Implementing a Community-Led Arsenic Mitigation Intervention for Private Well Users in American Indian Communities: A Qualitative Evaluation of the Strong Heart Water Study Program

Arsenic is a naturally occurring toxicant in groundwater, which increases cancer and cardiovascular disease risk. American Indian populations are disproportionately exposed to arsenic in drinking water. The Strong Heart Water Study (SHWS), through a community-centered approach for intervention development and implementation, delivered an arsenic mitigation program for private well users in American Indian communities. The SHWS program comprised community-led water arsenic testing, point-of-use arsenic filter installation, and a mobile health program to promote sustained filter use and maintenance (i.e., changing the filter cartridge). Half of enrolled households received additional in-person behavior change communication and videos. Our objectives for this study were to assess successes, barriers, and facilitators in the implementation, use, and maintenance of the program among implementers and recipients. We conducted 45 semi-structured interviews with implementers and SHWS program recipients. We analyzed barriers and facilitators using the Consolidated Framework for Implementation Research and the Risks, Attitudes, Norms, Abilities, and Self-regulation model. At the implementer level, facilitators included building rapport and trust between implementers and participating households. Barriers included the remoteness of households, coordinating with community plumbers for arsenic filter installation, and difficulty securing a local supplier for replacement filter cartridges. At the recipient level, facilitators included knowledge of the arsenic health risks, perceived effectiveness of the filter, and visual cues to promote habit formation. Barriers included attitudes towards water taste and temperature and inability to procure or install replacement filter cartridges. This study offers insights into the successes and challenges of implementing an arsenic mitigation program tailored to American Indian households, which can inform future programs in partnership with these and potentially similar affected communities. Our study suggests that building credibility and trust between implementers and participants is important for the success of arsenic mitigation programs.

A study of iodine concentration in drinking waters of Bryansk and Oryol regions

The aim of the research was to study and compare iodine concentration in natural waters originating from aquifers of different ages, primarily residents use for drinking purposes. The analysis was based on the original data on the samples collected during the fieldwork in the Bryansk region (2013-2017) and in the Oryol region (2016-2017). In addition to iodine concentration, the main geochemical parameters (salinity, etc.) were determined in the selected waters. The results showed a significant variation of iodine in waters from both regions (Bryansk region-from 0.7 to 41.2 µg/l; Oryol region-from 1.12 to 36.8 µg/l), the difference being apparently due to different ages and origins of the sampled aquifers (Quaternary, Upper Devonian and Cretaceous deposits). The overall low provision of surface water with iodine was found both in the Bryansk region (median for shallow wells-5.82 µg/l, median for surface water-6.76 µg/l) and in the Oryol region (median for shallow wells-2.96 µg/l, median for surface water-7.4 µg/l). The data obtained deserve attention during organization of monitoring and implementation of measures preventing thyroid diseases.

Drinking Water From Private Wells and Risks to Children

Drinking water for approximately 23 million US households is obtained from private wells. These wells can become contaminated by pollutant chemicals or pathogenic organisms, leading to significant illness. Although the US Environmental Protection Agency and all states offer guidance for construction, maintenance, and testing of private wells, most states only regulate the construction of new private water wells. With a few exceptions, there is little regulation after construction. Well owners are responsible for their own wells. Children may also drink well water at child care or when traveling. Illness resulting from children’s ingestion of contaminated water can be severe. This report reviews relevant aspects of groundwater and wells; describes the common chemical and microbiologic contaminants; gives an algorithm with recommendations for inspection, testing, and remediation for wells providing drinking water for children; and provides references and Internet resources for more information.

Drinking Water From Private Wells and Risks to Children

Drinking water for >23 million US households is obtained from private wells. These wells can become contaminated by chemicals, naturally occurring toxic substances, or pathogenic organisms that can cause illness in children. Although the US Environmental Protection Agency and most states offer some guidance for the construction, maintenance, and testing of private wells, most states only regulate the construction of new private water wells. With few exceptions, well owners are responsible for their own wells after the initial construction. Children may also drink well water at childcare or when traveling. This policy statement provides recommendations for the inspection, testing, and remediation of private wells to provide safe drinking water for children.

