Parts of northwest Iowa saw up to 10 inches of rain over the last couple of days, which caused manure systems at nearly 30 livestock operations to overflow.
Iowa’s Department of Natural Resources said most of the overflow manure from 28 livestock operations, primarily in Clay, Lyon, O’Brien and Sioux counties, is polluting creeks and rivers. Officials have been working with facilities to keep pollutants from going into state waterways.
State Sen. David Johnson, I-Ocheydan, said he noticed rivers close to or over their banks while driving through northwest Iowa on Thursday, and he is concerned.
“It’s a potential health risk any time you have excessive amounts of manure and you happen to be in a situation where there’s a lot of flooding,” he said.
In huge rain events, there is not a lot the state can do besides provide guidance to producers, said Lois Benson, an environmental specialist with Iowa's Department of Natural Resources.
She says producers have fallen behind on their routines because of heavy rain and flooding.
“Typically they would have all their silage out now and they would already be applying this manure according to the agronomic guidelines that they have,” Benson said. “But several that I talked to yesterday [Thursday] – they’re not even done with their silage and that’s two to three weeks behind at least.”
After silage – or chopped corn – is removed from the ground, producers can apply manure there.
Sen. Johnson said this is a reminder that the state has a long way to go in imposing manure management requirements.
Livestock operations are required to have federal permits that regulate their discharge. Benson said as long as a producer is complying with their permit, “they're doing what we [the DNR] ask of them.”
According to the state’s 2011 Design Criteria for Livestock Waste Control Systems At Open Feedlot Medium CAFOs, “All runoff of manure, liter or process wastewater resulting from a precipitation event less than or equal to a 5-inch, 24-hour, rainfall event shall be collected, stored and land applied.”
But some parts of Iowa recently exceeded a 24-hour 5-inch rain event. The National Weather Service of Sioux Falls on Friday reported more than 10 inches of rain in Spencer (in Clay County) over a 72-hour period. According to Meteorologist Jim Murray, the city received 5.45 inches over a 24-hour period from Wednesday to Thursday.
Iowa State University Extension Field Agronomist Joel DeJong, who is based in northwest Iowa, said manure facilities with outdoor storage are typically designed to allow enough wiggle room in the case of a large rain event.
“But this has been an incredibly wet situation this year,” DeJong said.
And the rain further limits farmers in when they can land-apply manure, he said.
“You can’t apply it when it is muddy. You can’t apply it when there’s a fully grown crop out there,” DeJong said. “That limits the time of year when you can get there, and if you get weather in the way of the timeliness it puts even more pressure on the design of the facility.”
According to the DNR, more than a dozen northwest Iowa communities also reported wastewater treatment discharge plants.
The DNR recommends staying out of floodwaters until they retreat.