USGS Science⌕ Search

Geology topics

G. N. Delin

Publications and source records attributed to G. N. Delin.

At least 37 records · Page 2Linked to original sources
USGS1998

Ground water contamination by crude oil near Bemidji, Minnesota

Ground-water contamination by crude oil, and other petroleum-based liquids, is a widespread problem. An average of 83 crude-oil spills occurred per year during 1994-96 in the United States, each spilling about 50,000 barrels of crude oil (U.S. Office of Pipeline Safety, electronic commun., 1997). An understanding of the fate of organic contaminants (such as oil and gasoline) in the subsurface is needed to design innovative and cost-effective remedial solutions at contaminated sites.

Minnesota↗
USGS1998

Spatial variation in saturated hydraulic conductivity of sediments at a crude-oil spill site near Bemidji, Minnesota

Saturated hydraulic conductivity of aquifer sediments at a crude-oil spill research site near Bemidji, Minnesota were examined using pneumatically-induced head-difference tests and packer/vacuum system tests. Results from slug tests on 58 wells show that hydraulic conductivity varies both horizontally and vertically in the range from about 10 -7 to 10 -4 meters per second (m/s), with a median of 7.28 x 10 -5 m/s. Hydraulic conductivities of the well-sorted medium to fine sand facies, which contains a majority of the oil plume, range from 1.76 x 10 -5 to 9.82 x 10 -5 m/s with a median of 5.42 x 10 -5 m/s. Hydraulic conductivities of the lower sand and gravel unit, which contains a majority of the plume of dissolved petroleum constituents, range from 4.42 x 10 -6 to 5.36 x 10 -4 m/s with a median of 2.32 x 10 -4 m/s. The average linear velocity of ground water near the spill site was calculated to examine the effects of advective flow on migration of the plumes of oil and dissolved petroleum constituents. The average linear velocity in the well-sorted medium to fine sand facies during September 1996 was about 11 meters per year (m/year). If we assume that this was the average velocity during the 17-year period since the spill (1979-96), total advective flow of ground water in this facies was about 187 m. During this 17-year period, oil floating on the water table migrated only about 40 m. By comparison, the lower sand and gravel unit had an average linear velocity of about 29 m/year, or about 3 times greater than the velocity in the well-sorted medium to fine sand facies. Based on a 29 m/year velocity, advective flow of ground water in this unit during the 17-year period since the spill was about 493 m; whereas, the plume of dissolved petroleum constituents migrated only about 200 m. These results indicate that spatial variability of hydraulic conductivity and ground-water velocity at the research site likely is a factor affecting the rate of contaminant migration. Additional research is needed to fully evaluate how the contaminant plumes are affected by changes in hydraulic properties of the various lithologic units.

Minnesota↗
USGS1998

Effects of farming systems on ground-water quality at the management systems evaluation area near Princeton, Minnesota, 1991-95

