One structure that failed the test was the Edwards Dam, which blocked the lower reaches of Maine's Kennebec River for 162 years and which was demolished in June 1999. The Kennebec once was home to virtually every Northeast-dwelling species of anadromous fish--ocean-dwelling fish that come up rivers to spawn-- from sturgeon to salmon. Remnant populations hung on below the dam and are expected to gain steadily —and in some cases dramatically —over the next twenty years.

An important factor in the decision to dismantle the Edwards Dam was the fact that it didn't control floods, irrigate fields, or generate much hydropower. Many dams do, and provide a non-polluting alternative to coal- or nuclear-powered energy. However, they do have serious environmental impacts. Dams disrupt rivers' natural flow cycles, which are crucial to maintaining the health of the rivers, the species that live in or near them, and the seacoasts into which they flow.