Geology topics
Research about Illinois
Source-linked reports with geographic coverage including Illinois.
Floods of September 26-October 4, 1986, and August 14-17, 1987, in Illinois
No abstract available.
Bluff recession rates along the Lake Michigan shoreline in Illinois
For two time periods, 1872-1937 and 1937-1987, rates of retreat vary from 10 to 75 cm/yr between discrete segments of bluffs (defined by lithology) and between time periods for a given bluff segment. The average retreat rates for the entire area, however, do not vary significantly between the two time periods and are approximately 20-25 cm/yr. The temporally constant regional retreat rates and the regular shape of the local shoreline indicate that a long-term uniform rate of retreat prevails and that local variations in rates balance out through time to produce long-term parallel (in map view) bluff retreat in the area.
Floating sample-collection platform with stage-activated automatic water sampler for streams with large variation in stage
A floating sample-collection platform is described for stream sites where the vertical or horizontal distance between the stream-sampling point and a safe location for the sampler exceed the suction head of the sampler. The platform allows continuous water sampling over the entire storm-runoff hydrogrpah. The platform was developed for a site in southern Illinois.
Effects of low-level radioactive-waste disposal on water chemistry in the unsaturated zone at a site near Sheffield, Illinois, 1982-84
A 1982-84 field study defined the chemistry of water collected from the unsaturated zone at a low-level radioactive-waste disposal site near Sheffield, Bureau County, Ill. Chemical data were evaluated to determine the principal, naturally occurring geochemical reactions in the unsaturated zone and to evaluate waste-induced effects on pore-water chemistry. Samples of precipitation, unsaturated-zone pore water, and saturated-zone water were analyzed for specific conductance, pH, alkalinity, major cations and anions, dissolved organic carbon, gross alpha and beta radiation, and tritium. Little change in concentration of most major constituents in the unsaturated-zone water was observed with respect to depth or distance from disposal trenches. Tritium and dissolved organic carbon concentrations were, however, dependent on proximity to trenches. The primary reactions, both on-site and off-site, were carbonate and clay dissolution, cation exchange, and the oxidation of pyrite. The major difference between on-site and off-site inorganic water chemistry resulted from the removal of the Roxana Silt and the Radnor Till Member of the Glasford Formation from on-site. Off-site, the Roxana Silt contributed substantial quantities of sodium to solution from montmorillonite dissolution and associated cation-exchange reactions. The Radnor Till Member provided exchange surfaces for magnesium. Precipitation at the site had an ionic composition of calcium zinc sulfate and an average pH of 4.6. Within 0.3 meter of the land surface, infiltrating rainwater or snowmelt changed to an ionic composition of calcium sulfate off-site and calcium bicarbonate on-site and had an average pH of 7.9; below that depth, pH averaged 7.5 and the ionic composition generally was calcium magnesium bicarbonate. Alkalinity and specific conductance differed primarily according to composition of geologic materials. Tritium concentrations ranged from 0.2 (detection limit) to 1,380 nanocuries per liter. The methods of constructing, installing, and sampling with lysimeters were evaluated to ensure data reliability. These evaluations indicate that, with respect to most constituents, the samples retrieved from the lysimeters accurately represented pore-water chemistry.
Effects of wetlands creation on groundwater flow
Changes in groundwater flow were observed near four Experimental Wetland Areas (EWAs) constructed along a reach of the Des Plaines River in northeastern Illinois. These changes were observed during monthly monitoring of groundwater elevation in nested piezometers and shallow observation wells before and after the wetlands were filled with water. A numerical model was calibrated with observed data and used to estimate seepage from the wetlands into the Des Plaines River. After the wetlands became operational, groundwater levels in adjacent wells increased by about 0.5m, while water levels in wells distant from the wetlands decreased. The increase in groundwater levels near the wetlands is a result of seepage from the wetlands. Numerical predictions of seepage from the wetlands are 60–150 m 3 day −1 for two wetlands situated over sand and gravel and less than 1 m 3 day −1 for two wetlands situated over clayey till. The difference in seepage rates is attributed to two factors. First, the hydraulic conductivity of the sand and gravel unit is greater than that of the till, and thus there is less mounding and a greater capacity for transmitting water beneath the wetlands overlying this deposit. Secondly, the wetlands located over till are groundwater flow-through ponds, whereas the wetlands over the sand and gravel are primarily groundwater recharge areas. The model was used to estimate that seepage from the wetlands will double groundwater discharge into the Des Plaines River and a tributary relative to pre-operational discharge from the study area. Overall, the wetlands have acted as a constant head boundary, stabilizing groundwater flow patterns.
