Geology topics

Research about Sheffield, Illinois

Source-linked reports with geographic coverage including Sheffield, Illinois.

3 recordsLinked to original sources

USGS1991

Variability of an unsaturated sand unit underlying a radioactive- waste trench

Properties of soils vary considerably within any field. This study was conducted to investigate the variability in properties of an unsaturated sand unit that lies at a depth of 13 m below land surface. Four-hundred-forty soil core samples, obtained from a 1.75 by 18-m horizontal plane within a sand unit underlying a waste trench, were used to describe the variability of moisture content, tritium concentration, and several physical properties. A simple model based on unit-gradient theory was used to calculate fluxes of water and tritium through the study plane. The effects of including spatial variability of properties in model calculations were examined. The sand was uniform in terms of median particle size, bulk density, and proposity, but several variables, including saturated hydraulic conductivity ( K s ) and tritium concentration, showed considerable variability. In general, correlation coefficients calculated between variables were low. Spatial correlation structures were identified for moisture content, tritium concentration, and a few particle-size variables, but were absent for K s and most other variables. Variances of K s and field-measured volumetric moisture content (θ) were lower than published values for soils. Model-calculated fluxes of water and tritium that accounted for spatial variability of properties were considerably higher than those that did not account for the variability. Model results were more sensitive to changes in θ and residual moisture content (each parameters of the relative hydraulic conductivity function) than to changes in K s .

Illinois↗

USGS1989

Diffusion and consumption of methane in an unsaturated zone in north-central Illinois, U.S.A.

The distribution of CH 4 in unsaturated glacial and eolian deposits adjacent to buried low-level radioactive waste was measured, and movement of the gas from the waste source was simulated using a two-dimensional finite-difference model for gas diffusion in the unsaturated zone. Mean P CH 4 was greatest (1.56 Pa) in a pebbly-sand deposit 11.6 m below the land surface and 12 m from the waste, and generally decreased with increased horizontal distance from the waste. Mean P CH 4 was least (0.07 Pa) at depth of 1.8 m below land surface, regardless of distance from the waste. P CH 4 at the land surface averaged 0.17 Pa. Depth versus P CH 4 profiles suggest consumption of both waste-produced and atmospheric CH 4 in the upper unsaturated zone, presumably by methanotrophic microorganisms. Numerical simulations of methane movement support the consumption observation; inclusion of a term in the model for consumption of CH 4 in the upper 2 m of the unsaturated zone resulted in simulated P CH 4 within 30% of mean P CH 4 at eleven of thirteen sampling locations. A similar fit of the data was obtained for only four locations when consumption was not considered.

Illinois↗

USGS1989

Seepage through a hazardous-waste trench cover

Water movement through a waste-trench cover under natural conditions at a low-level radioactive waste disposal site in northwestern Illinois was studied from July 1982 to June 1984, using tensiometers, a moisture probe, and meteorological instruments. Four methods were used to estimate seepage: the Darcy, zero-flux plane, surface-based water-budget, and groundwater-based water-budget methods. Annual seepage estimates ranged from 48 to 216 mm (5-23% of total precipitation), with most seepage occurring in spring. The Darcy method, although limited in accuracy by uncertainty in hydraulic conductivity, was capable of discretizing seepage in space and time and indicated that seepage varied by almost an order of magnitude across the width of the trench. Lowest seepage rates occurred near the center of the cover, where seepage was gradual. Highest rates occurred along the edge of the cover, where seepage was highly episodic, with 84% of the total there being traced to wetting fronts from 28 individual storms. Limitations of the zero-flux-plane method were severe enough for the method to be judged inappropriate for use in this study.Water movement through a waste-trench cover under natural conditions at a low-level radioactive waste disposal site in northwestern Illinois was studied from July 1982 to June 1984, using tensiometers, a moisture probe, and meteorological instruments. Four methods were used to estimate seepage: the Darcy, zero-flux plane, surface-based water-budget, and groundwater-based water-budget methods. Annual seepage estimates ranged from 48 to 216mm (5-23% of total precipitation), with most seepage occurring in spring. The Darcy method, although limited in accuracy by uncertainty in hydraulic conductivity, was capable of discretizing seepage in space and time and indicated that seepage varied by almost an order of magnitude across the width of the trench. Lowest seepage rates occurred near the center of the cover, where seepage was gradual. Highest rates occurred along the edge of the cover, where seepage was highly episodic, with 84% of the total there being traced to wetting fronts from 28 individual storms. Limitations of the zero-flux-plane method were severe enough for the method to be judged inappropriate for use in this study.

Illinois↗