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Simulation of groundwater flow to evaluate hydrogeologic controls on a PFAS plume, Coakley Landfill Superfund site, Rockingham County, New Hampshire

Per- and polyfluoroalkyl substances (PFAS), including perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS), have been detected at combined concentrations above 2,000 nanograms per liter (ng/L) at groundwater seep locations near the Coakley Landfill Superfund site, in North Hampton, New Hampshire. The landfill was active from 1972 to 1985. An impermeable cap was placed on the landfill in 1998. The adjacent area to the Coakley Landfill has many water supply wells, and transport of PFAS compounds to the wells is a concern. Fracture anisotropy in the underlying bedrock aquifer complicates the understanding of PFAS transport because groundwater preferentially travels along fractures that may not align with the prevailing groundwater flow direction. In 2018, the U.S. Environmental Protection Agency and the U.S. Geological Survey began an investigation of the groundwater flow from the Coakley Landfill site. This report describes the modification of a numerical groundwater-flow model for the local area around the Coakley Landfill and summarizes findings of the investigation. In addition, this report includes a brief description of PFOA and PFOS occurrence, a discussion of model construction, evaluation of model performance through calibration, and discussion of simulation results for two periods (before and after capping). Limitations are also discussed. Results show that simulated groundwater flow moves from the Coakley Landfill to the west and north. Advective transport modeling using particle tracking shows that groundwater from the landfill discharges primarily to streams to the west and north, and a small amount is transported to distal wells. Dilution of contaminants through advection and dispersion likely plays a role in whether PFAS compounds from the landfill will be detected above laboratory reporting levels at distal wells.

New Hampshire

Monitoring marine eruptions

Introduction Submarine volcanoes produce much of the same seismicity and eruptive activity as subaerial volcanoes and can pose hazards to society. Although they can be monitored with similar techniques and methods as described in other chapters of this volume, their submerged location brings unique challenges. This chapter addresses these challenges and provides recommendations for monitoring volcanoes fully or partly in marine environments to meet the capabilities described in other chapters of this volume. The United States and its territories host dozens of submarine volcanoes with most (around 60) in the Commonwealth of the Northern Mariana Islands. Approximately 20 of the Northern Mariana Islands submarine volcanoes are known to be hydrothermally active, and 10 have confirmed eruptions since the 1950s (for example, Baker and others, 2008; Tepp and others, 2019a). Nine of those volcanoes were considered by the National Volcanic Threat Assessment (Ewert and others, 2018) to have a combination of eruptive type and summit depth that poses a higher risk of hazardous eruptions, although only one was listed as a moderate (level 3) threat. Other notable submarine volcanoes of interest to the United States that have historically erupted are Axial Seamount off the Washington State coast, Kamaʻehuakanaloa in Hawaiʻi, and Vailuluʻu seamount in American Samoa. All of these, however, have a low risk of hazards because of their depth (greater than 600 meters below sea level) and eruptive type and so are not included in the National Volcanic Threat Assessment. In addition to submarine volcanoes, the submerged flanks of island volcanoes can also be a source of hazardous submarine eruptions—for example, the 1877 eruption of Mauna Loa, Hawai‘i, in Kealakekua Bay (Wanless and others, 2006). The most notable submarine eruption in recent times was the 2022 eruption of Hunga Tonga–Hunga Haʻapai in Tonga, which was one of the largest eruptions on Earth in the past 100 years. It created a massive volcanic plume, unprecedented shock waves, and far-reaching tsunami (Lynett and others, 2022). Other recent submarine eruptions in the Pacific Ocean Basin have produced subaerial plumes that reached aircraft heights (Carey and others, 2014) and large pumice rafts that can affect marine traffic and harbors (for example, Jutzeler and others, 2014; Kornei, 2019). These examples illustrate the potential hazards of major submarine eruptions. Yet, submarine volcanoes are largely unmonitored, and many eruptions occur that are unnoticed or only identified hours or days afterward. Within U.S. territory, submarine volcanoes in the Northern Mariana Islands have been known to produce eruptive activity that can affect society. Reports from fishermen and other marine vessels in the Northern Mariana Islands have noted underwater explosions, sea-surface discoloration, and bubbling water, all of which are known to be signs of submarine volcanic activity. South Sarigan seamount, located about 160 kilometers (km) north of Saipan, erupted in 2010 from greater than 150 meters below the sea surface, resulting in a gas and ash plume that reached more than 11.9 km into the atmosphere (for example, Searcy, 2013; Embley and others, 2014), high enough to affect international air traffic. Precursory and co-eruptive seismicity was detected on the regional Northern Mariana Islands seismic network (Searcy, 2013) and on global monitoring instruments (Green and others, 2013). Monitoring of submarine volcanoes is best accomplished with marine-based instrumentation, which is also useful for monitoring small island volcanoes that may not have the land area necessary for comprehensive subaerial monitoring. The primary marine-based instrumentation used for submarine volcanoes includes ocean-bottom pressure sensors to assess sea-floor deformation, ocean-bottom seismometers (OBSs) to detect seismicity, and both moored and ocean-bottom hydrophones to detect submarine explosions. Other sensors offer important monitoring data, such as turbidity, temperature, and chemistry of hydrothermal emissions. Marine-based instruments are typically deployed in campaign-style networks with no real-time telemetry owing to cost considerations and technical limitations. However, when necessary, marine instruments can be operated in real time using cables to transmit data to land-based facilities; other technologies for this purpose are in use or in development, such as acoustic transmission from the instrument to a moored buoy (Matsumoto and others, 2016) and a winch-based system with a satellite antenna that is part of the instrument mooring (Matsumoto and others, 2019). Emerging technologies for marine-based monitoring may be considered as part of a future monitoring plan. These technologies include ocean gliders and floats with on-board hydrophones that have been used to record earthquakes and submarine eruptions (for example, Matsumoto and others, 2013; Sukhovich and others, 2015) and fiber-optic cables that have been used as strainmeters to detect earthquakes (for example, Marra and others, 2018; Lindsey and others, 2019). Land-based instruments and satellites can also provide some capability for monitoring submarine volcanoes, but they provide more limited observations than marine-based instrumentation.