The southeastern Illinois earthquake of 10 June 1987: The later aftershocks
The 10 June 1987 southeastern Illinois earthquake (mbLg = 5.2) was the seventh in a series of moderate magnitude (≧ 4.5) MMI VII shocks to occur in the Wabash Valley seismic zone of southeastern Illinois and southwestern Indiana since 1891. Located about 200 km east of St. Louis, Missouri, the shock caused minor damage in the epicentral area, had a contiguous felt area of about 433,000 km2, and had a total felt area over 1 million km2. Within 47 hours after the main shock, a cooperative effort between the U.S. Geological Survey and Memphis State University installed a 15-station aftershock monitoring network (later expanded to 21 instruments) that recorded more than 100 aftershocks in the following 4-day period. Results from the 56 aftershocks that were well located indicate a compact, cylindrically shaped aftershock volume about 1.7 km long, 0.8 km wide, and with a vertical distribution between about 9 and 12 km in depth. Composite focal mechanism solutions of the aftershocks suggest that the predominant mode of faulting is reverse slip, but some strike-slip type motion occurred similar to the mechanism for the main shock as determined from teleseismic data. The maximum principal compressive stress (P axes) is oriented easterly to east-southeasterly and is subhorizontal in plunge. These results, combined with historical observations and the recent discovery of earthquake-induced liquefaction features in the area, imply that the seismic potential of the zone may be greater than generally perceived.
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 .
Water and tritium movement through the unsaturated zone at a low-level radioactive-waste disposal site near Sheffield, Illinois, 1981-85
The movement of water and tritium through the unsaturated zone was studied at a low-level radioactive-waste disposal site near Sheffield, Bureau County, Illinois, from 1981 to 1985. Water and tritium movement occurred in an annual, seasonally timed cycle; recharge to the saturated zone generally occurred in the spring and early summer. Mean annual precipitation (1982-85) was 871 millimeters; mean annual recharge to the disposal trenches (July 1982 through June 1984) was estimated to be 107 millimeters. Average annual tritium flux below the study trenches was estimated to be 3.4 millicuries per year. Site geology, climate, and waste-disposal practices influenced the spatial and temporal variability of water and tritium movement. Of the components of the water budget, evapotranspiration contributed most to the temporal variability of water and tritium movement. Disposal trenches are constructed in complexly layered glacial and postglacial deposits that average 17 meters in thickness and overlie a thick sequence of Pennsylvanian shale. The horizontal saturated hydraulic conductivity of the clayey-silt to sand-sized glacial and postglacial deposits ranges from 4.8x10^-1 to 3.4x10^4 millimeters per day. A 120-meter-long horizontal tunnel provided access for hydrologic measurements and collection of sediment and water samples from the unsaturated and saturated geologic deposits below four disposal trenches. Trench-cover and subtrench deposits were monitored with soil-moisture tensiometers, vacuum and gravity lysimeters, piezometers, and a nuclear soil-moisture gage. A cross-sectional, numerical ground-water-flow model was used to simulate water movement in the variably saturated geologic deposits in the tunnel area. Concurrent studies at the site provided water-budget data for estimating recharge to the disposal trenches. Vertical water movement directly above the trenches was impeded by a zone of compaction within the clayey-silt trench covers. Water entered the trenches primarily at the trench edges where the compacted zone was absent and the cover was relatively thin. Collapse holes in the trench covers that resulted from inadequate compaction of wastes within the trenches provided additional preferential pathways for surface-water drainage into the trenches; drainage into one collapse hole during a rainstorm was estimated to be 1,700 liters. Till deposits near trench bases induced lateral water and tritium movement. Limited temporal variation in water movement and small flow gradients (relative to the till deposits) were detected in the unsaturated subtrench sand deposit; maximum gradients during the spring recharge period averaged 1.62 millimeters per millimeter. Time-of-travel of water moving from the trench covers to below the trenches was estimated to be as rapid as 41 days (assuming individual water molecules move this distance in one recharge cycle). Tritium concentrations in water from the unsaturated zone ranged from 200 (background) to 10,000,000 pCi/L (picocuries per liter). Tritium concentrations generally were higher below trench bases (averaging 91,000 pCi/L) than below intertrench sediments (averaging 3,300 pCi/L), and in the subtrench Toulon Member of the Glasford Formation (sand) (averaging 110,000 pCi/L) than in the Hulick Till Member of the Glasford Formation (clayey silt) (averaging 59,000 pCi/L). Average subtrench tritium concentration increased from 28,000 to 100,000 pCi/L during the study period. Within the trench covers, there was a strong seasonal trend in tritium concentrations; the highest concentrations occurred in late summer when soil-moisture contents were at a minimum. Subtrench tritium movement occurred in association with the annual cycle of water movement, as well as independently of the cycle, in apparent response to continuous water movement through the subtrench sand deposits and to the deterioration of trench-waste containers. The increase in concentrations of tritium with increasing distance from the trench bases in the sand unit indicates that water movement through the unit may be more pronounced than indicated by the pressure-head data. Localized, preferential flow paths may have gone undetected by the monitoring instruments used in the study.