Ground-water quality in an unconfined sand and gravel aquifer was monitored during 1991-95 at the Minnesota Management Systems Evaluation Area (MSEA) near Princeton, Minnesota. The objectives of the study were to: (1) describe the effects of three farming systems on groundwater quality, and (2) evaluate the factors affecting ground-water quality and transport of agricultural chemicals at the site. Concentrations of nitrate nitrogen (nitrate-N) in the upper 1 meter (m) of the saturated zone were greatest beneath the two cropped areas having a potato-sweet corn annual rotation (median concentrations of 23 and 22 mg/L). Concentrations of nitrate-N were least beneath a cropped area having a field cornsoybean annual rotation (median of 14 mg/L); another cropped area having the field corn-soybean rotation had similar nitrate-N concentrations to those beneath a cropped area having field corn in consecutive years (continuous corn)(medians of 17 mg/L). Concentrations of atrazine plus metabolites de-ethylatrazine (DEA) and de-isopropylatrazine (DIA), atrazine plus metabolites, were significantly greater during 1994-95 than during 1992- 93 beneath all cropped areas in the upper 1 m of the saturated zone. Concentrations of atrazine plus metabolites during 1994-95 were greatest beneath the continuous corn (median of 1.07 ( μ g/L), intermediate beneath one cropped area with the potato-sweet corn rotation (median of 0.37 μ g/L), and least beneath the other cropped area with the potato-sweet corn rotation, the field corn-soybean rotation, and background areas (medians ranging from 0.11 to 0.21 μ g/L), for which concentrations were not significantly different. Concentrations of atrazine plus metabolites during 1992-93 were mostly similar beneath the different cropped areas and background areas. DEA was the predominant atrazine-metabolite detected in ground water; the average DEA to atrazine ratio was 8.0. The herbicides metribuzin, alachlor, and metolachlor were rarely detected in ground water at trace levels and could not be linked to the MSEA farming systems, with the exception of metribuzin detections during 1993-94 at concentrations of 0.14-1.24 ( μ g/L beneath one cropped area where metribuzin was applied to potatoes. Peak concentrations of chloride and bromide tracers were usually detected in the upper 2 m of the saturated zone 11 to 19 months after application. Peak concentrations of nitrate-N and atrazine plus metabolites were usually detected about 13 to 27 months and 2 years after application, respectively. The estimated proportion of applied nitrogen that reached ground water ranged from about 13 to 50 percent with an average of 30 percent. Differences in the concentrations of nitrate-N in ground water between different cropped areas were related to varying nitrogen application rates, timing of nitrogen application, timing of recharge in relation to crop rotation, and differences in nitrogen uptake by crops. In order of importance, plant uptake and leaching to ground water likely account for most of the nitrogen applied. Denitrification likely is an important mechanism affecting nitrate-N concentrations at depths greater than 2 m below the water table. The proportion of applied atrazine in ground water, detected as atrazine or its metabolites, ranged from 0 to about 1 percent with an average of 0.37 percent. The small proportion of applied atrazine detected in ground water indicates that atrazine was predominantly affected by processes occurring in the soil such as adsorption and degradation. Concentrations of atrazine plus metabolites were related to application rates.

Minnesota↗
USGS1997

Hydrogeologic and water-quality data used to evaluate the effects of focused recharge on ground-water quality near Princeton, Minnesota, 1991-95

This study was part of the Management Systems Evaluation Area (MSEA) Program, a multi-scale, inter-agency initiative to evaluate the effects of agricultural systems on water quality in the midwest corn belt. The research was part of the U.S. Geological Survey Toxics Substances Hydrology Program. The research area was located in the Anoka Sand Plain about 5 kilometers southwest of Princeton, Minnesota. This report presents temperature, precipitation, soil-moisture, water-quality, and other data collected during 1991-95 to evaluate the effects of focused recharge on ground-water quality at the Princeton MSEA.

Minnesota↗
USGS1997

Water-quality and hydrogeologic data used to evaluate the effects of farming systems on ground-water quality at the Management Systems Evaluation Area near Princeton, Minnesota, 1991-95

The Minnesota Management Systems Evaluation Area (MSEA) project was part of a multi-scale, inter-agency initiative to evaluate the effects of agricultural management systems on water quality in the midwest corn belt. The research area was located in the Anoka Sand Plain about 5 kilometers southwest of Princeton, Minnesota. The ground-water-quality monitoring network within and immediately surrounding the research area consisted of 73 observation wells and 25 multiport wells. The primary objectives of the ground-water monitoring program at the Minnesota MSEA were to: (1) determine the effects of three farming systems on ground-water quality, and (2) understand the processes and factors affecting the loading, transport, and fate of agricultural chemicals in ground water at the site. This report presents well construction, geologic, water-level, chemical application, water-quality, and quality-assurance data used to evaluate the effects of farming systems on ground-water quality during 1991-95.

Minnesota↗
USGS1996

Analysis of hydrogeologic properties in the Prairie du Chien-Jordan aquifer, Shakopee Mdewakanton Sioux Community, southeastern Minnesota

The Prairie du Chien-Jordan aquifer is a major source of water for many communities in southeastern Minnesota. The water-supply well for the Shakopee Mdewakanton Sioux Community derives water from the Jordan part of the aquifer. An aquifer test in the Prairie du Chien-Jordan aquifer in the area of the Shakopee Mdewakanton Sioux Community was completed in November 1995. The test consisted of pumping water from a public works well open to the Jordan part of the aquifer and measuring drawdown in this well and two observation wells. This was followed by measuring recovery in the wells after the pumping was terminated. The Neuman (1974) method for unconfined aquifers was used to analyze data collected from the two observation wells during the drawdown and recovery periods, resulting in a range of estimated aquifer hydraulic properties. Aquifer transmissivity ranged from 4,710 to 7,660 ft 2 /d and aquifer storativity ranged from 8.24 x 10 -5 to 1.60 x 10 -4 . These values are generally in close agreement for all four sets of data, given the limitations of the test, indicating that the test results are accurate and representative of the aquifer hydrogeologic properties. The lack of late-time data made it impossible to accurately assess aquifer specific yield.

