Occurrence and sources of radium in groundwater associated with oil fields in the southern San Joaquin Valley, California

American Chemical Society (ACS) | August 7th, 2019

Geochemical data from 40 water wells were used to examine the occurrence and sources of radium (Ra) in groundwater associated with three oil fields in California (Fruitva

Geochemical data from 40 water wells were used to examine the occurrence and sources of radium (Ra) in groundwater associated with three oil fields in California (Fruitvale, Lost Hills, South Belridge). 226Ra+228Ra activities (range = 0.010–0.51 Bq/L) exceeded the 0.185 Bq/L drinking-water standard in 18% of the wells (not drinking-water wells). Radium activities were correlated with TDS concentrations (p < 0.001, ρ = 0.90, range = 145–15,900 mg/L), Mn + Fe concentrations (p < 0.001, ρ = 0.82, range = <0.005–18.5 mg/L), and pH (p < 0.001, ρ = −0.67, range = 6.2–9.2), indicating Ra in groundwater was influenced by salinity, redox, and pH. Ra-rich groundwater was mixed with up to 45% oil-field water at some locations, primarily infiltrating through unlined disposal ponds, based on Cl, Li, noble-gas, and other data. Yet 228Ra/226Ra ratios in pond-impacted groundwater (median = 3.1) differed from those in oil-field water (median = 0.51). PHREEQC mixing calculations and spatial geochemical variations suggest that the Ra in the oil-field water was removed by coprecipitation with secondary barite and adsorption on Mn–Fe precipitates in the near-pond environment. The saline, organic-rich oil-field water subsequently mobilized Ra from downgradient aquifer sediments via Ra-desorption and Mn/Fe-reduction processes. This study demonstrates that infiltration of oil-field water may leach Ra into groundwater by changing salinity and redox conditions in the subsurface rather than by mixing with a high-Ra source.

Occurrence of natural and anthropogenic hexavalent chromium (Cr VI) in groundwater near a mapped plume, Hinkley, CA

U.S. Geological Survey (USGS) | March 22nd, 2018

This report describes (1) work done between January 2015 and May 2017 as part of the U.S. Geological Survey (USGS) hexavalent chromium, Cr(VI), background study and (2) t

This report describes (1) work done between January 2015 and May 2017 as part of the U.S. Geological Survey (USGS) hexavalent chromium, Cr(VI), background study and (2) the summative-scale approach to be used to estimate the extent of anthropogenic (man-made) Cr(VI) and background Cr(VI) concentrations near the Pacific Gas and Electric Company (PG&E) natural gas compressor station in Hinkley, California. Most of the field work for the study was completed by May 2017. The summative-scale approach and calculation of Cr(VI) background were not well-defined at the time the USGS proposal for the background Cr(VI) study was prepared but have since been refined as a result of data collected as part of this study. The proposed summative scale consists of multiple items, formulated as questions to be answered at each sampled well. Questions that compose the summative scale were developed to address geologic, hydrologic, and geochemical constraints on Cr(VI) within the study area. Each question requires a binary (yes or no) answer. A score of 1 will be assigned for an answer that represents data consistent with anthropogenic Cr(VI); a score of –1 will be assigned for an answer that represents data inconsistent with anthropogenic Cr(VI). The areal extent of anthropogenic Cr(VI) estimated from the summative-scale analyses will be compared with the areal extent of anthropogenic Cr(VI) estimated on the basis of numerical groundwater flow model results, along with particle-tracking analyses. On the basis of these combined results, background Cr(VI) values will be estimated for “Mojave-type” deposits, and other deposits, in different parts of the study area outside the summative-scale mapped extent of anthropogenic Cr(VI). 

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

Journal of Hydrology: Regional Studies (Elsevier) | April 11th, 2022

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

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), NH3, DOC, enriched δ13C-DIC, δ2H- CH4, δ13C-CH4, and δ13C-C2H6 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 4He 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.

Oil, Food, and Water: Challenges and Opportunities for California Agriculture

Pacific Institute | December 1st, 2015

A new comprehensive study by the Pacific Institute  sheds light on the risks posed when oil and gas exploration and production operate alongside agriculture. “There

A new comprehensive study by the Pacific Institute  sheds light on the risks posed when oil and gas exploration and production operate alongside agriculture. “There is growing concern about competition for land and water, and the impacts of soil and water contamination on the food supply and health and safety of farmworkers and consumers,” said Matthew Heberger, the study’s lead author. The disposal of oil and gas wastewater, which contains harmful chemicals, is a particular concern for agriculture. Disposal in unlined percolation pits poses a significant risk of contaminating groundwater resources that may, in turn, be used by agriculture. While this practice has been banned in several states, it is still widely used in California’s Central Valley, one of the nation’s most important agricultural regions. There are also serious deficiencies in the way California regulates the underground injection of wastes – current practices are not sufficiently protective of freshwater aquifers that may be used as drinking water or to irrigate crops and water livestock.