Scientific Investigations Report

Critical minerals in zinc ore—An update on Earth Mapping Resources Initiative Research in the Boulder Batholith region, Montana

Plain Language Summary U.S. Geological Survey research, in collaboration with Montana Technical University and Montana Bureau of Geology and Mines, is providing key critical mineral information that may have potential for critical mineral production of several mining districts in the Boulder Batholith region, to better understand the abundance and distribution of natural resources within this region. Continued research can be used to show the potential for previously undiscovered critical mineral resources in southwestern Montana and in other parts of the United States.

Montana

Emergent headwater types for watershed monitoring, research, and planning

Headwaters—that is headwater streams and the watersheds they drain—strongly influence water quality, ecosystem services, and hydrologic connectivity, yet remain poorly mapped, monitored, and understood at large spatial scales. Using available spatial data to classify headwater “types” could therefore enhance the utility of sparse monitoring data to advance research and watershed planning—and help update literature-based perceptual models of headwaters as steep, forested, and minimally disturbed watersheds. Here, we analyze headwaters across the contiguous United States to quantify how their attributes (climate, topography, land cover, soils) vary regionally and differ from their downstream watersheds. Our analysis (a) identified seven dominant headwater types with distinct combinations of biophysical and climatic attributes and (b) revealed systematic contrasts with downstream watersheds, with strongest differences in attributes representing potential flowpath depth. Our findings offer a transferable framework for classifying, modeling, and managing these critical yet understudied components of the hydrologic network.

conterminous United States

Streamflow depletion caused by groundwater pumping: Fundamental research priorities for management-relevant science

Reductions in streamflow caused by groundwater pumping, known as “streamflow depletion,” link the hydrologic process of stream-aquifer interactions to human modifications of the water cycle. Isolating the impacts of groundwater pumping on streamflow is challenging because other climate and human activities concurrently impact streamflow, making it difficult to separate individual drivers of hydrologic change. In addition, there can be lags between when pumping occurs and when streamflow is affected. However, accurate quantification of streamflow depletion is critical to integrated groundwater and surface water management decision making. Here, we highlight research priorities to help advance fundamental hydrologic science and better serve the decision-making process. Key priorities include (a) linking streamflow depletion to decision-relevant outcomes such as ecosystem function and water users to align with partner needs; (b) enhancing partner trust and applicability of streamflow depletion methods through benchmarking and coupled model development; and (c) improving links between streamflow depletion quantification and decision-making processes. Catalyzing research efforts around the common goal of enhancing our streamflow depletion decision-support capabilities will require disciplinary advances within the water science community and a commitment to transdisciplinary collaboration with diverse water-connected disciplines, professions, governments, organizations, and communities.