Revealing the sources of arsenic in private well water using Random Forest Classification and Regression

Exposure to arsenic through private drinking water wells causes serious human health risks throughout the globe. Water testing data indicates there is arsenic contamination in private drinking water wells across New Jersey. To reduce the adverse health risk due to exposure to arsenic in drinking water, it is necessary to identify arsenic sources affecting private wells. Private wells are not regulated by any federal or state agencies through the Safe Drinking Water Act and therefore information is often lacking. To this end, we have developed machine learning algorithms including Random Forest Classification and Regression to decipher the factors contributing to higher arsenic concentration in private drinking water wells in west-central New Jersey. Arsenic concentration in private drinking water wells served as a response variable while explanatory variables were geological bedrock type, soil type, drainage class, land use/cover, and presence of orchards, contaminated sites, and abandoned mines within the 152.4-meter (500 ft) radius of each well. Random Forest Classification and Regression achieved 66 % and 55 % prediction accuracies for arsenic concentration in private drinking water wells, respectively. Overall, both models identify that bedrock, soil, land use/cover, and drainage type (in descending order) are the most important variables contributing to higher arsenic concentration in well water. These models further identify bedrock subgroups at a finer scale including Passaic Formation, Lockatong Formation, Stockton Formation contributing significantly to arsenic concentration in well water. Identification of sources of arsenic contamination in private drinking water wells at such a fine scale facilitates development of more targeted outreach as well as mitigation strategies to improve water quality and safeguard human health.

GIS-based multi-criteria decision-making techniques and analytical hierarchical process for delineation of groundwater potential

The profound knowledge and management of groundwater resources is a prerequisite in order to ensure the sustainability of these resources. In this research, multi-criteria decision-making (MCDM) and analytical hierarchical process (AHP) method based on GIS were used to determine the groundwater potential recharge model of the Mornag plain (coastal area in North Tunisia). Influential eight factors were used in the groundwater recharge modeling: lithology, land use/land cover, hydrogeomorphology, elevation, rainfall, drainage density, lineament density, and soil. The influence of each factor was examined by the weighted linear combination method. The results reveal a very high to high groundwater recharge potential in the order of 20% of the total area. The validation of results by the histogram method showed that 41% of the total area corresponds to the moderate to very high recharge potential classes. The groundwater recharge potential model (GIS-MCDM-AHP) is useful in better management and planning of groundwater resources and implementation of wells and hydraulic structures in arid and semi-arid areas.

Factoring Impacts to Water Supply Well Operations into Groundwater Management Planning

Groundwater management planning requires balancing the interests of different stakeholder groups because (1) water supply development causes changes to groundwater systems that include declines in groundwater levels and (2) benefits and costs from pumping the common-pool resource often do not occur such that they are shared proportionate to use. Quantifying impacts from declining groundwater levels among user groups can be useful for evaluating management strategies. In California, considering impacts to supply well operations is proving important for acceptance of management plans that have been required by law. A case study is presented to illustrate the types of results that may contribute to the planning process. The results indicate that significant differences in impact may occur between groundwater pumpers. Suggestions are provided for using this information to mitigate impacts to the most vulnerable stakeholders.

Using Alternate Pumping and Cooperative Game Theory to Reduce Sea Water Intrusion

In this article, alternate pumping is studied as a means used to reduce the salinity concentration in coastal aquifers, pumped using a system of wells. This approach has been applied to a hypothetical confined coastal aquifer. Flow has been modeled, using SEAWAT. Two strategies are proposed based on cooperative game theory, to promote alternate pumping. In both strategies an external player will compensate the users that will pump during an unpopular pumping period. In the first strategy it is supposed that this external player aims at protecting a critical well, e.g. a municipal well, reducing its maximum salinity concentration by pumping alternately. In the second strategy proposed, the target is to reduce the overall salinity of the water pumped by the wells. In applying the cooperative game theory, the Shapley value is used to distribute the benefits of cooperation between the players (well users), according to their marginal contribution. Overall, well users can reduce sea water intrusion by cooperatively changing their pumping time schedules. The game theoretical model developed is a useful tool to promote cooperation toward this direction. The methods applied in the hypothetical aquifer, can be tested in actual aquifers to reduce sea water intrusion.

