Which legislation was enacted to restore and maintain the chemical, physical and biological integrity of the nation's waters?

The Clean Water Act is the correct choice because it was specifically enacted to restore and maintain the chemical, physical, and biological integrity of the nation's waters. The Act set the framework for regulating discharges of pollutants into the waters of the United States and gave the U.S. Army Corps of Engineers and the Environmental Protection Agency authority to implement water quality standards. It emphasizes the importance of maintaining healthy aquatic ecosystems and ensuring clean water for both human use and the environment, making it a cornerstone of federal water pollution control policy.

While other options may relate to environmental issues, they do not specifically target the preservation and health of water resources in the way the Clean Water Act does. The Environmental Protection Act, for instance, encompasses a broader range of environmental protections beyond water.