DES MOINES, Iowa — At least 20 Iowa farms have reported incidents of hog and cattle manure runoff from flooding due to the heavy rains in June, with overflow affecting the control of nitrate levels in residential drinking water, according to the Iowa Department of Natural Resources (IDNR).
"Small- and medium-size open feedlots can potentially discharge significant amounts of nutrients to streams," said Shawn Shouse, Iowa State University extension agricultural engineer. "The nutrients can cause water quality problems in streams and present a loss of valuable fertilizer nutrients for the farm."
The IDNR said the state’s June rains ranked as the fourth wettest month in 141 years, with rainfall bringing precipitation to above-normal levels during the first half of 2014.
The June statewide average rainfall was almost 10 inches, and for the most recent two weeks, the rainfall of 4.3 inches was nearly double the normal of 2.2 inches, the department added, with all occurring in the northwest part of the state, from Lyon to Ida counties. Sioux City in southwest Iowa reported its highest monthly rainfall ever recorded in June 2014 (more than 16 inches).
The IDNR said some of the animal feeding operations have National Pollutant Discharge Elimination System (NPDES) permits, which allow them to discharge when rainfall exceeds a 25-year, 24-hour rain event.
"Generally, that’s about five inches of rain within 24 hours," said Tim Hall, the IDNR’s Iowa Geological and Water Survey bureau chief. "Some operations discharge to protect their manure storage facilities, while others may overflow due to excess storm water runoff.
"Some livestock producers are pumping to pastures or other basins," he added, "making it less likely the effluent will reach a water of the state."
Iowa Citizens for Community Improvement (ICCI), the state’s largest environmental activist group, has been complaining about the reported runoffs, asking the IDNR for tighter water protection regulations.
According to the Associated Press, the ICCI claimed "farms should be required by clean water permits to increase manure storage capacity or reduce herd size so they are handling less manure."
"IDNR records show at least 20 incidents in the last half of June of overflowing manure storage basins or feedlots washed out, causing manure to flow into fields, ditches and in a few cases streams," the AP reported on July 14. "Manure flowing into streams makes it difficult for drinking water providers like Des Moines Waterworks to remove high levels of nitrate."
However, Kevin Baskins, IDNR communications bureau chief, said this was not a typical rain event as evidenced by the Rock River in northwest Iowa exceeding its previous high crest by four feet.
He said 18 of the 20 reported facilities had NPDES permits (reporting is required by permit): "One confinement called in to report their reception pit had been flooded," he said. "(But) no discharge was reported."
He added that three facilities reported full basins but no overflow or discharge to a creek, with one open cattle lot with no NPDES permit calling to report manure transfer but not discharge.
He said 80 percent of the (FO3) NPDES permitted facilities were able to retain all the runoff, even with the record rainfall: "No discharges were reported from any confinement facility in northwest Iowa," out of thousands of facilities in that part of the state.