Geology topics

Mark Vendl

Publications and source records attributed to Mark Vendl.

3 recordsLinked to original sources

USGS2004

A cross-site comparison of methods used for hydrogeologic characterization of the Galena-Platteville aquifer in Illinois and Wisconsin, with examples from selected Superfund sites

The effectiveness of 28 methods used to characterize the fractured Galena-Platteville aquifer at eight sites in northern Illinois and Wisconsin is evaluated. Analysis of government databases, previous investigations, topographic maps, aerial photographs, and outcrops was essential to understanding the hydrogeology in the area to be investigated. The effectiveness of surface-geophysical methods depended on site geology. Lithologic logging provided essential information for site characterization. Cores were used for stratigraphy and geotechnical analysis. Natural-gamma logging helped identify the effect of lithology on the location of secondary- permeability features. Caliper logging identified large secondary-permeability features. Neutron logs identified trends in matrix porosity. Acoustic-televiewer logs identified numerous secondary-permeability features and their orientation. Borehole-camera logs also identified a number of secondary-permeability features. Borehole ground-penetrating radar identified lithologic and secondary-permeability features. However, the accuracy and completeness of this method is uncertain. Single-point-resistance, density, and normal resistivity logs were of limited use. Water-level and water-quality data identified flow directions and indicated the horizontal and vertical distribution of aquifer permeability and the depth of the permeable features. Temperature, spontaneous potential, and fluid-resistivity logging identified few secondary-permeability features at some sites and several features at others. Flowmeter logging was the most effective geophysical method for characterizing secondary-permeability features. Aquifer tests provided insight into the permeability distribution, identified hydraulically interconnected features, the presence of heterogeneity and anisotropy, and determined effective porosity. Aquifer heterogeneity prevented calculation of accurate hydraulic properties from some tests. Different methods, such as flowmeter logging and slug testing, occasionally produced different interpretations. Aquifer characterization improved with an increase in the number of data points, the period of data collection, and the number of methods used.

Scientific Investigations Report↗

USGS1999

Geology, hydrology, and results of tracer testing in the Galena-Platteville aquifer at a waste-disposal site near Byron, Illinois

A study was conducted by the U.S. Geological Survey and the U.S. Environmental Protection Agency of the geohydrology of the dolomite bedrock at a waste-disposal site near Byron, Illinois. The study was designed to identify and characterize the flow pathways through the bedrock aquifer beneath the site. The geologic units of concern at the site are the Glenwood Formation of the Ancell Group, and the Platteville and Galena Groups. These deposits compose the Galena-Platteville aquifer and the underlying Harmony Hill Shale semiconfining unit. The Galena-Platteville aquifer is an unconfined aquifer. Geophysical logging, water levels, and aquifer-test data indicate the presence of interconnected, hydraulically active fractures in the middle of the Galena-Platteville aquifer (the upper flow pathway), and a second set of hydraulically active fractures (the lower flow pathway). The lower flow pathway may be present through much of the site. Few hydraulically active fractures are present in the upper part of the aquifer near the center of the site, but appear to be more numerous in the upper part of the aquifer in the western and northeastern parts of the site. Water-level data obtained during the tracer test indicate that pumping effects were present near the pumped wells. Pumping effects may have been present at several wells located along directions of identified fracture orientation from the pumped well. The upper part of the aquifer did not appear to be hydraulically well connected to the flow pathways supplying water to the pumped well. Large background changes in water levels obscured the effects of pumping and prevented calculation of aquifer properties. The velocity of the bromide tracer through the lower flow pathway under the hydraulic gradient resulting from the pumping was about 152 feet per day. Solution of the Darcy velocity equation results in a calculated effective porosity for this interval of 3.5 percent, indicating hydraulic interconnection between the fractures and the aquifer matrix. Ground-water velocity through the lower flow pathway was calculated to be 15.4 feet per day under hydrostatic conditions.

Illinois↗

USGS1998

Use of borehole-radar methods to monitor the movement of a saline tracer in carbonate rock at Belvidere, Illinois

Common-depth (CD) radar surveys and cross-hole radar tomography methods were used to monitor the movement of a saline tracer in a dual-porosity dolomite aquifer at Belvidere, Illinois. The tracer test was conducted using an array of six open-hole bedrock wells at the Parson’s Casket Hardware Superfund site. The injection and recovery boreholes were about 20 m (meters) apart, and the imaging boreholes were arranged to provide planar coverage across and along the anticipated tracer path. A hydraulically conductive zone identified during previous investigations was isolated using straddle packers and pumped to establish a hydraulic gradient between the injection and recovery wells. A sodium chloride (NaCl) solution was continuously injected into this zone to move the tracer across the tomographic image plane. CD cross-hole radar surveys and cross-hole tomography surveys were conducted before and periodically during the tracer injection. Background tomograms contain similar radar velocity and attenuation changes with depth, consistent with a layered dolomite that has variable porosity and electrical conductivity. Slow changes in attenuation associated with low tracer velocity permitted the acquisition of multiple CD surveys and two cross-hole tomography surveys during injection. CD surveys were used to rapidly identify the presence of tracer between wells. Attenuation-difference tomograms contain attenuation increases that delineate the spatial distribution with time of the saline tracer and show the progressive movement of the tracer within the tomographic image plane. Formation porosity and resistivities calculated from radar velocity and attenuation tomograms were used to estimate changes in fluid resistivity and tracer concentration in the tomographic image plane.

Illinois↗