Geology topics

Robert Anders

Publications and source records attributed to Robert Anders.

11 recordsLinked to original sources

USGS2024

Groundwater quality near the Placerita Oil Field, California, 2018

Groundwater-quality data and potential fluid-migration pathways near the Placerita Oil Field in Los Angeles County, California, were examined by the U.S. Geological Survey to determine if oil-field fluids (water and gas from oil-producing and non-producing zones) have mixed with groundwater resources. Six of the 13 new groundwater samples collected for this study contained petroleum hydrocarbons, thermogenic gas, inorganic chemical signatures, and (or) isotopic values consistent with potential mixing with fluids from hydrocarbon-bearing formations. For historical groundwater samples, benzene was the most detected petroleum hydrocarbon. The historical groundwater samples with a benzene concentration greater than 0.5 micrograms per liter were from environmental monitoring wells at industrial or commercial facilities unrelated to oil and gas development that, in many cases, have identified soil or groundwater contamination and were not typically analyzed for other constituents that could provide additional lines of evidence for potential mixing with oil-field fluids. Methane was not detected in any of the 12 historical samples with a reported measurement. Reviewing historical data revealed factors that could potentially adversely affect groundwater quality in the study area. These factors include modified hydraulic gradients caused by large volumes of water extracted from the main production area and reinjected downgradient into nonproducing zones, well-barrier failures in wells constructed in the northern part of the oil field before the 1970s, well-barrier failures in produced-water disposal wells downgradient from the main production area, and naturally occurring hydrocarbons at shallow intervals. The groundwater samples most geochemically similar to samples from hydrocarbon-bearing formations were in areas where hydrocarbons are naturally occurring at shallow intervals and where oil development is at shallow depths. Additional data for hydraulic heads, water quality, and formation temperatures at multiple depths in areas with large injection volumes and well-integrity issues are needed to evaluate whether those factors have contributed to mixing between fluids from oil-producing or injection formations and groundwater resources.

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USGS2022

Occurrence of water and thermogenic gas from oil-bearing formations in groundwater near the Orcutt Oil Field, California, USA

Study region Santa Barbara County, California, USA. Study focus To analyze a wide array of newly collected chemical, isotopic, dissolved gas, and age dating tracers in conjunction with historical data from groundwater and oil wells to determine if water and/or thermogenic gas from oil-bearing formations have mixed with groundwater in the Orcutt Oil Field and surrounding area. New hydrological insights for the region Three of 15 groundwater samples had compositions indicating potential mixing with water and/or thermogenic gas from oil-bearing formations. Relevant indicators included salinity tracers (TDS, Cl, Br), NH 3, DOC, enriched δ 13 C-DIC, δ 2 H-CH 4 , δ 13 C-CH 4 , and δ 13 C-C 2 H 6 values, and trace amounts of C3-C5 gas. The potential sources/pathways for oil-bearing formation water and/or thermogenic gas in groundwater overlying and adjacent to the Orcutt Oil Field include: (1) upward movement from formations developed for oil production due to: (a) natural migration; or (b) anthropogenic activity such as injection and/or movement along wellbores; and (2) oil and gas shows in overlying non-producing oil-bearing formations. Groundwater age tracers, elevated 4 He concentrations, and isotopic compositions of noble gases indicated legacy produced water ponds were not a source. This phase of the study relied on samples and data from existing infrastructure. Additional data on potential end-member compositions from new and existing wells and assessments of potential vertical head gradients and pathways between oil and groundwater zones may yield additional insight.