In-Well Degassing of Monitoring Wells Completed in Gas-Charged Aquifers

Total dissolved gas pressure (P_TDG ) measurements are useful to measure accurate in situ dissolved gas concentrations in groundwater, but challenged by in-well degassing. Although in-well degassing has been widely observed, its cause(s) are not clear. We investigated the mechanism(s) by which gas-charged groundwater in a recently pumped well becomes degassed. Vertical P_TDG and dissolved gas concentration profiles were monitored in the standing water column (SWC) of a groundwater well screened in a gas-charged aquifer for 7 days before and 15 days after pumping. Prior to pumping, P_TDG values remained relatively constant and below calculated bubbling pressure (P_BUB ) at all depths. In contrast, significant increases in P_TDG were observed at all depths after pumping was initiated, as fresh groundwater with elevated in situ P_TDG values was pumped through the well screen. After pumping ceased, P_TDG values decreased to below P_BUB at all depths over the 15-day post-pumping period, indicating well degassing was active over this time frame. Vertical profiles of estimated dissolved gas concentrations before and after pumping provided insight into the mechanism(s) by which in-well degassing occurred in the SWC. During both monitoring periods, downward mixing of dominant atmospheric and/or tracer gases, and upwards mixing of dominant groundwater gases were observed in the SWC. The key mechanisms responsible for in-well degassing were (i) bubble exsolution when P_TDG exceeded P_BUB as gas-charged well water moves upwards in the SWC during recovery (i.e., hydraulic gradient driven convection), (ii) microadvection caused by the upward migration of bubbles under buoyancy, and (iii) long-term, thermally driven vertical convection.

Targeted Private Well Outreach Following a Change in Drinking Water Standard: Arsenic and the New Jersey Private Well Testing Act

CONTEXT

When the New Jersey Private Well Testing Act (PWTA) became effective in 2002, the maximum contaminant level (MCL) for arsenic in the United States was 50 μg/L. In 2006, the federal and New Jersey MCLs were lowered to 10 μg/L and 5 μg/L, respectively.

OBJECTIVE

To notify and provide free arsenic water testing for homeowners who had a PWTA arsenic result that passed for the MCL in 2006 or earlier but would exceed under the more health protective MCL enacted in 2006, which is still in effect as of this publication date.

DESIGN

About 1200 homeowners with PWTA arsenic results between 5 μg/L and 50 μg/L were offered free arsenic water testing. More than 400 homeowners requested tests and 292 returned samples.

SETTING

New Jersey, United States.

PARTICIPANTS

Homeowners with a passing PWTA arsenic result before 2006 that would have failed under the New Jersey arsenic MCL enacted in 2006.

MAIN OUTCOME MEASURES

Return rate of testing kits; number of tests exceeding arsenic MCL; and participant survey results.

RESULTS

Untreated well water samples (n = 279) were collected and 62.4% exceeded the New Jersey MCL. Treated well water samples (n = 102) were collected and 11.8% exceeded the current New Jersey MCL. In all, about 40% of drinking water samples from the tap, including those with or with no arsenic treatment, exceeded the New Jersey MCL. A survey of participants (n = 69) found that although many (67%) respondents reported that they at least had some idea that wells in their area are vulnerable to naturally occurring contaminants, such as arsenic, many (68%) reported that they had little or no idea that the New Jersey arsenic MCL had been lowered from 50 μg/L to 5 μg/L in 2006.

CONCLUSIONS

This effort further illuminates the necessity and significance of public health outreach for private well water users, especially after drinking water standards change.

