 However, by the early 21st Century, the combined power output of both dams only provided the equivalent of 38% of the electricity needed to operate one paper mill, the Daishowa America mill.Lacking passage for migrating salmon, its construction blocked access by anadromous salmonids to the upper 38 miles (48 km) of mainstem habitat and more than of tributary habitat.The salmon runs that once numbered more than 400,000 adult returns in over of available habitat, now numbered less than 4,000 adult returns on only of available habitat.