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Determinations of Wetlands on Agricultural Lands

Chapter 5 of the Regional Supplement to the Corps of Engineers Wetland Delineation Manual: Midwest Region should be utilized when making wetland determinations on agricultural lands.  Section 3(b) of the Regional Supplement discusses the National Food Security Act Manual (NFSAM) methodology to assist with these determinations.  The process for the NFSAM methodology method is as follows:

Determinations must be completed using the NFSAM methodology. The NRCS no longer certifies agricultural wetlands on cropland planned for development. Please contact the appropriate NRCS office to become familiar with the NFSAM methodology for identifying agricultural wetlands on your parcel. Once you have completed your determination submit your findings to this office so we may determine your information for acceptability. This information requirement will be added to our application checklist.

We are including the WETS tables for the major NWS precipitation recording stations in the Chicagoland area.  Use the data from the station closest to the site in question.  We have designated the wet years, normal years and alternate years of aerial slides to be reviewed.  Make sure you read the legend on the WETS tables carefully in order to review the proper years of slides. 

  1. Select a wet year as your base aerial photograph.  Typically, consistently wet areas should show wetland signatures in this year.  Reviewing this aerial photograph will make it easy to identify all the potential farmed wetlands.  If the wet year you have selected is not available, we have provided an alternate wet year that you can review.  If neither of these years are available, choose the most recent wet year available as your base map.
  2. Review the normal years we have selected for wetland signatures and to see how many years the areas identified in step 1 persist.  If the selected normal years are unavailable, we have provided alternate years to review.  If you are still having difficulty with slides that are unavailable or shadows on slides, select the most recent normal year(s) that are available.
  3. In the Chicago Region, use the hydrology criteria from the NRCS Wetland Mapping Conventions for the "Prairie Pothole and saturated soils in the Wisconsinan Glaciated Region", except for areas that flood.  For areas that flood (alluvial soils), use the criteria for Flooded or Ponded Soils.

The following information shall be submitted to this office as part of the wetland determination on agricultural lands:

  1. Submit a copy of the NRCS Farmed Wetland Inventory for the subject property.  Please note that this will be used by our office to identify potential farmed wetland areas on the subject property.  Areas designated as PC (Prior Converted Wetlands) are no longer relevant to the Corps.  PC areas may contain wetlands that redeveloped after NRCS completed their inventory, due to the failure of the drainage tile or the lack of maintenance to the drainage system.  The Chicago District is trying to identify the farmed wetlands that currently exist on the subject property.
  2. Submit a legible copy of the aerial photograph for every aerial slide year reviewed with the size and the shape of the wetland signatures identified and numbered. For example, if you review 6 years, you should submit 6 aerial photographs of the subject property. Each photograph shall have the interpretation of the wetland signatures corresponding to that specific year reviewed. The year should be written on the aerial photograph;
  3. Provide a final farmed wetland determination exhibit which shows all of the areas that showed wetland signatures in 50% or more of the photos reviewed.  For example, if an area shows up in 3 out of the 5 normal years then this area should be designated as a farmed wetland.  Take an average boundary of all of the years wetland signatures were apparent in that area.  You should identify the area (for example, Farmed Wetland 1) on the aerial photograph so that we can identify it in our jurisdictional determination letter;
  4. A copy of the worksheet used to plot the presence of wetland signatures for each aerial photograph reviewed; 
  5. A site visit should be made to verify that the areas that appeared as wetland signatures on the aerial photographs are in fact wetlands in the field.  A detailed data point should be taken in each farmed wetland within the project site limits. Field visits may also identify small wetlands that were not visible during the slide review.

Digital copies of slides are available for purchase from the following Soil and Water Conservation District (SWCD) offices:


Lake County and McHenry County, Contact McHenry County SWCD

Kane County and DuPage County, Contact Kane-DuPage County SWCD

Will County and South Cook County, Contact Will/South Cook SWCD.

North Cook County (Digitized copies are not currently available)