Groundwater/surface-water (GW/SW) exchange and hyporheic processes are topics receiving increasin... more Groundwater/surface-water (GW/SW) exchange and hyporheic processes are topics receiving increasing attention from the hydrologic community. Hydraulic, chemical, temperature, geophysical, and remote sensing methods are used to achieve various goals (e.g., inference of GW/SW exchange, mapping of bed materials, etc.), but the application of these methods is constrained by site conditions such as water depth, specific conductance, bed material, and other factors. Researchers and environmental professionals working on GW/SW problems come from diverse fields and rarely have expertise in all available field methods; hence there is a need for guidance to design field campaigns and select methods that both contribute to study goals and are likely to work under site-specific conditions. Here, we present the spreadsheet-based GW/SW-Method Selection Tool (GW/SW-MST) to help practitioners identify methods for use in GW/SW and hyporheic studies. The GW/SW-MST is a Microsoft Excel-based decision support tool in which the user selects answers to questions about GW/SW-related study goals and site parameters and characteristics. Based on user input, the tool indicates which methods from a toolbox of 32 methods could potentially contribute to achieving the specified goals at the site described. This article is protected by copyright. All rights reserved.
A tracer test was conducted to aid in the investigation of water movement and solute transport at... more A tracer test was conducted to aid in the investigation of water movement and solute transport at a crude-oil spill site near Bemidji, Minnesota. Time of travel was measured using breakthrough curves for rhodamine WT and bromide tracers moving from the soil surface through oil-contaminated and oil-free unsaturated zones to the saturated zone. Results indicate that the rates of tracer movement were similar in the oil-free unsaturated and saturated zones compared to the oily zones. These results are somewhat surprising given the oil contamination in the unsaturated and saturated zones. Rhodamine tracer breakthrough in the unsaturated and saturated zones in general was delayed in comparison to bromide tracer breakthrough. Peak tracer concentrations for the lysimeters and wells in the oily zone were much greater than at the corresponding depths in the oil-free zone. Water and tracer movement in the oily zone was complicated by soil hydrophobicity and decreased oil saturations toward the...
As a part of a study of the subsurface transport and natural attenuation of petroleum hydrocarbon... more As a part of a study of the subsurface transport and natural attenuation of petroleum hydrocarbon contaminants at the Bemidji, Minnesota crude-oil spill research site, we used aqueous tracers to investigate solute transport from the soil surface through the crude oil-contaminated unsaturated zone to the water table. We applied tracer solution to the soil surface within a 5 by 12 meter tracer test plot that ran from a heavily oil-contaminated area to an oil-free zone. The depth to the water table was about 6 meters. The tracer test plot was instrumented with soil moisture probes, tensiometers, suction lysimeters, and drive-point sampling wells. Sixty liters of solution containing about 6.0E03 mg/l rhodamine WT and 1.0E04 mg/l bromide was uniformly sprayed on the soil surface in October 2001. We monitored subsequent tracer movement in response to precipitation by obtaining water samples weekly using the suction lysimeters in the unsaturated zone and the drive point wells in the satura...
Ground-water recharge is an important factor affecting the Bemidji, Minnesota crude-oil spill sit... more Ground-water recharge is an important factor affecting the Bemidji, Minnesota crude-oil spill site. About 400,000 liters of crude oil remained in the ground after remediation was completed following the 1979 pipeline break. An automated data logging system was used to measure unsaturated zone properties relevant to estimating recharge and to evaluate their effects on dissolution of the oil. Laboratory and field testing of several soil-moisture probes indicated that the CS615 probe was better suited to estimating recharge in the glacial outwash at the Bemidji crude-oil spill site than the CS605 probes. Both probes are manufactured by Campbell Scientific Inc. The CS615 probe provided dependable and accurate data over long time periods, using a limited power supply, under the extreme weather conditions typical of northern Minnesota. Based on results of the testing, arrays of the CS615 probes, zero-maintenance tensiometers, and thermocouples were installed in the unsaturated zone at the...
An automated data logging system was used to measure unsaturated zone properties relevant to eval... more An automated data logging system was used to measure unsaturated zone properties relevant to evaluating the effects of recharge on dissolution of crude oil at a research site near Bemidji, Minnesota. Laboratory and field testing of several soil-moisture probes indicated that a CS615 "reflectometer" probe was better suited to estimating recharge in the glacial outwash at the site than was a CS605 time-domain reflectometry (TDR) probe. All probes were manufactured by Campbell Scientific Inc. The reflectometer probes provided dependable and accurate data over long time periods, were somewhat easier to install, and had less noise than the TDR probes. The reflectometer probe was better suited to the field conditions of having a limited power supply and the extreme weather typical of northern Minnesota. Probe type did not have a significant affect on estimates of recharge, with values from all of the probes ranging from 14.5 to 29.9 cm/yr. We also compared the response of TDR pr...