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USGS2021

Relative risk of groundwater-quality degradation near California (USA) oil fields estimated from 3H, 14C, and 4He

Relative risks of groundwater-quality degradation near selected California oil fields are estimated by examining spatial and temporal patterns in chemical and isotopic data in the context of groundwater-age categories defined by tritium and carbon-14. In the Coastal basins, western San Joaquin Valley (SJV), and eastern SJV; 82, 76, and 0% of samples are premodern (pre-1953 recharge), respectively; and 3, 0, and 31% are modern (recharged during or after 1953), respectively. Carbon-14 and helium-4 data indicate most premodern samples are 1000 to 10,000 (33%) or >10,000 (50%) years old. Organic chemicals that could be associated with deeper hydrocarbon reservoirs (e.g. thermogenic gases and benzene) occur most frequently in premodern groundwater, suggesting premodern groundwater has a higher risk of degradation from upward migration of hydrocarbons than modern and mixed-age groundwater. Low sulfate concentrations in some premodern groundwater containing high thermogenic-methane concentrations (>28 mg/L) indicate methane attenuation associated with sulfate reduction can be limited in premodern groundwater. The more common occurrence of manufactured compounds, like tetrachloroethene, in modern and mixed-age groundwater than in premodern groundwater indicates modern and mixed-age groundwater has a higher risk of degradation from land-surface sources than premodern groundwater. Time-series data for chloride in groundwater affected by disposal of oil-field water in unlined ponds indicate some modern and mixed-age groundwater are susceptible to chemical migration within 2–3 km of surface sources. Timescales for diluting chloride concentrations in groundwater with fresh recharge once disposal ponds are decommissioned are shorter in mixed-age groundwater with large fractions of modern water (9–14 years in one example) than in mixed-age groundwater with large fractions of premodern water (no evidence of dilution after 12 years of monitoring in one example). The presence of predominantly premodern groundwater in the Coastal basins and western SJV indicates these areas have relatively high risk from upward migration of hydrocarbons, reduced methane attenuation capacity, and long dilution times, whereas predominantly modern- and mixed-age groundwater in the eastern SJV indicates this area has relatively high risk from chemical migration from land-surface sources and subsequent extensive spreading. Age-based characterizations of relative risk could inform the design of groundwater-monitoring programs near oil fields in terms of the spatial distribution of monitoring points relative to source areas and monitoring frequency and duration.

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USGS2018

Geologic, hydrologic, and water-quality data from multiple-well monitoring sites in the Bunker Hill and Yucaipa Groundwater Subbasins, San Bernardino County, California, 1974–2016

In 1974, the U.S. Geological Survey (USGS), in cooperation with the San Bernardino Valley Municipal Water District, initiated a study to assess the regional groundwater resources in the Bunker Hill Subbasin of the Upper Santa Ana Valley Groundwater Basin in San Bernardino County, California. The study area expanded east into the Yucaipa Subbasin in 1996. This report compiles the geologic (borehole lithology and geophysical logs) and hydrologic (water-quality and water-level) data collected from 1974–2016 for 11 multiple-well monitoring sites (48 individual wells) constructed by the USGS in the Bunker Hill (7 sites) and Yucaipa (4 sites) Groundwater Subbasins. Approximately 240 water-quality samples from the 11 sites were analyzed for constituents including major and minor ions, nutrients, selected trace elements, organic wastewater compounds (OWCs), volatile organic compounds (VOCs), pesticides and pesticide degradates, the stable isotopes of hydrogen, oxygen, and nitrogen, and the radiogenic isotopes of tritium and carbon-14. All environmental data associated with these sites are available on the project web page for the San Bernardino Optimal Basin Management study ( https://ca.water.usgs.gov/sanbern/ ) and the Yucaipa Valley Hydrogeology study ( https://ca.water.usgs.gov/yucaipa/ ). Quality-assurance blank samples were processed periodically throughout the study and show that approximately 2.4 percent of the analytical results for major and minor ions, trace elements, and nutrients, and 1.5 percent of the results for VOCs fall below the acceptable study reporting limits and therefore are censored.

