Peter B McMahon
Peter is a Research Hydrologist with the USGS Colorado Water Science Center in Lakewood, CO.
Pete McMahon’s current research interests include understanding the effects of hydrocarbon production activities on groundwater quality and identifying natural and human processes that create regional- and national-scale patterns in the chemistry of groundwater. He uses geochemical, isotope, noble-gas, and groundwater-age tracers to understand the origin and fate of chemicals of concern in groundwater.
Education and Certifications
Ph.D., 1990, Geology, University of South Carolina at Columbia
M.A., 1984, Geology, University of Texas at Austin
B.S., 1981, Geology, University of Missouri at Columbia
Science and Products
Filter Total Items: 14
Methane and benzene in drinking-water wells overlying the Eagle Ford, Fayetteville, and Haynesville Shale hydrocarbon production areas
Groundwater samples were collected from domestic and public-supply wells in the Eagle Ford study area in 201516, in the Fayetteville study area in 2015, and in the Haynesville study area in 201415. One sample of produced water was collected from a gas well in the Haynesville Shale in Rusk County, Texas in 2010, and 5 samples of produced water were collected from oil and condensate wells in the Ea
Produced water chemistry for samples from four petroleum wells, southern San Joaquin Valley, California, 2014
The U.S. Geological Survey (USGS) in cooperation with the California State Water Resources Control Board collected produced water samples from four petroleum wells in the southern San Joaquin Valley on November 5, 2014. This digital dataset contains the site information, analyzing laboratories and methods, and water chemistry and quality control results for these samples. Water chemistry results i
Filter Total Items: 116
Noble gas signatures constrain oil-field water as the carrier phase of hydrocarbons occurring in shallow aquifers in the San Joaquin Basin, USA
Noble gases record fluid interactions in multiphase subsurface environments through fractionation processes during fluid equilibration. Water in the presence of hydrocarbons at the subsurface acquires a distinct elemental signature due to the difference in solubility between these two fluids. We find the atmospheric noble gas signature in produced water is partially preserved after hydrocarbons pr
Authors
Ruta Karolyte, Peter H. Barry, Andrew G. Hunt, Justin T. Kulongoski, R. L. Tyne, Tracy Davis, Michael Wright, Peter B. McMahon, C. J. Ballentine
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;
Authors
Peter B. McMahon, Matthew K. Landon, Tracy Davis, Michael Wright, Celia Z. Rosecrans, Robert Anders, Michael Land, Justin T. Kulongoski, Andrew G. Hunt
Geochemistry and age of groundwater in the Williston Basin, USA: Assessing potential effects of shale-oil production on groundwater quality
Thirty water wells were sampled in 2018 to understand the geochemistry and age of groundwater in the Williston Basin and assess potential effects of shale-oil production from the Three Forks-Bakken petroleum system (TBPS) on groundwater quality. Two geochemical groups are identified using hierarchical cluster analysis. Group 1 represents the younger (median 4He = 21.49 × 10−8 cm3 STP/g), less chem
Authors
Peter B. McMahon, Joel M. Galloway, Andrew G. Hunt, Kenneth Belitz, Bryant Jurgens, Tyler D. Johnson
Origin and geochemistry of formation waters from the lower Eagle Ford Group, Gulf Coast Basin, south central Texas
The lower Eagle Ford Group (LEFG) is one of the most productive continuous hydrocarbon plays in the United States but few associated produced waters data and minimal interpretation have been published. This effort focuses on results from compositional and isotopic data from 39 produced water samples collected from horizontal wells producing from the LEFG in south central Texas. The depth of the LE
Authors
Mark A Engle, Colin A. Doolan, Janet K. Pitman, Matthew S. Varonka, Jessica Chenault, William H. Orem, Peter B. McMahon, Aaron M. Jubb
Fluoride occurrence in United States groundwater
