbow Dam, a 36-megawatt dam on the Missouri River, six miles northeast of Great Falls, Mont., where 200 workers are under the direction of Chicago’s Walsh Construction. Photo: Courtesy BC Hydro British Columbian utility will boost generating capacity at W.A.C. Bennett Dam by phasing in five replacement turbine units by 2017. PPL Montana says
Arch dams, classically curved monoliths situated in narrow valleys, are not as common as other types of dams, such as embankment dams and gravity dams. ENR takes a look at some of the biggest arch dams in the world, both completed and under construction.