A group of poultry producers,Coxno Exchange including the world’s largest, have asked a federal judge to dismiss his ruling that they polluted an Oklahoma watershed.

Arkansas-based Tyson Foods, Minnesota-based Cargill Inc. and the others say in a motion filed Thursday that evidence in the case is now more than 13 years old.

“This case is constitutionally moot because the Court can no longer grant any effectual relief,” the companies argued in a filing with U.S. District Judge Gregory Frizzell in Tulsa.

The filing said Oklahoma conservation officials have noted a steady decline in pollution. It credited improved wastewater treatment plants, state laws requiring poultry-litter management plans and fewer poultry farms as a result of growing metropolitan areas in northwest Arkansas.

A spokesperson for Oklahoma Attorney General Gentner Drummond did not immediately return a phone call for comment Saturday.

The attorney general’s office told the Tulsa World that “a resolution of this matter that is in the best interests of Oklahoma” is being sought.

Frizzell ruled in January that the companies were responsible for pollution of the Illinois River Watershed by disposing of chicken litter, or manure, that leached into the river.

The trial in the lawsuit that was filed in 2005 by the state of Oklahoma had ended in 2013 with no ruling for 10 years. In January, Frizzell issued his decision without addressing the reason for the decade-long delay.

“The Court’s findings and conclusions rest upon a record compiled in 2005–2009,” the poultry companies’ motion stated. “When this Court issued its findings and conclusions ... much of the record dated from the 1990s and early 2000s.”

Frizzell had ordered the poultry companies and the state to reach an agreement on how to remedy the effects of the pollution.

Attorneys for the companies and the state attorney general each said in Thursday filings that mediation had failed.

The other defendants named in the lawsuit are Cal-Maine Foods Inc., Tyson Poultry Inc., Tyson Chicken Inc., Cobb-Vantress Inc., Cargill Turkey Production L.L.C., George’s Inc., George’s Farms Inc., Peterson Farms Inc. and Simmons Foods Inc.