Minnesota↗
USGS1995

Ground-water quality in agricultural areas, Anoka Sand Plain Aquifer, east-central Minnesota, 1984-90

Ground-water quality in the Anoka Sand Plain aquifer was studied as part of the multiscale Management Systems Evaluation Area (MSEA) study by collecting water samples from shallow wells during August through November 1990. The sampling was conducted to: (1) aid in selection of the MSEA research area; (2) facilitate comparison of results at the MSEA research area to the regional scale; and (3) evaluate changes in ground-water quality in the Anoka Sand Plain aquifer since a previous study during 1984 through 1987. Samples were collected from 34 wells screened in the upper 6 meters of the surficial aquifer and located in cultivated agricultural areas. Water temperature, pH, specific conductance, and presence or absence of triazine herbicides were determined at all sites and samples from selected wells were analyzed for concentrations of dissolved oxygen, alkalinity, major cations and anions, nutrients, and selected herbicides and herbicide metabolites. The results of the study indicate that the water-quality of some shallow ground water in areas of predominantly agricultural land use has been affected by applications of nitrogen fertilizers and the herbicide atrazine. Concentrations of nitrite plus nitrate nitrogen (nitrate-N) in 19 samples ranged from less than the detection limit of 0.1 to 21 milligrams per liter (mg/L) with a median of 10 mg/L. Concentrations of nitrate-N were not significantly correlated with depth below the water table or dissolved oxygen but were significantly correlated with concentrations of chloride. Concentrations of nitrate-N during 1990 were generally similar to concentrations measured during 1984 through 1987. Changes in concentrations of nitrate-N during 1984 through 1990 were likely related to variations in recharge or other site-specific factors. Immunoassay analyses were used as screening tools to detect the presence of triazine herbicides. All samples in which triazine herbicides were detected by immunoassay, and selected samples in which triazine herbicides were not detected by immunoassay, were analyzed for selected herbicides and herbicide metabolites by gas chromatography/mass spectroscopy (GC/MS). There was an excellent correspondence between concentrations of triazine herbicides indicated by immunoassay and concentrations of atrazine measured by GC/MS, indicating that the immunoassay method was a valuable qualitative to semi-quantitative tool for evaluating the presence and approximate concentration of atrazine. The combined results of immunoassay and GC/MS analyses indicate that atrazine was detected in 11 of the 34 wells with a median concentration less than the immunoassay detection limit of 0.1 micrograms per liter ( μ g/L). Atrazine was detected in 11 of the 17 samples analyzed by GC/MS at concentrations ranging from the detection limit of 0.05 to 0.81 μ g/L with a median of 0.09 μ g/L. Atrazine metabolite de-ethylatrazine (DEA) was the most frequently detected herbicide or herbicide metabolite and generally was present at the greatest concentrations. There were detections of DEA in 13 of the 17 samples analyzed at concentrations ranging from the detection limit of 0.05 to 1.12 μ g/L with a median of 0.15 μ g/L. Concentrations of DEA were significantly correlated with concentrations of calcium, magnesium, and specific conductance. The atrazine metabolite de-isopropylatrazine and the herbicide metolachlor both were detected in 1 of the 17 wells. The frequency of detection and the concentrations of atrazine in shallow ground water during 1990 were very similar to results of sampling conducted in 1984. Concentrations of atrazine and DEA generally were greater near the water table and decreased or were not detected in deeper wells. All of the samples in which atrazine and DEA were detected also had increased (greater than 3 mg/L) nitrate-N concentrations. However, not all samples with increased concentrations of nitrate-N had detections of atrazine or DEA. This likely indicates either that there were sources of nitrate-N other than cultivated fields on which both atrazine and nitrogen were applied or that nitrate-N reached ground water more readily than atrazine or DEA.