Changes in chloride concentration in water from municipal wells that tap aquifers in rocks of Cambrian and Ordovician age in northeastern Illinois, 1915–84
During the past few decades, several municipalities in northeastern Illinois have noted increases in the salinity of water from wells that tap aquifers in rocks of Cambrian and Ordovician age. The municipalities have discontinued the use of, or sealed-off sections of, those wells. The aquifers involved include the Ancell, the Ironton-Galesville, and the Elmhurst-Mt. Simon. To define the location, magnitude, and possible causes for the salinity increases in the six northeastern counties of Illinois, 17 municipal wells and 1 deep test well were selected on the basis of their proximity to major pumping centers, the availability of water-quality data, and their documented maintenance history. Well depths ranged from about 960 to 3,475 feet. One well was finished in the middle confining unit, 2 wells were finished in the Ironton-Galesville aquifer, 4 wells were finished in the Eau Claire confining unit, and 10 wells were finished in the Elmhurst-Mt. Simon aquifer. The deep test well was finished below the Elmhurst-Mt. Simon aquifer in Precambrian-age rock. Chloride concentrations in the municipal wells ranged from less than 5 to greater than 600 milligrams per liter; in the deep test well, they ranged from 13 t o 37,000 milligrams per liter. Some changes in the chloride concentration in water from the studied municipal wells can be related to physical changes to the wells, including the partial filling in of a well, bridging within a well, the cleaning out of a well, or the deepening of a well. Some changes in chloride concentration are not related to physical changes but may be caused by increased pumpage; changes in pumping rate, frequency, or duration; cessation of pumping; improper abandonment of wells; and the upconing of highly mineralized water. The data base was inadequate for a quantitative study of the changes in chloride concentration in water from individual aquifers in rocks of Cambrian and Ordovician age.
A Concept Plan for Enhancement of Fish and Wildlife Resources at Calhoun Point, Illinois
No abstract available.
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.
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.
Results of hydrologic research at a low-level radioactive-waste disposal site near Sheffield, Illinois
Ten years of hydrologic research have been conducted by the U.S. Geological Survey at a commercial low-level radioactive-waste disposal site near Sheffield, Illinois. Research included studies of microclimate, evapotranspiration, and tritium release by plants; runoff and land modification; water movement through a trench cover; water and tritium movement in the unsaturated zone; gases in the unsaturated zone; water and tritium movement in the saturated zone; and water chemistry. Implications specific to each research topic and those based on overlapping research topics are summarized as to their potential effect on the selection, characterization, design, operation, and decommissioning processes of future low-level radioactive-waste disposal sites. Unconsolidated deposits at the site are diverse in lithologic character and are spatially and stratigraphically complex. Thickness of these Quaternary deposits ranges from 3 to 27 meters and averages 17 meters. The unconsolidated deposits overlay 140 meters of Pennsylvanian shale, mudstone, siltstone, and coal. Approximately 90,500 cubic meters of waste were buried from August 1967 through August 1978, in 21 trenches that were constructed in glacial materials by using a cut-and-fill process. Trenches generally were constructed below grade and ranged from 11 to 180 meters long, 2.4 to 21 meters wide, and 2.4 to about 7.9 meters deep. Research on microclimate and evapotranspiration at the site was conducted from July 1982 through June 1984. Continuous measurements were made of precipitation, incoming and reflected solar (shortwave) radiation, incoming and emitted terrestrial (longwave) radiation, horizontal windspeed and direction, wet- and dry-bulb air temperature, barometric pressure, soil-heat fluxes, and soil temperature. Soil-moisture content, for this research phase, was measured approximately biweekly. Evapotranspiration rates were estimated by using three techniques--energy budget, aerodynamic profile, and water budget. Although monthly totals for each method differed, estimated annual evapotranspiration averages ranged from 630 to 693 millimeters or about 70 percent of precipitation. Tritium concentrations in leaf water from on-site plants were determined for 125 vegetation samples collected during the summers of 1982 through 1986. Concentrations varied significantly among some locations and plant types. Tritium concentrations ranged from the detection limit of 0 .2 to 1,330 nanocuries per liter, with alfalfa (Medicago sativa) having the highest concentrations, followed by brome grass (Bromus inermis), and then red clover (Trifoleum pratense); these variations in concentration are most likely a result of root depth. Runoff and sediment transport were measured from July 1982 through December 1985 in four basins--three comprising almost two-thirds of the 8.1-hectare site and one comprising a 1.4-hectare undisturbed area. Volumes and equivalent weights of collapses were estimated from records of site surficial conditions from October 1978 through December 1985. Runoff showed a direct relation to degree of land