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USGS2013

A geochemical approach to determine sources and movement of saline groundwater in a coastal aquifer

Geochemical evaluation of the sources and movement of saline groundwater in coastal aquifers can aid in the initial mapping of the subsurface when geological information is unavailable. Chloride concentrations of groundwater in a coastal aquifer near San Diego, California, range from about 57 to 39,400 mg/L. On the basis of relative proportions of major-ions, the chemical composition is classified as Na-Ca-Cl-SO 4 , Na-Cl, or Na-Ca-Cl type water. δ 2 H and δ 18 O values range from −47.7‰ to −12.8‰ and from −7.0‰ to −1.2‰, respectively. The isotopically depleted groundwater occurs in the deeper part of the coastal aquifer, and the isotopically enriched groundwater occurs in zones of sea water intrusion. 87 Sr/ 86 Sr ratios range from about 0.7050 to 0.7090, and differ between shallower and deeper flow paths in the coastal aquifer. 3 H and 14 C analyses indicate that most of the groundwater was recharged many thousands of years ago. The analysis of multiple chemical and isotopic tracers indicates that the sources and movement of saline groundwater in the San Diego coastal aquifer are dominated by: (1) recharge of local precipitation in relatively shallow parts of the flow system; (2) regional flow of recharge of higher-elevation precipitation along deep flow paths that freshen a previously saline aquifer; and (3) intrusion of sea water that entered the aquifer primarily during premodern times. Two northwest-to-southeast trending sections show the spatial distribution of the different geochemical groups and suggest the subsurface in the coastal aquifer can be separated into two predominant hydrostratigraphic layers.

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USGS2011

Water-quality data for the Russian River Basin, Mendocino and Sonoma Counties, California, 2005-2010

Since 2003, the U.S. Geological Survey, in cooperation with the Sonoma County Water Agency, has been collecting chemical, microbiological, and isotopic data from surface-water and groundwater sites in Mendocino and Sonoma Counties, California. The investigation is being conducted to determine water-quality baseline conditions for the Russian River during the summer months and to characterize the water-quality in the area of the Sonoma County Water Agency's water-supply facility where Russian River water is diverted and treated by riverbank filtration. This report is a compilation of the hydrologic and water-quality data collected from 14 Russian River sites, 8 tributary sites, 1 gravel-terrace pit site, 14 groundwater wells, and a wastewater treatment plant between the city of Ukiah and the town of Duncans Mills for the period August 2005 through October 2010. Field measurements included discharge, barometric pressure, dissolved oxygen, pH, specific conductance, temperature, and turbidity. All samples were analyzed for nutrients, major ions, trace metals, total and dissolved organic carbon, organic wastewater compounds, standard bacterial indicators, and the stable isotopes of hydrogen and oxygen. Standard bacterial indicators included total coliform, Escherichia coli, enterococci, and Clostridium perfringens for the period 2005 through 2007, and total and fecal coliform, and enterococci for 2010. In addition, enrichment of enterococci was performed on all surface-water samples collected during summer 2006, for detection of the human-associated enterococcal surface protein in Enterococcus faecium to assess the presence of sewage effluent in the Russian River. Other analyses included organic wastewater compounds of bed sediment samples collected from four Russian River sites during 2005; carbon-13 isotopic values of the dissolved inorganic carbon for surface-water and groundwater samples collected during 2006; human-use pharmaceuticals on Russian River samples collected during 2007 and 2010; and the radiogenic isotopes tritium and carbon-14 for groundwater samples collected during 2008.

Data Series↗

USGS2007

Use of carboxylated microspheres to assess transport potential of Cryptosporidium parvum oocysts at the Russian River water supply facility, Sonoma County, California

Carboxylated microspheres were employed as surrogates to assess the transport potential of Cryptosporidium parvum oocysts during forced- and natural-gradient tests conducted in July and October 2004. The tests involved poorly-sorted, near-surface sediments where groundwater is pumped from an alluvial aquifer underlying the Russian River, Sonoma County, CA. In an off channel infiltration basin and within the river, a mixture (2-, 3-, and 5- μm diameters) of fluorescently-labeled carboxylated microspheres and bromide tracers were used in two injection and recovery tests to assess sediment removal efficiency for the microspheres. Bottom sediments varied considerably in their filtration efficiency for Cryptosporidium .

