Winter 2000
Controlling open feedlot runoff
by Jeff Lorimor, Department of Agricultural and Biosystems Engineering
Controlling
open feedlot runoff needs to be addressed by feedlot operators across
the state. Feedlot runoff can kill fish and contribute nutrients to surface
waters that degrade water quality. The water quality of freshwater streams
and lakes has been of concern for many years; the Gulf of Mexico water
quality is a more recent concern.
The law. The Clean Water Act is a 1977 amendment to the Federal Water Pollution Control Act of 1972, which set the basic structure for regulating discharges of pollutants to waters of the United States. The Clean Water Act makes it unlawful for any person to discharge any pollutant from a point source into navigable waters unless a permit (National Pollutant Discharge Elimination System, NPDES) is obtained. Agricultural operations are not eligible for NPDES permits, which means they must capture runoff and pump it back onto agricultural land so it doesn’t run off.
The Clean Water Act requires controls to be installed below open feedlots. All lots, regardless of size, are required to install settling basins to remove solids from the runoff before they leave the lots. Large lots of more than 1,000 animal units (1 AU = a 1,000-lb beef animal) need settling basins to remove solids plus detention basins to catch and hold all liquid runoff. The captured runoff in the detention basin must then to be pumped or hauled for application to agricultural land. These large lots should have an operation permit, issued by the Iowa Department of Natural Resources (IDNR). The permit allows the lot to discharge whenever a large enough rain occurs, but not at any other time. Although the laws have been in place for nearly 30 years, they haven’t been rigorously enforced. The Environmental Protection Agency (EPA) is currently stepping up enforcement of these old laws as well as considering some revisions to the laws.
Why does the law require capture of runoff? Runoff must be captured because the water quality coming off feedlots is significantly less than we want in our lakes and streams: we don’t want them to be waste lagoons. The following are typical nutrient concentrations found in open-lot runoff after the solids are settled out: total nitrogen, 400 ppm; ammonia, 300 ppm; phosphorus, 80 ppm; and chemical oxygen demand (COD), 6,000 ppm. COD is the amount of oxygen required by microbes in the water.
Total ammonia is of concern because of hypoxia issues in the Gulf of Mexico. Ammonia more than 3–20 ppm kills fish. High COD deprives the water of oxygen, suffocating the fish. Phosphorus is of concern because of its effect on algal growth, even at very low levels (less than 1 ppm).
The size of settling basins and detention basins is defined by IDNR requirements. Typically, settling basins should be between 1/10 and 1/40 of the lot size. Detention basins should hold from 5 to 17 inches of runoff, depending on the frequency of pumpout. In both cases it’s obvious that the smaller the lot, the smaller the control facilities. Iowa State University Extension, Natural Resources Conservation Service, and private consulting engineers can help with specific basin designs.
As a feedlot operator, what should you do? If you are a lot owner or operator, you should have settling basins installed below your lot, and should be removing solids from the basin periodically so they work properly. If your lot holds more than 1,000 AU you also should have, or apply for, an operations permit. Doing so may require you to construct the above-mentioned control facilities, but may save you from being fined if EPA stops by your lot. Keep good records of liquid depth in your basin, pumpout times, and weather conditions.
It’s important to protect the state’s surface waters. The law requiring controls has been in place for nearly 30 years, but it’s now starting to be enforced more vigorously. To protect water quality and avoid legal and regulatory problems, you should move ahead with runoff control facilities on your open lots.