Data from 38,105 wells were used to characterize fluoride (F) occurrence in untreated United States (U.S.) groundwater. For domestic wells (n = 11,032), water from which is generally not purposely fluoridated or monitored for quality, 10.9% of the samples have F concentrations >0.7 mg/L (U.S. Public Health Service recommended optimal F concentration in drinking water for preventing tooth decay) (8
Authors
Peter B. McMahon, Craig J. Brown, Tyler D. Johnson, Kenneth Belitz, Bruce D. Lindsey
Multiple-well monitoring site adjacent to the Lost Hills oil field, Kern County, California
The U.S. Geological Survey (USGS), in cooperation with the California State Water Resources Control Board, is evaluating several questions about oil and gas development and groundwater resources in California, including (1) the location of groundwater resources; (2) the proximity of oil and gas operations and groundwater and the geologic materials between them; (3) the location of evidence (or no
Authors
Rhett R. Everett, Adam Kjos, Anthony A. Brown, Janice M. Gillespie, Peter B. McMahon
Occurrence and sources of radium in groundwater associated with oil fields in the southern San Joaquin Valley, California
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 concentrati
Authors
Peter B. McMahon, Avner Vengosh, Tracy Davis, Matthew K. Landon, Rebecca L. Tyne, Michael Wright, Justin T. Kulongoski, Andrew G. Hunt, Peter H. Barry, A.J. Kondash, Z. Wang, Christopher J. Ballentine
Groundwater quality and hydrology with emphasis on selenium mobilization and transport in the Lower Gunnison River Basin, Colorado, 2012–16
Dissolved selenium is a contaminant of concern in the lower Gunnison River Basin, Colorado. Selenium is naturally present in the Cretaceous Mancos Shale and is leached to groundwater and surface water by irrigation. The groundwater on the east side of the Uncompahgre River in Delta and Montrose Counties is one of the primary sources of selenium concentration and load to surface water in the lower
Authors
Judith C. Thomas, Peter B. McMahon, L. R. Arnold
Hydrocarbons in upland groundwater, Marcellus Shale Region, Northeastern Pennsylvania and Southern New York, USA
Water samples from 50 domestic wells located <1 km (proximal) and >1 km (distal) from shale-gas wells in upland areas of the Marcellus Shale region were analyzed for chemical, isotopic, and groundwater-age tracers. Uplands were targeted because natural mixing with brine and hydrocarbons from deep formations is less common in those areas compared to valleys. CH4-isotope, predrill CH4-concentration,
Authors
Peter B. McMahon, Bruce D. Lindsey, Matthew D. Conlon, Andrew G. Hunt, Kenneth Belitz, Bryant Jurgens, Brian A. Varela
By
Water Resources Mission Area, Energy Resources Program, National Water Quality Program, California Water Science Center, Central Energy Resources Science Center, Colorado Water Science Center, Geology, Geophysics, and Geochemistry Science Center, Geology, Minerals, Energy, and Geophysics Science Center, New England Water Science Center, Pennsylvania Water Science Center
Groundwater quality of a public supply aquifer in proximity to oil development, Fruitvale Oil Field, Bakersfield, California
Due to concerns over the effects of oil production activities on groundwater quality in California, chemical, isotopic, dissolved gas and age-dating tracers were analyzed in samples collected from public-supply wells and produced-water sites in the Fruitvale oil field (FVOF). A combination of newly collected and historical data was used to determine whether oil formation fluids have mixed with gro
Authors
Michael Wright, Peter B. McMahon, Matthew K. Landon, Justin T. Kulongoski
Methane emissions from groundwater pumping in the USA
Atmospheric methane accumulation contributes to climate change, hence quantifying methane emissions is essential to assess and model the impacts. Here we estimate methane emissions from groundwater pumping in the Los Angeles Basin (LAB), north-eastern Pennsylvania, and the Principal aquifers of the USA using the average concentrations of methane in groundwater and annual groundwater pumping volume
Authors
Justin T. Kulongoski, Peter B. McMahon
Elevated manganese concentrations in United States groundwater, role of land surface–soil–aquifer connections
