Nebraska Soils Field Trip - Virginia Tech

4th IUSS Soil Classification Conference Field Tour Guidebook
Soils at pit one experienced settling several years ago and ponded water. The original design of
the landfill cap was to shed water and minimize infiltration. Additional fill was brought in 3
years ago to eliminate the ponding and help stop further settling. As a result, pit 1 contains a
buried soil under a 47 cm mantle of new soil material. The proposed ICOMANTH changes
eliminate the sliding scale (30-50 cm) used for HTM and this soil would no longer be classified
as a buried soil in Soil Taxonomy. The ICOMANTH proposal for HATM material classes would
place this soil in a spolic class even though subsidence is known to have occurred at the site.
The soil at pit 2 contains many artifacts and what we believe to be reduction of iron without
saturation by ground water. No evidence for a perched water table (i.e., episaturation) or a
seasonal high water table (i.e., endosaturation) exists for the site. Methane production is
assumed given the artifacts present in the soil and the unpleasant smells (e.g., methanethiol or
methyl mercaptan) associated with rotting garbage. Methane production from a landfill such
as this would drive out the oxygen from the soil and provide a carbon source for reduction
reactions to occur. The ICOMANTH proposal for HATM material classes would place this soil in a
methanogenic class. The methanogenic class is the first class in the key to human-altered and
human-transported material classes to highlight the significance of using soils which potentially
emit dangerous amounts of methane gas.
The soil at pit 2 contains a weakly developed cambic horizon, as does the buried soil at pit 1. Is
a few decades adequate elapsed time for pedogenic processes to form cambic horizons in the
absence of fluctuating ground water?
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