Hydropedology of Problematic Interfluve Soils in the Central Piedmont of Virginia.

Onsite wastewater disposal systems have failed prematurely in upland transported soils containing chroma ≥3 redoximorphic features (RMFs).  Soil hydrology of the Appomattox and Bentley Soil Series was documented with recording wells and piezometers over three years at eight experimental sites in the central Piedmont of Virginia.   Our objectives were (i) to relate saturation with active RMFs, (ii) confirm epiaquic conditions, (iii) explore saturation differences between entirely residual and transported soils, and (iv) determine  the effect of canopy cover on water table duration and height.   Transported soils containing RMFs on flat broad summits had an average water table depth of -87 cm along with -66 cm and -86 cm average depths to the 30-d and 20-d oxyaquic criteria, respectively.  Depleted ped faces (n=36), concentrations (n=11),  chroma 3 depletions (n=20), and  chroma 2 depletions (n=12) were saturated for 41, 23, 41, and 65%, respectively, when water tables were  highest.   Residuum found ≥ 1.5 m underneath transported material showed very little or no saturation.  Epiaquic conditions were confirmed at six out of the eight sites.   Entirely residual soils without overlying transported material on  linear summits with >50 cm thick impermeable layers did not perch water for extended periods (20-d oxyaquic criteria), but met the 30-d oxyaquic criteria (83 cm).  Transported soils with an open canopy had an average water table of 79 cm and met the 30-d and 20-d oxyaquic conditions at 58 cm and 86 cm respectively, while those with wooded canopies met the 20-d oxyaquic criteria at only one site, had a deeper average water table (-85 cm), and met the 30-d oxyaquic conditions deeper (-84 cm) than transported soils with an open canopy.  In summary, transported soils containing RMFs on flat broad summits perch water seasonally for extended periods on top of thick impermeable layers associated with a lithologic discontinuity.