A half century after the passage of the federal Clean Water Act, 50 percent of U.S. river and stream miles are so polluted that they are classified as “impaired,” a new report has found. … [N]one of these resources are suitable for public uses, according to the report. … California topped the charts for most river and stream miles listed as impaired for drinking water, while Louisiana ranked first for the most estuaries considered impaired for any use, according to the report.