Identifying Problematic Hydric Soils Derived from Red Parent Materials in the United States.

Section 404 of the Clean Water Act requires the delineation of hydric soils as a parameter for wetland preservation in the United States. Some soils, derived from certain Red Parent Materials (RPM), have a relatively unexplored resistance to developing typical hydric soil morphology, and are therefore problematic to correctly identify in the field without the assistance of guidance maps. The objectives of this project are to: 1) determine which groups of soils and associated geological formations qualify as problematic RPM; 2) better understand problematic RPM soil resistance to develop typical hydric soil morphology; and 3) create geospatial datasets and guidance maps for the distribution and occurrence of problematic RPM soils in major regions across the United States. Soil samples will be solicited from Soil and Wetland scientists from the Natural Resource Conservation Service and U.S. Army Corps of Engineers regional offices. Soils will be assessed as problematic using a Color Change Propensity Index (CCPI) by treating samples with a citrate-buffer and sodium dithionite solution for varying periods of time and measuring soil colors with a digital colorimeter. RPM resistant behavior will be explored by fractionating samples into particle sizes and observing samples after CCPI analyses with a petrographic microscope. Mineralogical analyses of samples may also be pursued on fractionated samples using X-ray Diffraction (XRD). Identified problematic RPM soils will then be correlated to soil series, map units, and geological formations from the Soil Survey Geographic (SSURGO) database and other geological datasets using ArcGIS. This project looks to eliminate erroneous hydric soil (and wetland) delineations by improving awareness and locality of RPM soils using guidance maps of RPM occurrence throughout the country. Current project completion and general participation in the project will be discussed.