Water Resource Research

U.S. Geological Survey research and assessments supporting carbon dioxide removal

Both carbon capture and storage (CCS) and carbon dioxide removal (CDR) are methods to limit future global temperature rise and ocean acidification. CCS sequesters (stores) carbon dioxide (CO2) captured from industrial sources thereby preventing the CO2 from reaching the atmosphere. The captured CO2 is injected into underground geologic reservoirs or is converted into stable industrial products. CDR enhances natural processes or uses technical approaches to remove excess CO2 from the atmosphere. Carbon dioxide is sequestered in natural sinks such as vegetation and soil, or injected into underground reservoirs or converted into durable products. The U.S. Geological Survey (USGS) conducts research and resource assessments that support biologic and geologic CDR approaches. This report will review some of the ongoing USGS CDR research and assessment efforts.

Conference Paper

The Sand AbrasioN Device for Aeolian Research (SANDAR): A new experimental device for investigating how wind transport affects sand on Earth and Mars

On Earth and Mars, aeolian transport causes sand grains to become abraded, resulting in mineralogic and textural changes. Understanding how sands evolve, or mature, with transport via experimental studies is important for understanding the origins, geologic history, and cycling of sediments, as well as dust production. Previous experimental works have used a variety of methods to simulate aeolian transport in the laboratory, but practical limitations and similitude concerns have limited such research. Here, we present and validate the Sand AbrasioN Device for Aeolian Research (SANDAR), a modified air mill that uses pressurized air to circulate sand around a small abrasion chamber, simulating the effects of aeolian transport. This device is re-circulating to simulate long-distance transport, and it allows for repeated analyses of well-constrained sediment samples, revealing their evolution over time. It is compatible with the grain sizes (74–500 μm) and grain impact velocities (∼0.6–3.7 m/s) typically expected for natural aeolian environments, and is also adaptable for diverse applications simulating different wind conditions. We show that the SANDAR achieves similitude of kinetic energy with respect to saltating sand on both Earth and Mars. SEM and optical microscope imaging reveal that the SANDAR produces microtextures on the surfaces of sand grains similar to those found with natural aeolian transport, demonstrating that it effectively simulates the mechanical effects of aeolian processes. Thus, the SANDAR is a valid tool for use in experimental research to improve our understanding of sedimentary processes across the Solar System.

Aeolian Research

Engineering and risk research—A strategic vision for extending USGS earthquake science to risk assessment and mitigation

As a part of the U.S. Geological Survey (USGS) Natural Hazards Mission Area, the Engineering and Risk Project (ERP) of the Geologic Hazards Science Center conducts civil engineering research to extend natural hazards science to risk assessments. The ERP includes predominantly, but not exclusively, staff funded by the USGS Earthquake Hazards Program. A major focus of the ERP is to deliver actionable information to decisionmakers that helps promote the safety, security, and economic well-being of the Nation. The report discusses briefly the ERP’s evolution and scope, its organization structure, describes key products and deliverables, their efforts to engage with external partners, and its strategy and vision in conducting range of engineering and risk research. The research topics outlined in this report, as developed by the ERP, may be used to facilitate project planning activities during the next 10 years and serve as a longer-term planning resource for the USGS Earthquake Hazards Program and Geologic Hazards Science Center.

