Alluvial Soils and Floodplains

Alluvial soils are soils deposited by running water and are often located in existing floodplains. The DNR has developed a DNR AFO Siting Atlas that producers can check to determine if a potential animal feeding operation site would be located on alluvial soils, and, thus, possibly in a floodplain. Instructions for using the alluvial soils maps are available on the DNR AFO Maps site. See floodplain requirements below for confinements and for open feedlots.

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Floodplain Requirements for Confinement Feeding Operations

State law requires anyone wishing to build, modify or expand a confinement or manure storage structure located on alluvial soils to determine if the proposed site will be located in a 100-year floodplain. State law prohibits construction of a confinement in the 100-year floodplain of a major watersource. Use the DNR AFO Siting Atlas to check if your proposed site is on alluvial soils. You will need to know the township, range and section of the proposed location. Please document your findings from the map and submit that document with your construction design plans. Small animal feeding operations - please keep a copy of the documentation on-site, unless a construction permit is needed.

Confinements with less than 1,000 animal unit capacity using formed structures:
If the proposed location of a confinement with less than 1000 animal units is located on alluvial soils, the producer must petition the DNR for a declaratory order to determine if the site is in a 100-year floodplain. The petition must follow the format outlined in the 561 Iowa Administrative Code (IAC), 6.7. The DNR has developed a form for producers' convenience, " Petition for a Declaratory Order Form 542-8157," which animal producers may use.

Confinements needing a construction permit:
Confinements with 1,000 animal units or more using formed storage and all confinements using earthen storage are required to get an animal feeding operation construction permit before building, modifying or expanding. In this case, a petition is not required, because the DNR permitting engineer will take care of the request for a floodplain determination.

Floodplain Requirements for Open Feedlots

While open feedlots are not prohibited from constructing in alluvial soils, they must meet certain DNR requirements. For proposed open feedlot structures, a floodplain construction permit must be obtained if the drainage area is greater than 10 square miles. Producers can use the alluvial soils maps to determine if a proposed site could be located in a floodplain.