Geology topics

D. Harper

Publications and source records attributed to D. Harper.

5 recordsLinked to original sources

USGS2003

Characterization and statistical modeling of bacterial (Escherichia coli) outflows from watersheds that discharge into Southern Lake Michigan

Two watersheds in northwestern Indiana were selected for detailed monitoring of bacterially contaminated discharges (Escherichia coli) into Lake Michigan. A large watershed that drains an urbanized area with treatment plants that release raw sewage during storms discharges into Lake Michigan at the outlet of Burns Ditch. A small watershed drains part of the Great Marsh, a wetland complex that has been disrupted by ditching and limited residential development, at the outlet of Derby Ditch. Monitoring at the outlet of Burns Ditch in 1999 and 2000 indicated that E. coli concentrations vary over two orders of magnitude during storms. During one storm, sewage overflows caused concentrations to increase to more than 10,000 cfu/100 mL for several hours. Monitoring at Derby Ditch from 1997 to 2000 also indicated that E. coli concentrations increase during storms with the highest concentrations generally occurring during rising streamflow. Multiple regression analysis indicated that 60% of the variability in measured outflows of E. coli from Derby Ditch (n = 88) could be accounted for by a model that utilizes continuously measured rainfall, stream discharge, soil temperature and depth to water table in the Great Marsh. A similar analysis indicated that 90% of the variability in measured E. coli concentrations at the outlet of Burns Ditch (n = 43) during storms could be accounted for by a combination of continuously measured water-quality variables including nitrate and ammonium. These models, which utilize data that can be collected on a real-time basis, could form part of an Early Warning System for predicting beach closures.

Environmental Monitoring and Assessment↗

USGS1993

Statistical evaluation of hydrologic conditions in the vicinity of abandoned underground coal mines around Cannelburg, Indiana

A statistical analysis of daily water-level changes in an abandoned coal mine indicates that precipitation affects the potentiometric level of the mine, independent of associated atmospheric pressure changes and changes in the water level of an overlying aquifer. The independent statistical effect of precipitation (0.99 cm of water-level change per centimeter of rainfall) is interpreted to reflect either lateral percolation from the coalbed's subcrop (1.2 km from the mine) or rapid recharge through mine-associated pathways, such as poorly plugged shafts, boreholes, or subsidence fractures. The relationship between water-level changes in the mine's voids and changes in the overlying aquifer is also statistically significant, but the regression coefficient (0.04) is an order of magnitude smaller than that for precipitation, indicating that vertical percolation (which is represented by covariance of the two aquifers) through undisturbed overburden may be less effective than the recharge associated with precipitation that bypasses the overburden. An equivalent analysis of water-level changes in an underlying unmined coalbed indicated that precipitation had a weaker direct effect (regression coefficient of 0.34, compared with 0.99), although it was still the dominant independent variable. In contrast, the effect of water-level changes in an overlying aquifer (the flooded mine itself) was relatively stronger (regression coefficient of 0.15, compared with 0.04), indicating that vertical percolation through interburden is more important at depth.

Journal of Hydrology↗

USGS1991

Application of electromagnetic techniques in survey of contaminated groundwater at an abandoned mine complex in southwestern Indiana, U.S.A.

In part of a large abandoned mining complex, electromagnetic geophysical surveys were used along with data derived from cores and monitoring wells to infer sources of contamination and subsurface hydrologic connections between acidic refuse deposits and adjacent undisturbed geologic materials. Electrical resistivity increases sharply along the boundary of an elevated deposit of pyritic coarse refuse, which is highly contaminated and electrically conductive, indicating poor subsurface hydrologic connections with surrounding deposits of fine refuse and undisturbed glacial material. Groundwater chemistry, as reflected in values of specific conductance, also differs markedly across the deposit's boundary, indicating that a widespread contaminant plume has not developed around the coarse refuse in more than 40 yr since the deposit was created. Most acidic drainage from the coarse refuse is by surface runoff and is concentrated around stream channels. Although most of the contaminated groundwater within the study area is concentrated within the surficial refuse deposits, transects of apparent resistivity and phase angle indicate the existence of an anomalous conductive layer at depth (>4 m) in thick alluvial sediments along the northern boundary of the mining complex. Based on knowledge of local geology, the anomaly is interpreted to represent a subsurface connection between the alluvium and a flooded abandoned underground mine. ?? 1991 Springer-Verlag New York Inc.

Environmental Geology and Water Sciences↗

USGS1991

Superposed deposits of thick coal on the eastern edge of the Illinois Basin and their association with underlying geologic features

Comparison of maps produced from publicly available data (drillers' logs, electrical logs and mine maps) provides a basis for inferring a deep-seated influence on the distribution of superposed deposits of thick coal (>1.4 m) in four Middle Pennsylvania (Desmoinesian Series) coal beds in three mining districts of west-central Indiana. Thick sandstone (>18 m) is common in areas between and around the mining districts, but less than 3 percent of the study area (consisting of 3200 km 2 ) is underlain by both thick coal and thick sandstone. Only thick sandstone associated with the Survant Coal Member (Linton Formation), and informally referred to by us “Survant sandstone”, exists in all of the thin-coal areas. After comparison with published maps by other authors, it is inferred that distribution of the Survant sandstone, which was deposited immediately after a long period of slow deposition associated with the Colchester Coal Member (Linton Formation), may reflect topographic expression of long-term subsidence associated with differential thinning of much deeper Silurian strata (580 m below). Although the findings of this study provide the basis for a conceptual geologic model with a hypothetical structure that is amenable to statistical testing, such analysis should be undertaken only after the data are analyzed for randomness, spatial autocorrelation, linearity and normality.

International Journal of Coal Geology↗

USGS1990

Unexpected hydrologic perturbation in an abandoned underground coal mine: Response to surface reclamation?

A reclamation project at the abandoned Blackhawk Mine site near Terre Haute, Indiana, lasted about four months and involved the burial of coarse mine refuse in shallow (less than 9 m) pits excavated into loess and till in an area of about 16 ha. An abandoned flooded underground coal mine underlies the reclamation site at a depth of about 38 m; the total area underlain by the mine is about 10 km2. The potentiometric levels associated with the mine indicate a significant (2.7 m) and prolonged perturbation of the deeper confined groundwater system; 14 months after completing reclamation, the levels began to rise linearly (at an average rate of 0.85 cm/d) for 11 months, then fell exponentially for 25 months, and are now nearly stable. Prominent subsidence features exist near the reclamation site. Subsidence-related fractures were observed in cores from the site, and such fractures may have provided a connection between the shallower and deeper groundwater systems. ?? 1990 Springer-Verlag New York Inc.

Environmental Geology and Water Sciences↗