Chemical data from 43 334 wells were used to examine the role of land surface–soil–aquifer connections in producing elevated manganese concentrations (>300 μg/L) in United States (U.S.) groundwater. Elevated concentrations of manganese and dissolved organic carbon (DOC) in groundwater are associated with shallow, anoxic water tables and soils enriched in organic carbon, suggesting soil-derived DOC
Authors
Peter B. McMahon, Kenneth Belitz, James E. Reddy, Tyler D. Johnson
Science and Products
Filter Total Items: 14
Methane and benzene in drinking-water wells overlying the Eagle Ford, Fayetteville, and Haynesville Shale hydrocarbon production areas
Groundwater samples were collected from domestic and public-supply wells in the Eagle Ford study area in 201516, in the Fayetteville study area in 2015, and in the Haynesville study area in 201415. One sample of produced water was collected from a gas well in the Haynesville Shale in Rusk County, Texas in 2010, and 5 samples of produced water were collected from oil and condensate wells in the Ea
Produced water chemistry for samples from four petroleum wells, southern San Joaquin Valley, California, 2014
The U.S. Geological Survey (USGS) in cooperation with the California State Water Resources Control Board collected produced water samples from four petroleum wells in the southern San Joaquin Valley on November 5, 2014. This digital dataset contains the site information, analyzing laboratories and methods, and water chemistry and quality control results for these samples. Water chemistry results i
Filter Total Items: 116
Noble gas signatures constrain oil-field water as the carrier phase of hydrocarbons occurring in shallow aquifers in the San Joaquin Basin, USA
Noble gases record fluid interactions in multiphase subsurface environments through fractionation processes during fluid equilibration. Water in the presence of hydrocarbons at the subsurface acquires a distinct elemental signature due to the difference in solubility between these two fluids. We find the atmospheric noble gas signature in produced water is partially preserved after hydrocarbons pr
Authors
Ruta Karolyte, Peter H. Barry, Andrew G. Hunt, Justin T. Kulongoski, R. L. Tyne, Tracy Davis, Michael Wright, Peter B. McMahon, C. J. Ballentine
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;
Authors
Peter B. McMahon, Matthew K. Landon, Tracy Davis, Michael Wright, Celia Z. Rosecrans, Robert Anders, Michael Land, Justin T. Kulongoski, Andrew G. Hunt
Geochemistry and age of groundwater in the Williston Basin, USA: Assessing potential effects of shale-oil production on groundwater quality
Thirty water wells were sampled in 2018 to understand the geochemistry and age of groundwater in the Williston Basin and assess potential effects of shale-oil production from the Three Forks-Bakken petroleum system (TBPS) on groundwater quality. Two geochemical groups are identified using hierarchical cluster analysis. Group 1 represents the younger (median 4He = 21.49 × 10−8 cm3 STP/g), less chem
Authors
Peter B. McMahon, Joel M. Galloway, Andrew G. Hunt, Kenneth Belitz, Bryant Jurgens, Tyler D. Johnson
Origin and geochemistry of formation waters from the lower Eagle Ford Group, Gulf Coast Basin, south central Texas
The lower Eagle Ford Group (LEFG) is one of the most productive continuous hydrocarbon plays in the United States but few associated produced waters data and minimal interpretation have been published. This effort focuses on results from compositional and isotopic data from 39 produced water samples collected from horizontal wells producing from the LEFG in south central Texas. The depth of the LE
Authors
Mark A Engle, Colin A. Doolan, Janet K. Pitman, Matthew S. Varonka, Jessica Chenault, William H. Orem, Peter B. McMahon, Aaron M. Jubb
Fluoride occurrence in United States groundwater
Data from 38,105 wells were used to characterize fluoride (F) occurrence in untreated United States (U.S.) groundwater. For domestic wells (n = 11,032), water from which is generally not purposely fluoridated or monitored for quality, 10.9% of the samples have F concentrations >0.7 mg/L (U.S. Public Health Service recommended optimal F concentration in drinking water for preventing tooth decay) (8
Authors
Peter B. McMahon, Craig J. Brown, Tyler D. Johnson, Kenneth Belitz, Bruce D. Lindsey