A large-scale aquifer test was carried out at a crude oil spill site near Bemidji, Minnesota. The... more A large-scale aquifer test was carried out at a crude oil spill site near Bemidji, Minnesota. The spill occurred in 1979 when a pipeline ruptured, spreading oil over a large area and creating three subsurface "pools" of high oil saturation near the water table. USGS scientists, in cooperation with researchers from several universities, have investigated the fate and transport of separate phase oil and hydrocarbons dissolved in ground water at this site since 1983. The primary goal of the aquifer test was to estimate parameters used in modeling processes such as subsurface flow of oil and water as well as natural attenuation of dissolved hydrocarbons in the plume. A secondary goal was to evaluate the effects of the oil on the parameters. Our aquifer test was carried out in July 2005 beneath the "north" oil pool, which occupies a 20x100 meter footprint. Prior to the test, the water table was about 6 meters below land surface, and the oil thickness in wells at the c...
In 1979 a crude-oil pipeline ruptured near Bemidji, Minnesota spilling about 1.7 million liters o... more In 1979 a crude-oil pipeline ruptured near Bemidji, Minnesota spilling about 1.7 million liters of crude oil onto a glacial-outwash deposit. Initial remediation efforts in 1979-80 removed about 75% of this oil. In 1983 the U.S. Geological Survey and several academic institutions began research to study the fate and transport of the petroleum hydrocarbons in the unsaturated and saturated zones at the site. In 1998 the Minnesota Pollution Control Agency (MPCA) requested that the pipeline company remove as much of the remaining oil as possible. A dual-pump recovery system was installed using five wells to remove the free-phase oil. Each well had an oil skimming pump as well as a deeper pump in the groundwater, which was used to create a cone of depression in the water table near the well. The oil/water mixture from the skimming pump was pumped to a treatment facility where the oil was separated for later removal from the site. Pumped wastewater was injected into an upgradient infiltrat...
Groundwater/surface-water (GW/SW) exchange and hyporheic processes are topics receiving increasin... more Groundwater/surface-water (GW/SW) exchange and hyporheic processes are topics receiving increasing attention from the hydrologic community. Hydraulic, chemical, temperature, geophysical, and remote sensing methods are used to achieve various goals (e.g., inference of GW/SW exchange, mapping of bed materials, etc.), but the application of these methods is constrained by site conditions such as water depth, specific conductance, bed material, and other factors. Researchers and environmental professionals working on GW/SW problems come from diverse fields and rarely have expertise in all available field methods; hence there is a need for guidance to design field campaigns and select methods that both contribute to study goals and are likely to work under site-specific conditions. Here, we present the spreadsheet-based GW/SW-Method Selection Tool (GW/SW-MST) to help practitioners identify methods for use in GW/SW and hyporheic studies. The GW/SW-MST is a Microsoft Excel-based decision support tool in which the user selects answers to questions about GW/SW-related study goals and site parameters and characteristics. Based on user input, the tool indicates which methods from a toolbox of 32 methods could potentially contribute to achieving the specified goals at the site described. This article is protected by copyright. All rights reserved.
A tracer test was conducted to aid in the investigation of water movement and solute transport at... more A tracer test was conducted to aid in the investigation of water movement and solute transport at a crude-oil spill site near Bemidji, Minnesota. Time of travel was measured using breakthrough curves for rhodamine WT and bromide tracers moving from the soil surface through oil-contaminated and oil-free unsaturated zones to the saturated zone. Results indicate that the rates of tracer movement were similar in the oil-free unsaturated and saturated zones compared to the oily zones. These results are somewhat surprising given the oil contamination in the unsaturated and saturated zones. Rhodamine tracer breakthrough in the unsaturated and saturated zones in general was delayed in comparison to bromide tracer breakthrough. Peak tracer concentrations for the lysimeters and wells in the oily zone were much greater than at the corresponding depths in the oil-free zone. Water and tracer movement in the oily zone was complicated by soil hydrophobicity and decreased oil saturations toward the...