Circular

Fiber-optic sensing for earthquake hazards research, monitoring and early warning

The use of fiber‐optic sensing systems in seismology has exploded in the past decade. Despite an ever‐growing library of ground‐breaking studies, questions remain about the potential of fiber‐optic sensing technologies as tools for advancing if not revolutionizing earthquake‐hazards‐related research, monitoring, and early warning systems. A working group convened to explore these topics; we comprehensively examined the application of fiber optics in various aspects of earthquake hazards, encompassing earthquake source processes, crustal imaging, data archiving, and technological challenges. There is great potential for fiber‐optic systems to advance earthquake monitoring and understanding, but to fully unlock their capabilities requires continued progress in key areas of research and development, including instrument testing and validation, increased dynamic range for applications focused on larger earthquakes, and continued improvement in subsurface and source imaging methods. A key current stumbling block results from the lack of clear data archiving requirements, and we propose an initial strategy that balances data volume requirements with preserving key data for a broad range of future studies. In addition, we demonstrate the potential for fiber‐optic sensing to impact monitoring efforts by documenting the data completeness in a number of long‐term experiments. Finally, we outline the features of a instrument testing facility that would enable progress toward reliable and standardized distributed acoustic sensing data. Overcoming these current obstacles would facilitate progress in fiber‐optic sensing and unlock its potential application to a broad range of earthquake hazard problems.

California, Oregon, Washington

Top Elevation of Glacial Till and Thickness of the Big Sioux Aquifer Delineated From Electrical Resistivity Tomography Surveys Near Sioux Falls, South Dakota, 2022 and 2025

The City of Sioux Falls, South Dakota, requested the U.S. Geological Survey perform electrical resistivity surveys on three parcels of land north of the city. Electrical resistivity data were collected along a total of 22 transects during March 14–18, 2022, and November 17–21, 2025. Results from electrical resistivity surveys were used to delineate the top of glacial till deposits for the purpose of characterizing the Big Sioux aquifer near the city. Delineating geologic contacts provides important information on groundwater storage, flow dynamics, well design and placement, contaminant transport, groundwater–surface-water interactions, and regional water modeling. The top elevation of glacial till and the thickness of the Big Sioux aquifer varied among the three survey areas. The interpreted top elevation of glacial till in the North survey area decreases from east to west toward a slough, with elevations ranging from 1,403 to 1,418 feet (ft). The estimated thickness of the Big Sioux aquifer in the North survey area increased from east to west, with thicknesses ranging from 23 to 38 ft. The top elevation of glacial till in the Well 72 survey area generally decreases from northwest to southeast. Top elevations of the glacial till in the Well 72 survey area ranged from 1,400 to 1,409 ft along the southern end of transect W72_2. The estimated thickness of the Big Sioux aquifer in the Well 72 survey area was greatest along a southeast to northwest trending channel, with thicknesses ranging from 28 to 40 ft. The top elevation of glacial till in the Nose survey area generally decreases west toward the Big Sioux River. Top elevations of the glacial till in the Nose survey area ranged from 1,362 to 1,395 ft. The estimated thickness of the Big Sioux aquifer in the Nose survey area ranged from 33 to 70 ft.

South Dakota

40Ar/39Ar geochronology supporting mineral resources research at USGS Denver

The 40 Ar/ 39 Ar geochronology method is used to date potassium-bearing rocks and minerals, based on the decay of 40 K to 40 Ar, which provides important temporal constraints for geological events. The USGS Denver Argon Geochronology Laboratory dates samples from a variety of projects, mainly in the USGS Mineral Resource Program and the National Cooperative Geologic Mapping Program, facilitating in-depth research into the timing of geological events and processes. Recent applications of this method include geochronological studies in the Yellow Pine district, revealing mineralization ages that range from 51 to 70 Ma, and investigations into the Bear Lodge alkaline complex, providing insights into the timing of REE carbonatite formation. Additionally, studies at Alunite Ridge highlight the method's potential for understanding concealed mineral deposits. Ongoing projects continue to leverage 40 Ar/ 39 Ar data to enhance understanding of geologic frameworks and mineral resources, underpinning its importance in modern geochronology and mineral resource assessment.

