A series of pools built like steps to enable fish to ascend a dam or waterfall.A fish ladder was built into the 29-foot-high dam....
City officials proposed using the revenue to cover the cost of removing 620 miles of road, building fish ladders, and other environmental protections.
Dams prevent upstream migration of adult salmon, but this can be overcome to some extent by the construction of fish ladders in which the salmon jump up a long series of waterfalls.