Modeling demonstrates minimal ecological risks of cuttings discharges associated to oil and gas drilling with deep water wells

To assess the impacts of drill cutting discharges in the Gulf of Mexico, a particle dispersion modeling study was conducted on hypothetical drilling scenarios. The goal was to assess cumulative seabed deposition, and potential hydrocarbon loading from non-aqueous drilling fluids (NADF). Cuttings drilled with NADF showed to have minimal impact on local fauna at the deep-water well simulated. A hypothetical drill site was modeled under 3 different seasonally representative met-ocean conditions. The site is located approximately 260 km from the coast in water roughly 3500 meters (m) deep. Cumulative deposition was assessed for all materials released, whereas hydrocarbon loading was assessed based on the potential for NADF fluids to be retained on cuttings. Smothering effects on the benthic community are not anticipated. Hydrocarbon deposition was also very limited, ≤165 ppm of TPH. Overall, the cuttings drilled with NADF are predicted to have minimal impact on local fauna.

Evaluation the feasibility of using clinoptilolite as a gravel pack in water wells for removal of lead from contaminated groundwater

The ability of clinoptilolite zeolite as a filter in water wells to remove lead from polluted groundwater was tested in batch and fixed-bed column experiments. XRF, XRD, SEM, and BET were used to characterize the zeolite. Because of the pH variation in groundwater, batch experiments were performed at pH = 6, 7, and 8, with the highest removal efficiency (84.2%) at pH = 6 and 298 K within 90 min. The Freundlich model accurately predicted metal ion adsorption behavior and indicated a multilayer adsorption of Pb(II) molecules on the inhomogeneous surface of clinoptilolite. The best-fitting kinetic model for clinoptilolite is the pseudo-second order equation, highlighting that the rate of adsorption is dependent on absorbent capacity. Next, the effect of flow rate, bed depth, and grain size of clinoptilolite on lead removal was investigated in column experiments at an initial concentration of 450 mg pb/L. The highest removal efficiency was achieved in column experiments with a flow rate of 1 mL/min, a bed height of 10 cm, and a grain size of 0.6 to 0.8 mm. Breakthrough curves were predicted by the Thomas and Yoon-Nelson models, with excellent agreement with the corresponding experimental data. This research will be used to develop a new in situ remedial approach for removing lead from polluted groundwater.

Naturally occurring metals in unregulated domestic wells in Nevada, USA

The dominant source of drinking water in rural Nevada, United States, is privately-owned domestic wells. Because the water from these wells is unregulated with respect to government guidelines, it is the owner's responsibility to test their groundwater for heavy metals and other contaminants. Arsenic, lead, cadmium, and uranium have been previously measured at concentrations above Environmental Protection Agency (EPA) guidelines in Nevada groundwater. This is a public health concern because elevated levels of these metals are known to have negative health effects. We recruited individuals through a population health study, the Healthy Nevada Project, to submit drinking water samples from domestic wells for testing. Water samples were returned from 174 households with private wells. We found 22 % had arsenic concentrations exceeding the EPA maximum contaminant level (MCL) of 10 μg/L. Additionally, federal, state, or health-based guidelines were exceeded for 8 % of the households for uranium and iron, 6 % for lithium and manganese, 4 % for molybdenum, and 1 % for lead. The maximum observed concentrations of arsenic, uranium, and lead were ∼80, ∼5, and ∼1.5 times the EPA guideline values, respectively. 41 % of households had a treatment system and submitted both pre- and post-treatment water samples from their well. The household treatments were shown to reduce metal concentrations, but concentrations above guideline values were still observed. Many treatment systems cannot reduce the concentration below guideline values because of water chemistry, treatment failure, or improper treatment techniques. These results show the pressing need for continued education and outreach on regular testing of domestic well waters, proper treatment types, and health effects of metal contamination. These findings are potentially applicable to other arid areas where groundwater contamination of naturally occurring heavy metals occurs.

