HEALTH RISKS of USING GRAY SOIL COLORS to DETERMINE ONSITE SUITABILITY Jay F. Conta - Virginia Tech Interpretive Soil Scientist Department of Crop & Soil Environmental Sciences
WATER TABLE RESEARCH SITE
MATERIALS AND METHODS
SOILS STUDIED Emporia sandy loam: Fine-loamy, siliceous, subactive, Thermic, Typic Hapludult Two research sites in Henrico County, Virginia Both sites in residential subdivisions
Henrico County Precipitation Comparison Nov - Dec 99: 42% of long-term average Jan - May 00: near normal (29 yr average) Oct - Dec 00: 41% of long-term average Jan - May 01: 75% of long-term average
Hydrograph at Ryall Road Site November 1999- June 2000 NOV/ DEC / JAN / FEB / MAR / APR / MAY / JUN Depth Below Surface (inches) 0 -10 -20 Strong Brown Concentrations -30 Str Brown & Very Pl Brown -40 Features -50 Gray Depletions Well #1
Ryall Road: Nov 18, 1999 - May 11, 2000 During this 176 day period where there was water in the observation well: Depth ( in.) Redox Feature # Days % Cumulative Days 0 - 16 None 5 3 16.1- 29 St Brown 112 64 29.1- 41 St Brown & 176 100 Very Pl Brown
Hydrograph at Ryall Road Site December 2000- May 2001 DEC / JAN / FEB / MAR / APR / MAY 0 -5 -10 Depth Below Surface (inches) -15 -20 Strong Brown Concentrations -25 -30 Strong Brown & Very Pl Brown -35 Features -40 Gray -45 Depletions Well #1
Ryall Road: Dec 17, 2000- May 2, 2001 During this 137 day period where there was water in the observation well: Depth ( in.) Redox Feature # Days % Cumulative Days 0 - 16 None 8 6 16.1- 29 St Brown 68 50 29.1- 40.3 St Brown & 122 89 Very Pl Brown 40.4 - Dry Hole 11 100
Summary of Ryall Road Site This residence utilized a Puraflo onsite system, with the gravel pad at a depth of 18- 24 inches. This system was designed and installed in compliance with the Sewage Regulations and the manufacturer’s recommendations . Based on this research, the seasonal water table was into the peat moss containers, the gravel pad or the 12 inch standoff zone ( beneath the pad ) at least 1/2 to 2/3 of the time during a winter- spring period.
Summary of Ryall Road Site The Puraflo system directly discharged into the shallow seasonal water table for extended periods of time. The Emporia soil clearly met the Oxyaquic criteria. Even during a drought, horizons with strong brown redoximorphic features were saturated for 1/2 to 2/3 of the time during the winter- spring periods.
Summary of Ryall Road Site Even during a drought, horizons with strong brown & very pale brown redoximorphic features were saturated for 90- 100 % of the time during the winter- spring periods. The presence of redox features clearly relates to the duration of soil wetness. The seasonal water table will be significantly closer to the ground surface than the depth to gray depletions, for extended periods of time.
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