DES MOINES, Iowa (AP) — Environmental activists are asking the U.S. Environmental Protection Agency to withdraw the Iowa Department of Natural Resources’ authority to manage a program designed to limit water pollution.

About 30 members of the group Iowa Citizens for Community Improvement held a state Capitol rally Tuesday. They distributed a letter to the EPA alleging the DNR hasn’t done enough to regulate large hog farms, which can pollute water. The group is asking federal officials to manage water pollution regulations.

The DNR accepted a five-year work plan with the EPA in 2013 to bring its oversight of a pollutant discharge program into compliance with federal regulations. A department spokesman says the DNR is “sufficiently following” the plan.

The EPA will decide on any further action following a final DNR report in August.