Minnesota↗
USGS1995

Effects of 1992 farming systems on ground-water quality at the management systems evaluation area near Princeton, Minnesota

The Management Systems Evaluation Area (MSEA) program was a multiscale, interagency initiative to evaluate the effects of agricultural systems on water quality in the midwest corn belt. The primary objective of the Minnesota MSEA was to evaluate the effects of ridge-tillage practices in a corn and soybean farming system on ground-water quality. The 65-hectare Minnesota MSEA was located in the Anoka Sand Plain near the town of Princeton, Minnesota. Three fanning systems were evaluated: corn-soybean rotation with ridge-tillage (areas B and D), sweet corn-potato rotation (areas A and C), and field corn in consecutive years (continuous corn; area E). Water samples were collected four different times per year from a network of 22 multiport wells and 29 observation wells installed in the saturated zone beneath and adjacent to the cropped areas. Bromide and chloride were used as tracers of water recharged through the cropped areas during 1992. Bromide applied in May 1992 was first detected above background levels between August 1992 and April 1993. Thus, the time of travel of water and bromide moving through the unsaturated zone during 1992 ranged from 3 to 11 months. Chloride applied to area C (sweet corn) in April 1992 was first detected above the residual levels of 1991 chloride applications in April 1993, 12 months after the chemical was applied. Chloride applies to areas A, B, D, and E in April 1992 was not detected above the residual effects from 1991 chloride applications. Nitrogen (N) fertilizer applied in 1992 on area C (potatoes) was first detected above background concentrations and the residual effects of the 1991 farming practices in April 1993, 12 months after application. Effects of 1992 N fertilizer applications on area E (continuous com) generally could not be distinguished from the effects of downgradient of area E were consistently greater than background concentrations during August 1992 through April 1993. These concentrations greater than background levels indicate that some N fertilizer applied to the continuous com crop during 1991 reached the water table. Nitrogen fertilizer applied on areas A, B, and D during 1992 could not be distinguished from the residual effects of the 1991 fanning practices but were detected above background concentrations. Atrazine concentrations beneath the cropped areas were generally indistinguishable from background concentrations. Atrazine was detected in 58 percent of the 361 ground water samples collected beneath cropped and buffer areas during June 1992 through April 1993. Most detections were at trace levels, between the detection limit of 0.01 micrograms per liter ( μ g/L) and the reporting limit of 0.04 μ g/L. De-ethylatrazine (DEA) was detected more frequently during June 1992 through April 1993 (78 percent of the 361 samples) and in greater concentrations than any other herbicide or herbicide metabolite, with a median concentration of 0.07 μ g/L. The maximum DEA concentration of 0.77 μ g/L was detected near the water table in the middle of area E (continuous corn) during April 1993. The likely source of this DEA detection was application of atrazine to area E during 1991-93. Additional data will be needed to conclusively evaluate whether atrazine applied as part of the MSEA farming systems reached the water table. Results indicate that the effects of the 1992 potassium-chloride and N fertilizer applications were reduced compared to the effects of 1991 applications. The most important factors associated with these differences were lower chemical application rates and lower recharge rates during 1992 than during 1991. Some of the chloride and N fertilizer applied to the cropped areas in 1992 likely did not reach the saturated zone in 1993 due to a 60-percent reduction in recharge compared to 1991. Therefore, analysis of data from additional years will be required to fully evaluate the effects of the fanning systems on ground-water quality.

Minnesota↗
USGS1994

Cyclic injection, storage, and withdrawal of heated water in a sandstone aquifer at St. Paul, Minnesota: Analysis of thermal data and nonisothermal modeling of short-term test cycles