Composition and Origin of Surface Casing Fluids in a Major US Oil- and Gas-Producing Region

Fluids leaked from oil and gas wells often originate from their surface casing─a steel pipe installed beneath the deepest underlying source of potable groundwater that serves as the final barrier around the well system. In this study, we analyze a regulatory dataset of surface casing geochemical samples collected from 2573 wells in northeastern Colorado─the only known publicly available dataset of its kind. Thermogenic gas was present in the surface casings of 96.2% of wells with gas samples. Regulatory records indicate that 73.3% of these wells were constructed to isolate the formation from which the gas originated with cement. This suggests that gas migration into the surface casing annulus predominantly occurs through compromised barriers (e.g., steel casings or cement seals), indicative of extensive integrity issues in the region. Water was collected from 22.6% of sampled surface casings. Benzene, toluene, ethylbenzene, and xylenes were detected in 99.7% of surface casing water samples tested for these compounds, which may be due to the presence of leaked oil, natural gas condensate, or oil-based drilling mud. Our findings demonstrate the value of incorporating surface casing geochemical analysis in well integrity monitoring programs to identify integrity issues and focus leak mitigation efforts.

Characterizing regional radon-in-air levels in rocks of the Canary Islands (Spain): new data and results

In this work, a regional-scale strategy to characterize the radon activity levels in the Canary Islands (Spain) is described. The main objectives of this strategy consisted of (1) studying the likely relationship between radon concentration and lithology of the rock matrix through the lithological data of 247 samples from volcanic rocks of the Canary Islands and (2) implementing a series of monitoring sites in the form of boreholes and wells to study the evolution of radon-in-air activity on a daily to yearly timescale.

Assessing the protective effect of cutoff walls on groundwater pumping against saltwater upconing in coastal aquifers

Subsurface physical barriers are amongst the most effective methods to mitigate seawater intrusion in coastal aquifers. The main objective of this study was to examine the impact of cutoff walls on saltwater upconing using laboratory and numerical modelling experiments. Physical experiments were first completed to reproduce the saltwater upconing process in a laboratory-scale coastal aquifer model incorporating an impermeable cutoff wall. Numerical modelling was used for validation purposes and to perform additional simulations to explore the protective effect of cutoff walls against saltwater upconing. The results suggest that the cutoff wall did not substantially delay the saltwater upconing mechanism in the investigated configurations. Laboratory and numerical observations showed the existence of some residual saline water, which remained on the upper part of the aquifer on the seaward side of the wall following the retreat of the saltwater. The protective effect of cutoff walls was noticeably sensitive to the design parameters. Specifically, cutoff walls installed close to the pumping well enabled the implementation of higher pumping rates, therefore a more optimal use of the freshwater, especially for deeper wells. The results highlighted that the penetration depth of the cutoff walls may not necessarily need to exceed the depth of the pumping well to ensure effectiveness, which is of great importance from construction and economic perspectives.

Temporal evolution of organochlorine and organophosphate pesticide residues in wells in the Akkar Region (Lebanon)

The Akkar plain is the second largest agricultural area in Lebanon. This region produces huge amount of regular crops such as maize, fruits, and vegetables. In order to protect the crops, farmers use large quantities of many pesticides (including authorized and prohibited molecules) without respecting the recommended doses. In this work, we wanted to study the evolution of OCP and OPP residues at 3-year intervals in water wells in the Akkar region. Twenty OCPs and 8 OPPs were monitored in eight wells in different villages in the plain and mountains of Akkar. Solid phase extraction (SPE) method was used for pesticide extraction, followed by gas chromatography-mass spectrometry (GC-MS) analysis. The results revealed an increasing concentration of OCPs and OPPs in groundwater over the last 3 years (between 2017 and 2019-2020). This increase in contamination is due to the uncontrolled and still unregulated (by the authorities) use of pesticides, and also to the introduction of new crops. The concentrations found in groundwater confirm that some banned pesticides are still widely used. The calculation of the theoretical pesticide intake suggests that pesticide concentrations in Akkar represent a greater health risk for the population consuming well water during the rainy season.

