Evaluation of Fish Passage Alternatives at Lock and Dam 3 of the Mississippi River

The Upper Mississippi River has 29 navigation dams that restrict fish movement. Of the 143 native fish species in the river at least 40 are migratory.  Downriver fish passage can occur through the locks, over fixed-crest spillways and through dam gates.  However, upriver migrations are more limited.  Locks do not provide favorable pathways for fish passage.  Upriver fish passage through the dam gates is possible for larger and stronger-swimming fish during limited periods when the gates are raised out of the water.  Most of the time dam gates are in the water, resulting in high current velocities through the gate openings that preclude upriver fish passage.

We are evaluating alternative fish passage features at Lock and Dam 3 on the Mississippi River.  Study alternatives focus on nature-like fishway design.  We are adapting design criteria from similar studies to assess and compare costs and benefits of fish passage improvements.  Preliminary construction costs for the likely preferred alternative are $11.5 million, though the final study will be completed later in 2012.  The likelihood for future construction funding is highly uncertain.  In addition to construction costs and funding sources, a major obstacle to overcome is concern with upriver invasion of Asian carp.