As a part of a study of the subsurface transport and natural attenuation of petroleum hydrocarbon... more As a part of a study of the subsurface transport and natural attenuation of petroleum hydrocarbon contaminants at the Bemidji, Minnesota crude-oil spill research site, we used aqueous tracers to investigate solute transport from the soil surface through the crude oil-contaminated unsaturated zone to the water table. We applied tracer solution to the soil surface within a 5 by 12 meter tracer test plot that ran from a heavily oil-contaminated area to an oil-free zone. The depth to the water table was about 6 meters. The tracer test plot was instrumented with soil moisture probes, tensiometers, suction lysimeters, and drive-point sampling wells. Sixty liters of solution containing about 6.0E03 mg/l rhodamine WT and 1.0E04 mg/l bromide was uniformly sprayed on the soil surface in October 2001. We monitored subsequent tracer movement in response to precipitation by obtaining water samples weekly using the suction lysimeters in the unsaturated zone and the drive point wells in the satura...
Ground-water recharge is an important factor affecting the Bemidji, Minnesota crude-oil spill sit... more Ground-water recharge is an important factor affecting the Bemidji, Minnesota crude-oil spill site. About 400,000 liters of crude oil remained in the ground after remediation was completed following the 1979 pipeline break. An automated data logging system was used to measure unsaturated zone properties relevant to estimating recharge and to evaluate their effects on dissolution of the oil. Laboratory and field testing of several soil-moisture probes indicated that the CS615 probe was better suited to estimating recharge in the glacial outwash at the Bemidji crude-oil spill site than the CS605 probes. Both probes are manufactured by Campbell Scientific Inc. The CS615 probe provided dependable and accurate data over long time periods, using a limited power supply, under the extreme weather conditions typical of northern Minnesota. Based on results of the testing, arrays of the CS615 probes, zero-maintenance tensiometers, and thermocouples were installed in the unsaturated zone at the...
An automated data logging system was used to measure unsaturated zone properties relevant to eval... more An automated data logging system was used to measure unsaturated zone properties relevant to evaluating the effects of recharge on dissolution of crude oil at a research site near Bemidji, Minnesota. Laboratory and field testing of several soil-moisture probes indicated that a CS615 "reflectometer" probe was better suited to estimating recharge in the glacial outwash at the site than was a CS605 time-domain reflectometry (TDR) probe. All probes were manufactured by Campbell Scientific Inc. The reflectometer probes provided dependable and accurate data over long time periods, were somewhat easier to install, and had less noise than the TDR probes. The reflectometer probe was better suited to the field conditions of having a limited power supply and the extreme weather typical of northern Minnesota. Probe type did not have a significant affect on estimates of recharge, with values from all of the probes ranging from 14.5 to 29.9 cm/yr. We also compared the response of TDR pr...
A large-scale aquifer test was carried out at a crude oil spill site near Bemidji, Minnesota. The... more A large-scale aquifer test was carried out at a crude oil spill site near Bemidji, Minnesota. The spill occurred in 1979 when a pipeline ruptured, spreading oil over a large area and creating three subsurface "pools" of high oil saturation near the water table. USGS scientists, in cooperation with researchers from several universities, have investigated the fate and transport of separate phase oil and hydrocarbons dissolved in ground water at this site since 1983. The primary goal of the aquifer test was to estimate parameters used in modeling processes such as subsurface flow of oil and water as well as natural attenuation of dissolved hydrocarbons in the plume. A secondary goal was to evaluate the effects of the oil on the parameters. Our aquifer test was carried out in July 2005 beneath the "north" oil pool, which occupies a 20x100 meter footprint. Prior to the test, the water table was about 6 meters below land surface, and the oil thickness in wells at the c...
In 1979 a crude-oil pipeline ruptured near Bemidji, Minnesota spilling about 1.7 million liters o... more In 1979 a crude-oil pipeline ruptured near Bemidji, Minnesota spilling about 1.7 million liters of crude oil onto a glacial-outwash deposit. Initial remediation efforts in 1979-80 removed about 75% of this oil. In 1983 the U.S. Geological Survey and several academic institutions began research to study the fate and transport of the petroleum hydrocarbons in the unsaturated and saturated zones at the site. In 1998 the Minnesota Pollution Control Agency (MPCA) requested that the pipeline company remove as much of the remaining oil as possible. A dual-pump recovery system was installed using five wells to remove the free-phase oil. Each well had an oil skimming pump as well as a deeper pump in the groundwater, which was used to create a cone of depression in the water table near the well. The oil/water mixture from the skimming pump was pumped to a treatment facility where the oil was separated for later removal from the site. Pumped wastewater was injected into an upgradient infiltrat...
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