modification; lowest mean yields were measured at the undisturbed area, and highest mean yields were measured from the basin composed wholly of trench and intertrench areas. Sediment yield measured onsite averaged 3.4 megagrams per hectare. A total of 315 collapse cavities, corresponding to a cumulative volume of about 500 cubic meters, were documented. Most collapses were recorded after periods of rainfall or snowmelt when soil moisture was near maximum. Almost two-thirds of the collapses, corresponding to 63 percent of the cumulative cavity volume, occurred during February through April. Data for the study of water movement through a trench cover were collected from July 1982 through June 1934. Pressure-head data were collected at four different clusters at depths ranging from 50 to 1,850 millimeters within a selected trench cover. Soil-moisture content for this research phase was measured weekly with a gamma-attenuation moisture probe. The amount of water stored within the trench cover fluctuated in an annual cycle. Moisture contents were greatest in late March or early April, decreased steadily from late spring through the summer, reached a minimum in late August or early September, and then increased gradually from midfall through the winter. Depths of wetting-front movements were a function of initial soil-moisture content and total storm precipitation. Seepage to the trench was estimated by use of four different methods: the Darcy method, the zero-flux phase method, the surface-based water-budget method, and the ground-water based water-budget method. Estimates by the different methods differed considerably. Investigation of the unsaturated zone at the site began in 1981 and is ongoing (1987). Water movement was measured along a generalized vertical section through four trenches. A 120-meter-long, 2-meter-diameter horizontal tunnel provided access below the trenches. The timing of water movement varied temporally and spatially. Vertical flow was inhibited at interfaces between lithologic units of contrasting hydraulic conductivities. Data also indicate that water movement through the sand of the Toulon Member of the Glasford Formation occurs along localized partially saturated to saturated flow paths. Average velocities of water movement through the extent of the unsaturated zone, as estimated by a saturation-tracking method, ranged from 0.04 to 0.34 meter per day. Tritium concentrations in the unsaturated zone varied spatially reflecting the heterogeneity of wastes in the overlying trenches and local hydrogeologic conditions. Tritium concentrations at all lysimeter locations increased with time; however, the increases usually were of small magnitude. Tritium concentrations increased abruptly, from five to nine times previous concentrations, at only 3 of 14 locations. Gas samples were collected from a network of soil-gas piezometers located in the undisturbed unsaturated zone near a waste trench at approximately 70-day intervals during 1984-86. Relative proportions of nitrogen, oxygen plus argon, carbon dioxide, methane, ethane, propane, butane, tritiated water vapor, carbon dioxide, and 222radon were converted to partial pressures, based on a mean atmospheric pressure of 98.6 kilopascals. Methane and 14 carbon dioxide were identified as originating in the waste and having mean partial pressures that generally decreased with horizontal distance from the trench and with vertical distance to the land surface. Partial-pressure gradients for other radioactive gases were not detected in the gas sampling network; definable gradients may occur much nearer to the waste source. Ground-water flow has been studied at the site since 1976. The spatial, stratigraphic, and lithologic complexity of the unconsolidated deposits that compose the shallow aquifer result in the free water surface intersecting nine different lithologic units at the site. Saturated hydraulic conductivities of these units range from about 4x10-12 to 8x10-6 centimeters per second. Three ground-water basins were defined within the shallow aquifer, with flow generally from west to east. Ground-water velocities are highly variable. A tracer test conducted in a pebbly-sand unit resulted in velocities in the range of 640 to 770 meters per year. Estimated velocities for the other units ranged from 2 to 490 meters per year. Tritium was detected in observation wells on-site in 1976 and off-site in 1982. Concentrations ranged from the analytical detection limit of 0.2 to over 300 nanocuries per liter. Seasonal variations in tritium concentrations were observed in most wells, and dilution caused by infiltrating rainfall was observed. Water-chemistry research included the collection and analysis of precipitation, geologic materials, and unsaturated- and saturated-zone water, both on-site and off-site, and in all geologic units, during 1978 to 1984. Precipitation was a calcium-zinc-sulfate type water. Calcium and bicarbonate were the most abundant cation and anion, respectively, in the geologic materials. Mean dissolved organic carbon and tritium concentrations (45 milligrams per liter and 290 nanocuries per liter, respectively) were greater in samples from six lysimeters located directly below waste trenches and one located within a trench, than in samples from all other lysimeters (8.4 milligrams per liter and 17 nanocuries per liter, respectively). Water in the saturated zone was generally a magnesium-bicarbonate type. Tritium was the only radionuclide detected in the saturated zone.