Construction of the Tellico Dam became controversial for environmental reasons, as laws had changed since early development in the valley. Scientists and other researchers had become more aware of the massive environmental effects of the dams and new lakes, and worried about preserving habitats and species. The Tellico Dam project was initially delayed because of concern over the snail darter, a threatened species. A lawsuit was filed under the Endangered Species Act and the U.S. Supreme Court ruled in favor of protecting the snail darter in "Tennessee Valley Authority v. Hill" in 1978.