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USGS2006

Water-Quality Data for the Lower Russian River Basin, Sonoma County, California, 2003-2004

In 2003, the U.S. Geological Survey, in cooperation with the Sonoma County Water Agency, began a study to determine the chemical, microbiological, and isotopic composition of the surface water and ground water in selected areas of the Lower Russian River Basin, Sonoma County, California. This report is a compilation of the hydrologic and water-quality data collected from 10 Russian River sites, 1 gravel-terrace pit site, 12 ground-water sites, 11 tributary sites including Mark West Creek, and 2 estuary sites between the city of Healdsburg and the Pacific Ocean, for the period August 2003 to September 2004. Field measurements made included streamflow, barometric pressure, dissolved oxygen, pH, specific conductance, and turbidity. Water samples were analyzed for nutrients, major ions, total and dissolved organic carbon, trace elements, mercury, wastewater compounds, total coliform, Escherichia coli, Enterococci, Clostridium perfringens, and the stable isotopes of hydrogen and oxygen. Discharge measurements and sampling techniques were modified to accommodate the very low summer flows at most of the tributaries, and discharge measurements were made with an acoustic Doppler velocity meter at the estuary river site to overcome the complexities associated with tidal influences.

Data Series↗

USGS2005

Virus fate and transport during artificial recharge with recycled water

A field‐scale experiment was conducted at a research site using bacterial viruses (bacteriophage) MS2 and PRD1 as surrogates for human viruses, bromide as a conservative tracer, and tertiary‐treated municipal wastewater (recycled water) to investigate the fate and transport of viruses during artificial recharge. Observed virus concentrations were fitted using a mathematical model that simulates virus transport in one‐dimensional, homogeneous, water‐saturated porous media accounting for virus sorption (or filtration), virus inactivation, and time‐dependent source concentration. The fitted time‐dependent clogging rate constants were used to estimate the collision efficiencies for bacteriophage MS2 and PRD1 during vertical fully saturated flow. Furthermore, the corresponding time‐dependent collision efficiencies for both bacteriophage asymptotically reached similar values at the various sampling locations. These results can be used to develop an optimal management scenario to maximize the amount of recycled water that can be applied to the spreading grounds while still maintaining favorable attachment conditions for virus removal.

Water Resources Research↗

USGS2004

Virus fate and transport during recharge using recycled water at a research field site in the Montebello Forebay, Los Angeles County, California, 1997-2000

Total and fecal coliform bacteria distributions in subsurface water samples collected at a research field site in Los Angeles County were found to increase from nondetectable levels immediately before artificial recharge using tertiary-treated municipal wastewater (recycled water). This rapid increase indicates that bacteria can move through the soil with the percolating recycled water over intervals of a few days and vertical and horizontal distances of about 3 meters. This conclusion formed the basis for three field-scale experiments using bacterial viruses (bacteriophage) MS2 and PRD1 as surrogates for human enteric viruses and bromide as a conservative tracer to determine the fate and transport of viruses in recycled water during subsurface transport under actual recharge conditions. The research field site consists of a test basin constructed adjacent to a large recharge facility (spreading grounds) located in the Montebello Forebay of Los Angeles County, California. The soil beneath the test basin is predominantly medium to coarse, moderately sorted, grayish-brown sand. The three tracer experiments were conducted during August 1997, August-September 1998, and August 2000. For each experiment, prepared solutions of bacteriophage and bromide were sprayed on the surface of the water in the test basin and injected, using peristaltic pumps, directly into the feed pipe delivering the recycled water to the test basin. Extensive data were obtained for water samples collected from the test basin itself and from depths of 0.3, 0.6, 1.0, 1.5, 3.0, and 7.6 meters below the bottom of the test basin. The rate of bacteriophage inactivation in the recycled water, independent of any processes occurring in the subsurface, was determined from measurements on water samples from the test basin. Regression analysis of the ratios of bacteriophage to bromide was used to determine the attenuation rates for MS2 and PRD1, defined as the logarithmic reduction in the ratio during each experiment. Although the inactivation rates increased during the third tracer experiment, they were nearly two orders of magnitude less than the attenuation rates. Therefore, adsorption, not inactivation, is the predominant removal mechanism for viruses during artificial recharge. Using the colloid-filtration model, the collision efficiency was determined for both bacteriophage during the second and third field-scale tracer experiments. The collision efficiency confirms that more favorable attachment conditions existed for PRD1, especially during the third tracer experiment. The different collision efficiencies between the second and third tracer experiments possibly were due to changing hydraulic conditions at the research field site during each experiment. The field data suggest that an optimal management scenario might exist to maximize the amount of recycled water that can be applied to the spreading grounds while still maintaining favorable attachment conditions for virus removal and thereby ensuring protection of the ground-water supply.