Application and comparison of different statistical methods for the analysis of groundwater levels over time: Response to rainfall and resource evolution in the Piedmont Plain (NW Italy)

Monitoring and analysis of groundwater level (GWL) in space and time is one of the tools used to evaluate the quantitative status of groundwater (GW) resources and identify possible alterations and critical cases due to climate change and variability, anthropogenic influences and other driving factors. In this study, four statistical methodologies (trend, change-point, percentile and non-standardized anomaly analyses) were applied for GWL and rainfall (R) analysis in the Piedmont Plain (western Po Plain, NW Italy). To detect the interannual variations in the GW maximum annual amplitude, the coefficient of variation was also used. The aims of the study were 1) to compare the results of different statistical methods, highlighting their applicability and differences to evaluate the quantitative evolution of GW, 2) to identify the relationship between GWL and R, 3) to investigate the spatiotemporal variation in the GWL of shallow aquifers in the Piedmont Plain, and 4) to describe critical situations of GW depletion. The study highlights that the application of a single method for assessing the shallow GW resource status does not always guarantee a reliable evaluation. For this reason, it is advisable to apply different analysis methods at the same time. Completeness of data and medium to long time series are prerequisites for meaningful analyses. The use of the same time interval is always necessary for comparisons between different monitoring wells and between the results of different statistical analyses. Last, by spatializing the results, it was possible to identify areas characterized by similar GWL behaviour due to hydrological structure, climate variability, land use and the evolution of anthropogenic activities over time. These factors influence vary locally in the Piedmont plain and require local assessments to determine the impact of changes in GWL.

An assessment of total coliforms and associated thresholds as water quality indicators using a large Ontario private drinking water well dataset

A spatiotemporally static total coliform (TC) concentration threshold of five colony-forming units (CFU) per 100 mL is used in Ontario to determine whether well water is of acceptable quality for drinking. The current study sought to assess the role of TC and associated thresholds as microbial water quality parameters as the authors hypothesized that, since static TC thresholds are not evidence-based, they may not be appropriate for all well water consumers. A dataset containing the microbial water quality information of 795,023 samples (including TC and Escherichia coli (E. coli) counts) collected from 253,136 private wells in Ontario between 2010 and 2017 was used. To accurately assess the relationship between E. coli and non-E. coli TC, "non-E. coli coliform" (NEC) counts were calculated from microbial water quality data and replaced TC throughout analyses. This study analysed NEC and E. coli detection rates to determine differences between the two, and NEC:E. coli concentration ratios to assess links, if any, between NEC and E. coli contamination. Study findings suggest that spatiotemporally static NEC thresholds are not appropriate because seasonal, spatial, and well-specific susceptibility factors are associated with distinct contamination trends. For example, NEC detection rates exhibited bimodality, with summer (29.4 %) and autumn (30.2 %) detection rates being significantly higher (p < 0.05) than winter (21.9 %) and spring (19.9 %). E. coli detection rates also varied seasonally, but peaked in summer rather than autumn. As such, it is recommended that these factors be considered during the development of private well water guidelines and that static thresholds be avoided. Furthermore, the authors propose that, because NEC:E. coli concentration ratios change in the context of the aforementioned factors, they may have a role in inferring groundwater contamination mechanisms, with high ratios being associated with generalized aquifer contamination mechanisms and low ratios with localized contamination mechanisms.

Assessment of shallow groundwater contamination on Pari Island, Indonesia

Freshwater on small islands is generally limited and relies on rainwater and groundwater. This study aimed to assess changes in shallow groundwater quality on Pari Island, Indonesia. Pari Island is a small island with an area of 41.32 ha and belongs to a monsoon climate. Also, being a residential island, it attracts many tourists. The approach was to assess the shallow groundwater quality of ten wells during the dry and wet seasons. Changes in water quality were evaluated using traditional hydrochemical analysis methods (Schoeller, Piper, and Gibbs diagrams) and ion ratios. Shallow groundwater quality in the study area showed different responses depending on the season. Therefore, each well responded differently to changes represented by changes in water quality. The change is controlled by various factors: evaporation (or water balance), geology, aquifer characteristics, tides, wind direction, and wave height. These factors trigger the fluctuation of groundwater and seawater interface, affecting the amount of rainwater and seawater transported to the freshwater aquifer layer. This water volume transported affects the process of rock weathering, dissolution, and dilution of contaminants in shallow groundwater.

