LOUISVILLE — The Kentucky Waterways Alliance joined conservation groups from eight other states along the Mississippi River in asking the federal government to take steps to clean up the river and the Gulf of Mexico.

The groups petitioned the Environmental Protection Agency on Wednesday to set standards to limit nitrogen and phosphorus pollution. Jason Flickner of the alliance said Kentucky contributes 9 percent of the phosphorous and 6 percent of the nitrogen that are causing a large dead zone in the gulf.

The petition came after a Monday report that the dead zone covers 8,000 square miles — the second-largest area since it has been monitored — and would have been larger if Hurricane Dolly hadn't churned up the water, adding oxygen.