Scientific Investigations Report↗

USGS1995

Geohydrology, water quality, and nitrogen geochemistry in the saturated and unsaturated zones beneath various land uses, Riverside and San Bernardino counties, California, 1991-93

The U.S. Geological Survey, in cooperation with the Eastern Municipal Water District, the Metropolitan Water District of Southern California, and the Orange County Water District, has completed a detailed study of the Hemet groundwater basin. The quantity of ground water stored in the basin in August 1992 is estimated to be 327,000 acre-feet. Dissolved-solids concentration ranged from 380 to 700 mg/L (milligrams per liter), except in small areas where the concentration exceeded 1,000 mg/L. Nitrate concentrations exceeded the U.S. Environmental Protection Agency Maximum Contaminant Level (MCL) of 10 mg/L nitrate (as nitrogen) in the southeastern part of the basin, in the Domenigoni Valley area, and beneath a dairy in the Diamond Valley area. Seven sites representing selected land uses-- residential, turf grass irrigated with reclaimed water, citrus grove, irrigated farm, poultry farm, and dairy (two sites)--were selected for detailed study of nitrogen geochemistry in the unsaturated zone. For all land uses, nitrate was the dominant nitrogen species in the unsaturated zone. Although nitrate was seasonally present in the shallow unsaturated zone beneath the residential site, it was absent at moderate depths, suggesting negligible migration of nitrate from the surface at this time. Microbial denitrification probably is occurring in the shallow unsaturated zone. High nitrate concentrations in the deep unsaturated zone (greater than 100 ft) suggest either significantly higher nitrate loading at some time in the past, or lateral movement of nitrate at depth. Nitrate also is seasonally present in the shallow unsaturated zone beneath the reclaimed-water site, and (in contrast with the residential site), nitrate is perennially present in the deeper unsaturated zone. Microbial denitrification in the unsaturated zone and in the capillary fringe above the water table decreases the concentrations of nitrate in pore water to below the MCL before reaching the water table. Pore water in the unsaturated zone beneath the citrus grove site contains very high concentrations of nitrate. Even though there are zones of microbial denitrification, nitrate seems to be migrating downward to the water table. The presence of a shallow perched-water zone beneath the irrigated-farm site prevents the vertical movement of nitrate from the surface to the regional water table. Above the perched zone, nitrate concentrations in the unsaturated zone are variable, ranging from below the MCL to four times the MCL. Periodically, nitrate is flushed from the shallow unsaturated zone to the perched-water zone. The unsaturated zone pore-moisture quality could not be adequately addressed because of the very dry conditions in the unsaturated zone beneath the poultry-farm site. Surficial clay deposits prevent water from percolating downward. At the two dairy sites, nitrate loading in pore water at the surface was very high, as great as 7,000 mg/L. Microbial denitrification in the unsaturated zone causes such concentrations to decrease rapidly with depth. At a depth of 20 ft, nitrate concentration was less than 100 mg/L. In areas where the depth to water is less than 20 ft, nitrate loading to ground water can be very high, whereas in areas where depth to water is greater than 100 ft, most of the nitrate is microbially removed before reaching the water table.

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