Ground Water & Animal Waste Management Systems

The livestock industry in South Dakota is a very valuable segment of the state’s economy.

 

The proper storage and land application of the waste produced at livestock feeding operations can be used as a viable fertilizer resource rather than a waste product for disposal. An added benefit of properly collecting and using this waste is reducing the chance of surface and ground water contamination.

 

Information collected in South Dakota indicates that leaching of nutrients (primarily nitrogen) and other constituents from the feedlot manure to ground water can occur, and may do so at levels that would be detrimental to the environment and human health.

Picture of a Feed Lot
   

An oxygen depriving illness (methemoglobinemia) caused by drinking water with high levels of nitrate-nitrite may lead to serious and even fatal health effects in the elderly and the very young. Based on U.S. Environmental Protection Agency (EPA) health studies and requirements, the SD DENR proposed and the Water Management Board adopted 10 milligrams per liter (mg/L) as the regulatory standard for nitrate as Nitrogen in South Dakota ground water.

 

To prevent surface water contamination from feedlot runoff, a number of livestock producers have voluntarily or under regulatory requirements constructed animal waste management systems. These systems usually include at least one or more holding or storage ponds on the site. The ponds have been shown to be very effective in reducing contamination of streams and lakes.


If the ponds are located over permeable soils, such as sandy or gravelly soils, and are not lined with clay or there is failure of the liner, there is an increased risk of ground water contamination. This risk of ground water contamination occurs because all of the runoff from the lots is concentrated in a relatively small pond for a long period of time.

 

Because of the weight of the liquid waste above the pond bottom, the risk of wastes leaking or leaching to the ground water greatly increases. Concerns arise because: 1) excessive leaching causes a loss of a valuable economic resource in the fertilizer value of the liquid waste, and 2) leaching may cause contamination of ground water, the owner/operator’s water well or wells, or may impact the neighbors’ wells. Once the ground water is contaminated, its is very costly to clean it up and return it to its natural quality.

 
Review of AWMS for Impacts to Ground Water
 

Because of these concerns the Ground-Water Quality Program of the DENR reviews the Plans & Specifications for animal waste management systems. The DENR conducts a review of area soil borings, well logs, and available local studies to determine the presence of any aquifers that could be impacted under the site. If there is sufficient data to confirm the presence of a shallow aquifer, ground water monitoring wells are required.


Monitoring is required where ground water is of good quality and is present in sufficient quantity to be used. Monitoring is not required in areas where there is a thick layer of impermeable material (such as unweathered clay) between the land surface and the aquifer, since this would prevent the contaminants from reaching the ground water table. Site geology can vary widely, so each site must be reviewed on a case-by-case basis.


Where possible, it is desirable to place the animal waste management system away form lowland or creek bottom areas which often are associated with shallow, vulnerable aquifers. Also, to avoid possible pollution of on-site wells, the operator should try to place his animal waste management system downgradient or away from any wells, and the wells should be inspected periodically to be sure they are properly sealed.


Based on these above criteria, the majority of the animal waste management systems in South Dakota are located in areas that are not vulnerable to contamination and therefore do not need monitoring wells. If monitoring is required and significant levels of contamination are found in the monitoring wells, the DENR will work with the operator to help correct the problem and protect his shallow ground water supply.


Livestock producers in South Dakota have been good stewards of the natural resources in the state. As production increases more attention must be given to using feedlot runoff and animal wastes as a fertilizer resource. However, in storing and using these wastes for later land application, producers need to be aware of the potential for ground water pollution, so that the solution of one environmental issue does not create another.


For more information contact Tom Brandner at 773-3296 or Click Here for more information on Animal Waste Management Systems in DENR.