Proper Siting of an Animal Feeding Operation
using karst terrain and alluvial soils maps
The DNR has developed the AFO Siting Atlas to help livestock and poultry producers who are planning a new animal feeding operation, or the expansion or modification of an existing operation. These maps give a quick overview of the landscape features that must be considered when planning construction. The maps can be especially helpful in determining where alluvial soils, and thus potential floodplain areas; and karst topography and sinkholes.
Iowa laws have specific requirements for building, expanding or modifying open feedlots and confinement feeding operations located in the 100-year floodplain. Knowing if a potential site has alluvial soils is one step in determining if the site could be in a floodplain and if building restrictions could apply. Depending upon specific site conditions, construction may be prohibited or a floodplain permit may be required.
AFO Siting Atlas
All animal feeding operation structures have a "high damage potential," meaning flood protection (both structural integrity and elevation of the lowest opening) must be provided to the level of the 100-year floodplain plus one foot. In addition, the construction must allow for the conveyance of flood flows.
Iowa law also prohibits placing confinement feeding operations within 1,000 feet of a sinkhole, and sets specific separation distances from other protected waters. Animal producers who plan to build, modify or expand a confinement feeding operation structure will need to find out if the proposed location is in karst terrain.
Use the AFO Siting Atlas to evaluate potential sites for environmental concerns.
The animal feeding operations (AFO) Siting Atlas was created because of requests from the livestock industry. It’s designed to help producers evaluate potential locations for livestock and poultry sites. Producers, consultants and DNR staff can quickly locate a potential site and determine if a new or expanding facility is likely to be located on alluvial soils; or if a confinement site is proposed in karst terrain.
describe areas in Iowa that may be highly vulnerable to flooding or groundwater contamination. Alluvial soils were formed in materials that were deposited by running water, thus it is possible that a site located in alluvial soils is located in a floodplain. Karst terrain refers to those areas that have soluble bedrock close to the ground surface. Karst areas are often characterized by sinkholes and losing streams. Water and contaminants in these areas can travel quickly through underground passageways to wells, springs, and streams.
Refer to the Mapping (Interactive) pages
for general information about using interactive maps or use the specific instructions below for the AFO Siting Atlas. Check proper AFO siting
for more information on regulations.
Instructions for using the AFO Siting Atlas to check for potential alluvial soils or karst
Navigating the interactive map: Go to the Animal Feeding Operations (AFO) Siting Atlas
then click to enter.
Click on the red push pin icon below "Go to Legal." A small window will pop up. (If this step does not work, it is probably because you have a pop-up blocker turned on. You may need to adjust your internet security settings to use this feature.)
Type in the Tier, Range, and Section following the illustrated method. Click on Find Legal Description. This will take you directly to the section you have indicated, or to a menu. If you get the menu, click on the number of the section you wish to view.
Check the legend on the left side and be sure the "alluvial" and "karst" boxes have been checked. For better viewing, uncheck the "percent slope" box and check the "aerial photography (2008)." After checking and unchecking boxes, click on the "redraw map" icon at the bottom of the left side. Use the top toolbar icons to zoom in, pan out or move around the screen. For example, to zoom in, click the icon below "zoom in," then place your cursor over the area on the map that you want to enlarge.
Locate your site and determine whether the site is in "potential alluvial soils" (blue) or "within 1,000 feet of a mapped sinkhole" (pale red) or in "potential karst" (purple).
You will need to print out the map for documentation (see below). To print an image of your site, click on the print icon (on the left side of the screen). A pop-up box will come up with printing directions.
Map interpretation and documentation
Since it was impossible to analyze the soil and subsurface properties of every piece of land in Iowa, the Iowa Geologic Survey created maps that contain all of the potential karst and potential alluvial areas in the state. Producer who wish to locate a site in these potential areas will have to consult with an engineer, soil scientist or qualified staff from the USDA Natural Resources Conservation Service to confirm the mapping or submit documentation to refute the alluvial or karst mapping. Additional information about this process can be found in a fact sheet
under AFO Resources.
If the footprint of the proposed confinement or manure storage structure is within "Potential Alluvial Soils" (area shaded blue), please contact the DNR Flood Plain section at 866-849-0321.
If the footprint of the proposed confinement or manure storage structure is within "Karst" or "Potential Karst" (areas shaded red and purple), please contact the DNR animal feeding operations permitting engineer at 712-262-4177.
To document the determination, please attach a printed copy of the map, with the footprint of the proposed structure marked clearly, to the appropriate materials:
- Permitted confinements - Submit with construction permit application and send to DNR field office in Spencer.
- Non-permitted confinement sites - Submit with MMP and send to the appropriate DNR field office.
- SAFOs (small animal feeding operations) do not need to submit documentation, but should keep a copy with their plans.
If you receive correspondence from the DNR Flood Plain Section, please include a copy of that correspondence with your submitted materials.