Siwa Oasis groundwater quality: factors controlling spatial and temporal changes

Siwa Oasis is of great historical, environmental, and scientific importance, as it contains unique archeological and geological features. Groundwater is the main source of freshwater in that oasis. The carbonate aquifer groundwater, used for irrigation, was sampled to evaluate factors controlling quality changes spatially and temporally by applying hydrochemical and statistical analyses. The salinity of the aquifer varied spatially from 1367 to 8645 mg/l based on one hydrogeological condition, with the highest TDS (> 5432.5 mg/l, 25% of samples) at the central part of the study area. Temporally, the salinity changed slightly from 3754.3 mg/l (in 2014) to 4222.4 mg/l (in 2020). The cession of illegal wells, pumping control, and excavation of formed salts have a noticeable impact on salinity (mediate the increase in salinity) and ions. However, about 61% of the studied samples can be considered unsuitable for irrigation owing to salinity and can harm plant yield. The heavy metals studied (Fe, Mn, Cu, Pb), except Cd, were within the permissible limit for irrigation water. Finally, it is proposed to construct desalination stations to enhance water quality for irrigation in the study area and set up many companies for salt extraction.

Study on sedimentary facies and prediction of favorable reservoir areas in the Fuyu reservoir in the Bayanchagan area

Based on the study's thorough logging records from 74 wells, grain size analysis, spatial analysis of sand thickness and sand ratio, and pertinent regional geological data, a sedimentary microfacies analysis of the Bayanchagan area is conducted using one sand layer as a unit. In addition, the reservoir's microscopic characteristics are summarized, and the location of advantageous reservoir areas is predicted. The principal reservoir rock types in the research region are determined to be lithic arkose and feldspathic lithic sandstone, and reservoir physical attributes are also quite poor. Intergranular dissolution pores make up the bulk of reservoir space types, which also include primary pores, secondary dissolution pores, and micro-fractures. Additionally, the delta front and delta plain subfacies are recognized. Eight more sedimentary microfacies are found: sheet sand, estuary bar, underwater distributary channel, underwater distributary bay, overflow thin sand, floodplain, and distributary channel under water. In a sedimentary environment with water penetration, the entire reservoir was produced. The delta diversion plain deposit makes up the lower portion of the FIII, FII, and FI oil layer groups, while the delta front deposit makes up the top portion of the FI oil layer group. The reservoirs may be divided into three groups: type I reservoirs, type II reservoirs, and type III reservoirs by thorough examination of the facies, microstructure, mercury intrusion characteristics, and other criteria. Among these, type I and type II reservoirs with substantial thicknesses, which are favorable for hydrocarbon accumulation, are the main focus of favorable oil and gas area exploration. The investigation's conclusions are instructive for future research.

Field Testing of a Novel Drilling Technique to Expand Well Diameters at Depth in Unconsolidated Formations