Multiple-well monitoring site adjacent to the Lost Hills oil field, Kern County, California
The U.S. Geological Survey (USGS), in cooperation with the California State Water Resources Control Board, is evaluating several questions about oil and gas development and groundwater resources in California, including (1) the location of groundwater resources; (2) the proximity of oil and gas operations and groundwater and the geologic materials between them; (3) the location of evidence (or no
Authors
Rhett R. Everett, Adam Kjos, Anthony A. Brown, Janice M. Gillespie, Peter B. McMahon
Occurrence and sources of radium in groundwater associated with oil fields in the southern San Joaquin Valley, California
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 concentrati
Authors
Peter B. McMahon, Avner Vengosh, Tracy Davis, Matthew K. Landon, Rebecca L. Tyne, Michael Wright, Justin T. Kulongoski, Andrew G. Hunt, Peter H. Barry, A.J. Kondash, Z. Wang, Christopher J. Ballentine
Groundwater quality and hydrology with emphasis on selenium mobilization and transport in the Lower Gunnison River Basin, Colorado, 2012–16
Dissolved selenium is a contaminant of concern in the lower Gunnison River Basin, Colorado. Selenium is naturally present in the Cretaceous Mancos Shale and is leached to groundwater and surface water by irrigation. The groundwater on the east side of the Uncompahgre River in Delta and Montrose Counties is one of the primary sources of selenium concentration and load to surface water in the lower
Authors
Judith C. Thomas, Peter B. McMahon, L. R. Arnold
Hydrocarbons in upland groundwater, Marcellus Shale Region, Northeastern Pennsylvania and Southern New York, USA
Water samples from 50 domestic wells located <1 km (proximal) and >1 km (distal) from shale-gas wells in upland areas of the Marcellus Shale region were analyzed for chemical, isotopic, and groundwater-age tracers. Uplands were targeted because natural mixing with brine and hydrocarbons from deep formations is less common in those areas compared to valleys. CH4-isotope, predrill CH4-concentration,
Authors
Peter B. McMahon, Bruce D. Lindsey, Matthew D. Conlon, Andrew G. Hunt, Kenneth Belitz, Bryant Jurgens, Brian A. Varela
By
Water Resources Mission Area, Energy Resources Program, National Water Quality Program, California Water Science Center, Central Energy Resources Science Center, Colorado Water Science Center, Geology, Geophysics, and Geochemistry Science Center, Geology, Minerals, Energy, and Geophysics Science Center, New England Water Science Center, Pennsylvania Water Science Center
Groundwater quality of a public supply aquifer in proximity to oil development, Fruitvale Oil Field, Bakersfield, California
Due to concerns over the effects of oil production activities on groundwater quality in California, chemical, isotopic, dissolved gas and age-dating tracers were analyzed in samples collected from public-supply wells and produced-water sites in the Fruitvale oil field (FVOF). A combination of newly collected and historical data was used to determine whether oil formation fluids have mixed with gro
Authors
Michael Wright, Peter B. McMahon, Matthew K. Landon, Justin T. Kulongoski
Methane emissions from groundwater pumping in the USA
Atmospheric methane accumulation contributes to climate change, hence quantifying methane emissions is essential to assess and model the impacts. Here we estimate methane emissions from groundwater pumping in the Los Angeles Basin (LAB), north-eastern Pennsylvania, and the Principal aquifers of the USA using the average concentrations of methane in groundwater and annual groundwater pumping volume
Authors
Justin T. Kulongoski, Peter B. McMahon
Elevated manganese concentrations in United States groundwater, role of land surface–soil–aquifer connections
Chemical data from 43 334 wells were used to examine the role of land surface–soil–aquifer connections in producing elevated manganese concentrations (>300 μg/L) in United States (U.S.) groundwater. Elevated concentrations of manganese and dissolved organic carbon (DOC) in groundwater are associated with shallow, anoxic water tables and soils enriched in organic carbon, suggesting soil-derived DOC
Authors
Peter B. McMahon, Kenneth Belitz, James E. Reddy, Tyler D. Johnson