Conference Paper

Hydrogeologic conceptualization of the Arroyos subarea and Northeast Air Force Research Laboratory subarea of the Air Force Research Laboratory, Edwards Air Force Base, Antelope Valley, California, 2017–21

Research and testing within the Air Force Research Laboratory at Edwards Air Force Base in the southwestern Mojave Desert has been conducted since the 1950s. This testing requires large quantities of groundwater for cooling and operations involving hazardous constituents that have entered the groundwater. To better understand the potential movement of contaminants through the groundwater system, the U.S. Geological Survey entered into a cooperative agreement with the U.S. Air Force Civil Engineer Center with the purpose of (1) gaining a more detailed understanding of the hydraulic connection between the unconsolidated basin-fill sediment and the underlying weathered and crystalline bedrock and (2) investigating faults and their potential effect on groundwater flow. This study was specific to the Arroyos subarea and Northeast Air Force Research Laboratory subarea of the Air Force Research Laboratory. The refined hydrogeologic characterization was derived by evaluating surface geologic maps, a regional gravity model, new subsurface geophysical surveys, lithology data from boreholes, and groundwater-level data. Refinement of the hydrogeologic characterization of the study area involved developing a map of basin-fill sediment thickness, estimating the geometry and depth to bedrock, determining the presence of weathered bedrock material, and identifying the location of faults and subsurface structures. The thickness of basin-fill sediment was derived from a regional gravity model. Basin-fill sediment ranges from less than 20 feet (ft) thick to about 150 ft thick and increases substantially toward a deep structural basin in the northwestern part of the study area. The top of bedrock estimated from the new surface geophysical surveys is generally deeper than the top of bedrock from the regional gravity model. These differences in interpreted bedrock tops indicate that there may be a zone of weathered bedrock in the subsurface, overlying crystalline bedrock. Additional subsurface data evaluating the geometry and thickness of weathered bedrock are necessary for a comprehensive evaluation of weathered bedrock in the study area. Previously unmapped extensions of the Leuhman Fault, Spring Fault Zone, and Boron Gate Fault were identified in the new surface geophysical surveys. Evaluation of groundwater flow between bedrock and basin-fill sediment, and the effects of faults on groundwater flow, was done using groundwater-level data from 2020. The groundwater table was in crystalline bedrock throughout most of the Arroyos and Northeast Air Force Research Laboratory subareas, with a few exceptions where it was in basin-fill sediment and weathered bedrock. Basin-fill sediment, and likely weathered bedrock, was partially saturated in parts of the study area where basin-fill sediment was as thick as 150 ft. Weathered bedrock material may be present near the Spring Fault Zone, and if so, was likely saturated in 2020. The groundwater-level data near and within Spring Fault Zone indicate that the Spring Fault Zone acts as a vertical-along-strike conduit for, and as an across-strike impediment to, groundwater flow. In addition, steep groundwater-level gradients in the southeastern part of the study area indicate that a subsurface structure affecting groundwater flow could be related to the Leuhman Fault. Sufficient groundwater-level data were not available to conclusively determine if the Arroyos, Rich, and Boron Gate Faults, and their inferred extensions from the geophysical surveys, affect the movement or direction of groundwater flow.

California

Development of a hydrologic flow model of the Zuñi Salt Lake and surrounding areas, west-central New Mexico

The terminal Zuñi Salt Lake is in a maar in west-​central New Mexico and contains hypersaline water that has long been used by Native Americans for religious purposes and the collection of salt. The U.S. Geological Survey (USGS), in cooperation with the Zuni Tribe of the Zuni Reservation, New Mexico, and Bureau of Reclamation, developed the Zuñi Salt Lake hydrologic flow model to simulate the steady-state conditions of the lake and surrounding groundwater-flow system. The model is a tool that can be used to analyze the potential hydrologic responses to resource development in the region under different water-use scenarios, which can support negotiations that could help protect future use of the lake. The USGS modular hydrologic model, MODFLOW 6, was used to simulate the hydrologic system of the lake and surrounding areas. To define the layering of the model, a three-dimensional hydrogeologic framework was constructed, which included seven informal hydrogeologic units and the locations of faults that truncate and offset the units. Calibration of the model was performed using the iterative ensemble smoother included in a parameter estimation software suite (PEST++). The iterative ensemble smoother approach resulted in a posterior parameter ensemble of model realizations with parameter and simulated values that show similar success in matching observations. Groundwater flux to the Zuñi Salt Lake simulated by using the posterior parameter distribution ranged from 26 to 730 acre-feet per year with a mean, median, and standard deviation of 530, 570, and 170 acre-feet per year, respectively. The relative contribution of groundwater discharge to the lake was simulated using a particle-tracking model for MODFLOW (MODPATH) to be from, in order of decreasing contribution, the Mesaverde, Cenozoic, Mancos, and Dakota hydrogeologic units. Simulations of future conditions using the ensemble of models can provide an empirical estimate of forecast uncertainty without substantial additional analysis.