Organic geochemistry and toxicology of a stream impacted by unconventional oil and gas wastewater disposal operations

Applied Geochemistry (Elsevier) | March 10th, 2017

The large volume of wastewater produced during unconventional oil and gas (UOG) extraction is a significant challenge for the energy industry and of environmental concern

The large volume of wastewater produced during unconventional oil and gas (UOG) extraction is a significant challenge for the energy industry and of environmental concern, as the risks due to leaks, spills, and migration of these fluids into natural waters are unknown. UOG wastewater is often hypersaline, and contains myriad organic and inorganic substances added for production purposes and derived from the source rock or formation water. In this study, we examined the organic composition and toxicology of water and sediments in a stream adjacent to an underground injection disposal facility that handles UOG wastewaters.

Origin of methane and sources of high concentrations in Los Angeles groundwater

American Geophysical Union (AGU) | February 12th, 2018

High dissolved methane gas concentrations were measured in 37 groundwater samples collected in the Los Angeles Basin, California. The origin of the methane was identified

High dissolved methane gas concentrations were measured in 37 groundwater samples collected in the Los Angeles Basin, California. The origin of the methane was identified as microbial activity rather than from the burial and heating of organic material. The source of the methane was microbial production in shallow, oxygen-depleted aquifers rather than the upward migration or leakage of methane associated with oil fields in the basin.

Passage and Flow Considered Anew: Wild Salmon Restoration Via Hyrdo Relicensing

University of Montana | May 24th, 2016

Patterns and magnitude of flow alteration in California, USA

Freshwater Biology (Wiley) | December 27th, 2017

The importance of the natural flow regime to stream and river health has received growing attention over the last two decades. Quantifying natural river flows has become

The importance of the natural flow regime to stream and river health has received growing attention over the last two decades. Quantifying natural river flows has become an essential component of water resource planning, including assessments of water supplies (Vicuna,Maurer, Joyce, Dracup, & Purkey, 2007; Wurbs, 2005), reservoir operations (Hejazi, Cai, & Ruddell, 2008) and drought risk (Meko,Therrell, Baisan, & Hughes, 2001). Understanding the natural flow regime is also crucial for managing stream ecosystems.

Paying it Forward: The Path Toward Climate-Safe Infrastructure in California

Climate-Safe Infrastructure Working Group | September 1st, 2018

Potential Impacts of Future Geological Storage of CO2 on the Groundwater Resources in California’s Central Valley: Southern San Joaquin Basin Oil and Gas Production Analog for Geologic Carbon Storage

California Energy Commission (CEC) | May 1st, 2013

This study investigated the potential impacts of the injection and storage of large quantities of carbon dioxide on shallow water resources in California’s southern San

This study investigated the potential impacts of the injection and storage of large quantities of carbon dioxide on shallow water resources in California’s southern San Joaquin Basin, including the possibility that if such injection was properly planned it might help mitigate the land subsidence impacts related to over-pumping of groundwater. The project used simulation studies to investigate whether the basin-scale pressure changes and brine displacement caused by future carbon dioxide storage in the deep sediments could impact the groundwater-surface water systems in the area. Two simulation models were developed. The Deep Basin Reservoir Simulation Model was developed for accurately simulating the multiphase processes of carbon dioxide and brine flow occurring in deep sequestration reservoirs. The Shallow Water Resources Impact Simulation Model was developed for accurately predicting the impact of deep carbon dioxide sequestration on a stressed water system, including evaluation of carbon dioxide-related impacts in the context of the long-term groundwater and subsidence trends occurring in the area as a result of other water stresses such as pumping and irrigation. The Deep Basin Reservoir Simulation Model showed that the caprock and overlying geological units had sufficient barrier attributes to prevent pressure propagation from the injection layer to the shallow aquifers. The Shallow Water Resources Impact Simulation Model simulation results showed that deep carbon dioxide injection would create only minor head change and surface uplift in the shallow model layers. Overall the simulation results suggested that even large carbon dioxide storage projects should have minimal impact on shallow groundwater and surface water systems if thick layers of shales and sands separated the deep CO2 injection layers from shallow aquifers. Researchers believed this study justified devoting resources to evaluating the potential impact from localized pathways or from induced seismicity to more thoroughly investigate the feasibility of carbon dioxide storage in the southern San Joaquin Basin.