In May 1980, the University of Minnesota began a project to evaluate the feasibility of storing heated water (150 degrees Celsius) in the Franconia-Ironton-Galesville aquifer (180 to 240 meters below land surface) and later recovering it for space heating. The University's steam-generation facilities supplied high-temperature water for injection. The Aquifer Thermal-Energy Storage system is a doublet-well design in which the injection-withdrawal wells are spaced approximately 250 meters apart. Water was pumped from one of the wells through a heat exchanger, where heat was added or removed. This water was then injected back into the aquifer through the other well. Four short-term test cycles were completed. Each cycle consisted of approximately equal durations of injection and withdrawal ranging from 5.25 to 8.01 days. Equal rates of injection and withdrawal, ranging from 17.4 to 18.6 liters per second, were maintained for each short-term test cycle. Average injection temperatures ranged from 88.5 to 117.9 degrees Celsius. Temperature graphs for selected depths at individual observation wells indicate that the Ironton and Galesville Sandstones received and stored more thermal energy than the upper part of the Franconia Formation. Clogging of the Ironton Sandstone was possibly due to precipitation of calcium carbonate or movement of fine-grain material or both. Vertical-profile plots indicate that the effects of buoyancy flow were small within the aquifer. A three-dimensional, anisotropic, nonisothermal, ground-water-flow, and thermal-energy-transport model was constructed to simulate the four short-term test cycles. The model was used to simulate the entire short-term testing period of approximately 400 days. The only model properties varied during model calibration were longitudinal and transverse thermal dispersivities, which, for final calibration, were simulated as 3.3 and 0.33 meters, respectively. The model was calibrated by comparing model-computed results to (1) measured temperatures at selected altitudes in four observation wells, (2) measured temperatures at the production well, and (3) calculated thermal efficiencies of the aquifer. Model-computed withdrawal-water temperatures were within an average of about 3 percent of measured values and model-computed aquifer-thermal efficiencies were within an average of about 5 percent of calculated values for the short-term test cycles. These data indicate that the model accurately simulated thermal-energy storage within the Franconia-Ironton-Galesville aquifer.

Open-File Report↗
USGS1994

Hydrogeologic and water-quality data used to characterize the Management Systems Evaluation Area near Princeton, Minnesota, 1991

The Minnesota Management Systems Evaluation Area project is part of a multi-scale, inter-agency initiative to evaluate the effects of agricultural management systems on water quality in the midwest corn belt. The research area is located in the Anoka Sand Plain about 5 kilometers southwest of Princeton, Minnesota. The ground-water-quality monitoring network within and immediately surrounding the research area consists of 29 observation wells and 22 multiport wells. Thirteen observation wells are also located outside the research area. The primary objectives of research by the U.S. Geological Survey at the Princeton Management Systems Evaluation Area are to: (1) determine the relation of the spatial and temporal distribution of agricultural chemicals in ground water to recharge, topography, and subsurface heterogeneities; and (2) determine the effects of the modified and prevailing farming systems on ground-water quality. This report presents geologic logs and water-quality data used to characterize the Princeton Management Systems Evaluation Area.

Minnesota↗
USGS1994

Characterization of the hydrogeology and water quality at the Management Systems Evaluation Area near Princeton, Minnesota, 1991-92

The Management Systems Evaluation Area (MSEA) program is part of a multi-scale, inter-agency initiative to evaluate the effects of agricultural management systems on water quality in the midwest corn belt. The Minnesota MSEA project is one of five projects selected to represent the principal hydrogeologic settings and geographic diversity of prevailing management systems in the midwest corn belt. The Minnesota MSEA research area is located in the Anoka Sand Plain about 5 kilometers southwest of Princeton, Minnesota. The water-quality monitoring network within the 65-hectare research area consists of 29 observation wells and 22 multiport wells. Thirteen observation wells also are located outside the research area. Glacial deposits beneath the research area generally consist of fine to medium sand in the unsaturated zone and coarse to very coarse sand and gravel in the saturated zone. The average depth to the water table is about 3.6 meters below land surface. Ground-water recharge during 1992 was lower (4.9-13.2 centimeters) than during 1991 (11.7-25.7 centimeters) because of reduced precipitation (58.5 centimeters during 1992 and 94.5 centimeters during 1991). Estimates of saturated horizontal hydraulic conductivity for the surficial aquifer were made using five methods. Results were within about two orders of magnitude and also agree favorably with estimates from a previous study of the Anoka Sand Plain. The smallest hydraulic conductivities were obtained using laboratory analyses (0.0052 centimeters per second) and the largest estimate was obtained from results of an aquifer test (0.2820 centimeters per second). The estimate of hydraulic conductivity based on the time of travel of chloride (0.0655 centimeters per second) is considered most accurate and representative of the surficial aquifer in the research area. Anthropogenic effects of previous land use were detected in water samples collected during April 1991, prior to implementation of the MSEA farming systems. Concentrations of nitrate-nitrogen (nitrate-N) in the surficial aquifer equaled or exceeded the U.S. Environmental Protection Agency's recommended maximum contaminant level of 10 milligrams per liter (mg/L) in 4 of the 7 wells in the research area. The maximum concentration of nitrate-N in ground water from these wells was 23 mg/L with a median of 10 mg/L. The median concentration of nitrate-N for these wells exceeded the median in wells located upgradient from the research area (2.1 mg/L). Similarly, the median concentration of chloride from wells in the research area (11 mg/L) exceeded the median in upgradient wells (3.8 mg/L). On-site sources of the elevated nitrate-N include decomposition of alfalfa, grown on-site during 1981-89, and application of nitrogen fertilizer to corn during 1990. A likely on-site source of the elevated chloride is application of potassium-chloride fertilizer to crops prior to 1991. Atrazine was detected by gas chromatography mass spectroscopy in 2 of the 7 wells in the research area at concentrations of 0.04 and 0.17 micrograms per liter (ug/L), well below the U.S. Environmental Protection Agency's recommended maximum contaminant level of 3 ug/L. The median concentration in these Wells was less than the qualitative detection limit of 0.01 ug/L. Atrazine metabolite de-ethylatrazine was the most frequently detected herbicide or herbicide metabolite. De-ethylatrazine was detected in 5 of the 7 wells in the research area at concentrations ranging from 0.12 to 0.32 ug/L with a median concentration of 0.14 ug/L. Atrazine metabolite de-isopropylatrazine was not detected above the qualitative detection limit of 0.06 ug/L. The most likely sources of atrazine are applications to the research area during 1990 or from precipitation.

