Dam 1, a curved concrete gravity dam, constructed 1925-1929, in the 102-square-mile Bull Run watershed near Mount Hood, has a maximum reservoir capacity of 10 billion gallons, making it the primary contributor to the Portland Water System Distribution Area. The spillway gates visible in this photo, added to the dam in 1955, increased the reservoir capacity from the original 8.8 billion gallons to 10 billion gallons.
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