New Mexico

Sources of water and salts for the Zuni Salt Lake in west-central New Mexico

The Zuni Salt Lake is located in a maar in west-central New Mexico and contains hypersaline water that has long been used by Native Americans for religious purposes and the collection of salt. There have been several investigations suggesting different sources for the water and salt to the lake. Springs, seeps, and ephemeral streamflow have all been observed to contribute freshwater to the lake, and brackish to hypersaline seeps have been documented along the banks of the lake. This report summarizes the findings of a study that characterizes the lake’s hydrology, its water and salinity sources, and the hydrogeologic conceptual model. Regional groundwater levels indicate that each of the aquifers in the area have the potential to discharge groundwater to the lake. There is also evidence of vertical groundwater flow pathways at the maar that were likely created by the igneous intrusion that fractured the intersecting aquifers. A detailed water budget was constructed from continuous lake stage, precipitation, and evaporation data to estimate the groundwater inflow to the Zuni Salt Lake. It was determined that groundwater inflow to the lake is 441 ±94 acre-feet per year, which composes as much as 77 percent of the total inflows. The high sodium and chloride concentrations measured in two hypersaline samples collected near the lake indicate that the majority of the dissolved solids entering the lake are from a hypersaline groundwater source. The geochemical and isotopic compositions measured in the lake and surrounding features support the interpretation that hypersaline groundwater is the primary source of salts to the lake, which is likely sourced from the older (and deeper) Permian units. The hypersaline groundwater samples collected during this investigation have a unique aqueous chemistry relative to each of the mapped aquifers, and variability in groundwater compositions is interpreted to result from differences in minerology and residence time.

New Mexico

Special issue "Effects of surface geology on seismic motion (ESG): General state-of-research"

To understand and predict the behaviors of strong ground motions incurred during devastating earthquakes, studies focused on the “effects of surface geology (ESG) on seismic motions” (following tradition, herein contracted as: “ESG”) have progressed steadily in the last three decades. These ESG studies typically involve in situ measurements of the wavefield and commonly apply both analytical and computational approaches. Concurrently, improvements in ESG related research can be readily attributed to the proliferation of openly accessible strong motion data, as well as advances in computational power. Nevertheless, there remain significant shortfalls in our understanding of the epistemic and aleatory uncertainties associated with the ESG as demonstrated by phenomena from recent deadly earthquake-related site effects. Thus, investigations toward addressing these deficiencies should be underscored in future earthquake related disaster mitigation efforts. This special issue of Earth, Planets, and Space (EPS) is dedicated to the ongoing efforts by the International Association of Seismology and Physics of the Earth’s Interior (IASPEI) and the International Association of Earthquake Engineering (IAEE) that champion activities promoting studies related to the ESG.

Earth, Planets and Space

A multidisciplinary approach that considers occurrence, geochemistry, bioavailability, and toxicity to prioritize critical minerals for environmental research

Critical minerals (or critical elements) are minerals or elements that are essential to global security and development and have supply chains vulnerable to disruption. In general, knowledge of the environmental behavior and health effects of critical elements is needed to support the development of safe and environmentally responsible supplies. This knowledge includes identifying potential consequences of increased critical element production and use, alternative critical element sources such as mine wastes, and adverse effects of critical elements on ecosystem condition and organismal health. Here we identify significant data gaps in the understanding of critical elements in surficial and aquatic environments, and the need, given the large number of commodities (50) identified on the 2022 critical minerals list for the United States, for an approach to prioritize them for study of their environmental fate and effects. We propose a multidisciplinary approach for this prioritization, considering measures of occurrence, geochemistry, bioavailability, and toxicity. We describe relatively easy-to-obtain metrics for each of these topic areas and demonstrate the utility of this integrated prioritization approach using indium and zinc as examples. This approach facilitates prioritizing research with a focus on those critical elements that are most mobile in the environment, bioavailable, toxic, or simply lacking data in these categories.

Environmental Science & Technology