Minnesota↗
USGS1993

Effects of focused recharge on the transport of agricultural chemicals at the Princeton, Minnesota Management Systems Evaluation Area, 1991-92

Rates of water movement through the unsaturated zone greatly affect the amount and concentrations of agricultural chemicals that may reach the water table. For example, recharge can flush chemicals to the water table which have accumulated in the unsaturated zone during dry periods. A better understanding of how topography influences recharge and the movement of agricultural chemicals is needed. In 1991, the U.S. Geological Survey (USGS), with funding from the USGS Toxic Substances Hydrology Program, began studying the movement of water and agricultural chemicals to the water table at the Management Systems Evaluation Area (MSEA) near Princeton, Minnesota. The primary objective of this four-year research study is to evaluate the effects of transient recharge, topography, and subsurface heterogeneities on the flux of water and agricultural chemicals to ground water. To achieve this objective the approach was to (1) install instruments to sample and measure the movement of water through the unsaturated zone beneath topographically high and low areas of a corn field; (2) conduct recharge and tracer tests in the field to evaluate the movement of water and agricultural chemicals at both topographic settings; and (3) simulate the field recharge and tracer tests in the laboratory. The primary research hypothesis was that the vertical flux of water and agricultural chemicals is greater in topographically low areas than in topographically high areas.

Minnesota↗
USGS1993

Effects of recharge on the transport of agricultural chemicals at the Princeton, Minn. Management Systems Evaluation Area (MSEA), 1991-92

Rates of water movement through the unsaturated zone greatly affect the amount and concentrations of agricultural chemicals that may reach the water table. For example, recharge can flush to the water table chemicals that have accumulated In the unsaturated zone during dry periods. A better understanding of how topography influences recharge and the movement of agricultural chemicals is needed. In 1991, the U.S. Geological Survey (USGS), with funding from the USGS Toxic Substances Hydrology Program, began studying the movement of water and agricultural chemicals to the water table at the Management Systems Evaluation Area (MSEA) near Princeton, Minnesota. Instruments were installed to measure the movement of moisture through the soil beneath a corn field. Samples of the recharge water were analyzed for concentrations of agricultural chemicals and tracers. Field recharge and tracer tests were simulated In the laboratory.