Larger well diameters allow higher groundwater abstraction rates. But particularly for the construction of wells at greater depth, it may be more cost-efficient to only expand the borehole in the target aquifer. However, current drilling techniques for unconsolidated formations are limited by their expansion factors (<2) and diameters (<1000 mm). Therefore, we developed a new technique aiming to expand borehole diameters at depth in a controlled manner using a low-pressure water jet perpendicular to the drilling direction and extendable by means of a pivoting arm. During a first field test, the borehole diameter was expanded 2.6-fold from 600 to 1570 mm at a depth of 53.5 to 68 m and equipped with a well screen to create an expanded diameter gravel well (EDGW). In keeping with the larger diameter, the volume flux per m screen length was two times higher than conventional 860 mm diameter wells at the site in the subsequent 3 year production period. Although borehole clogging was slower on a volumetric basis and similar when normalized to borehole wall area, rehabilitation of particle clogging at the borehole wall was more challenging due to the thickness of the gravel pack. While jetting the entire borehole wall before backfilling holds promise to remove filter cake and thus limit particle clogging, we found that a second borehole (expanded 4.1-fold to 2460 mm) collapsed during jetting. Overall, the EDGW technique has potential to make the use of deeper unconsolidated aquifers economically (more) feasible, although further understanding of the borehole stability and rehabilitation is required to assess its wider applicability.

Incorporating Snowmelt into Daily Estimates of Recharge Using a State-Space Model of Infiltration

A state-space model (SSM) of infiltration estimates daily groundwater recharge using time-series of groundwater-level altitude and meteorological inputs (liquid precipitation, snowmelt, and evapotranspiration). The model includes diffuse and preferential flow through the unsaturated zone, where preferential flow is a function of liquid precipitation and snowmelt rates and a threshold rate, above which there is direct recharge to the water table. Model parameters are estimated over seasonal periods and the SSM is coupled with the Kalman Filter (KF) to assimilate recent observations (hydraulic head) and meteorological inputs into recharge estimates. The approach can take advantage of real-time hydrologic and meteorological data to deliver real-time recharge estimates. The model is demonstrated on daily observations from two bedrock wells in carbonate aquifers of northwestern New York (USA) between 2013 and 2018. Meteorological inputs for liquid precipitation and snowmelt are compiled from SNODAS (2021). Results for recharge during winter and spring seasons show preferential flow events to the water table from liquid precipitation, snowmelt, or a combination of the two. Recharge estimates summed annually are consistent with previous estimates of recharge reported from groundwater flow and surface-process models. Results from the SSM and KF point to errors in meteorological inputs, such as the snowmelt rate, that are not compatible with hydraulic head observations. Whereas liquid and solid precipitation are measured at discrete stations and extrapolated to 1-km² grid cells, snowmelt is a meteorological modeled outcome that may not represent conditions in the vicinity of monitoring well locations.

Documented Orphaned Oil and Gas Wells Across the United States

Orphaned oil and gas wells are unplugged nonproducing wells with no solvent owner of record to plug and mitigate them, such that the responsibility often falls on government agencies and the general public. Unplugged wells pose risks to the environment, climate, and human health. To develop a national framework to quantify the environmental benefits of plugging and optimize mitigation, we analyze oil and gas well data from state agencies across the United States to estimate the number of documented orphaned wells over time and evaluate their attributes. We find at least 81,857 documented orphaned wells as of September 2021 and 123,318 as of April 2022, representing 2% and 3%, respectively, of all estimated abandoned wells in the United States. We identify at least 20,286 potentially documented orphaned wells as of September 2021 (0.5% of all estimated abandoned wells in the country), of which 8% became documented orphaned wells as of April 2022. We estimate annual methane emissions to average 0.016 ± 0.001 MMt of CH₄ for the 123,318 documented orphaned wells as of April 2022, corresponding to 5-6% of the total methane emissions estimated by the U.S. EPA for all abandoned wells. Although well type (i.e., oil vs gas) is generally available (83% of the 81,857 documented orphaned wells as of September 2021), only 49% and 16% of the wells have information on depth and last production date, respectively. Overall, documented orphaned wells and their attributes, including location, well type, depth, and last production date, require additional characterization and studies to constrain the uncertainties. Nevertheless, our identification and analysis of documented orphaned wells represent the first steps toward characterizing the full set of wells eligible to be plugged and remediated with the federal funding available in the U.S. via the Infrastructure Investment and Jobs Act. Our results can also be useful for the management of the hundreds of thousands, potentially a million, undocumented orphaned wells likely to exist across the nation.