Minnesota↗
USGS1993

Field observations, preliminary model analysis, and aquifer thermal efficiency

In May 1980, the University of Minnesota began a project to evaluate the feasibility of storing heated (150 degrees Celsius (°C) water in the deep (180 to 240 meters (m)) Franconia-Ironton-Galesville aquifer and later recovering it for space heating. The Aquifer Thermal-Energy Storage (ATES) system was a doublet-well design in which the injection and withdrawal wells were spaced approximately 250 m apart. High-temperature water from the university's steam-generation facilities supplied heat for injection. Water was pumped from one of the wells through a heat exchanger, where heat was added or removed. Water then was injected back into the aquifer through the other well. The experimental plan for testing the ATES system consisted of a series of short-term hot-water injection, storage, and withdrawal cycles. Each cycle was 24 days long, and each injection, storage, and withdrawal step of the cycle was 8 days. The Franconia-Ironton-Galesville aquifer is a consolidated sandstone, approximately 60 m thick, the top of which is approximately 180 m below the land surface. It is confined above by the St. Lawrence Formation a dolomitic sandstone 8 m thick and below by the Eau Claire Formation a shale 30 m thick. Initial hydraulic testing with inflatable packers indicated that the aquifer has four hydraulic zones with distinctly different values of relative horizontal hydraulic conductivity. The thickness of each zone was determined by correlating data from geophysical logs, core samples, and the inflatable-packer tests. A comprehensive network for data collection, storage, and analysis was designed to monitor temperature and pressure changes during the ATES test cycles. A total of 22 pressure transducers and 56 thermocouples monitored pressures and temperatures in the aquifer and in the upper and lower confining units. Temperature and pressure measurements were collected in observation well nests at distances of approximately 7 and 14 m from the production wells. All pressure and temperature data were transmitted through buried cables to a central data logger, where the measurements were viewed independently or stored on computer magnetic tape for later analysis. Interactive computer programs were available to display data stored on magnetic tapes as individual measurements or as plots of pressure and temperature versus time. Analyses of step-drawdown and constant-discharge aquifer tests indicate that the Franconia-Ironton-Galesville aquifer is anisotropic in the horizontal plane. Major and minor transmissivities are 101.5 and 44.6 m 2 /d (square meters per day), respectively, for the Ironton and Galesville Sandstones and 40.0 and 24.0 m 2 /d, respectively, for the upper part of the Franconia Formation. The average transmissivity of the entire Franconia-Ironton-Galesville aquifer is about 98 m 2 /d. Effective porosity ranges from 0.25 to 0.31, and the average storage coefficient is 4.5x10 -5 . Two computer models were constructed to simulate the movement of ground water and heat. The first was a nonisothermal, isotropic, single-phase, radial, ground-water flow and thermal-energy-transport model that was constructed to examine the sensitivity of model results to various hydraulic and thermal properties. The model also was used to study the potential for buoyancy flow within the aquifer and the effect of various cyclic injection and withdrawal schemes on the relative thermal efficiency of the aquifer. The second model was a threedimensional ground-water flow and thermal-energy-transport model that was constructed to incorporate the anisotropy of the aquifer. In the first model, the sensitivity analysis assumed 8 days of injection of 150°C water at 18.9 liters per second (L/s), 8 days of storage, and 8 days of withdrawal of hot water at 18.9 L/s. The analysis indicates that, for practical ranges of hydraulic and thermal properties, the ratio of horizontal to vertical hydraulic conductivity is the least important property and thermal dispersivity is the most important property used to compute temperature and aquifer thermal efficiency. Buoyancy flow was examined for several values of hydraulic conductivity and ratios of horizontal to vertical hydraulic conductivities. For the assumed base values of hydraulic and thermal properties, buoyancy flow was negligible. The greatest simulated buoyancy flow resulted from simulations in which horizontal hydraulic conductivity was increased to ten times the base value and in which the vertical hydraulic conductivity was set equal to the horizontal hydraulic conductivity. The effects of various injection and withdrawal rates and durations on computed values of aquifer relative-thermal efficiency and final well-bore temperature were studied for five 1-year hypothetical test cycles of injection and withdrawal. The least efficient scheme was 8 months injection of 150°C water at 18.9 L/s and 4 months of withdrawal of hot water at 18.9 L/s. The most efficient scheme was obtained with 6 months of injection of 150°C water at 18.9 L/s and 6 months of withdrawal of hot water at 37.8 L/s. The hypothetical simulations indicate that the calibrated model of the doublet-well system would be a valuable tool for use by the university in selecting a highly efficient system operation. In the second model, analytical solutions of anisotropic hydraulic flow around the doublet-well system were obtained to provide fluid-flux boundary conditions around the heat-injection well in three dimensions. This information simplified simulation of the doublet-well system because only the heat injection well needed to be simulated. This second model was calibrated with data from an 8-day ambienttemperature injection test at 18.9 L/s. Boundary-flux conditions were examined for nonisothermal conditions by simulating 8 days of injection of 150°C water at 18.9 L/s. Results of simulations using both models indicate that the fluxboundary conditions are adequate for simulations of short-term heatinjection testing.

Professional Paper↗