Field-scale evaluation of collection methods for dissolved methane samples in groundwaters

This report presents the findings of a jointly funded project by the British Geological Survey (BGS) and Environment Agency (EA project SC210014) that addresses some of the research needs identified in the EA project SC190007 “Methods for sampling and analysing methane in groundwater: a review of current research and best practice”. Primary field sampling allowed comparison of sample collection techniques for dissolved methane in groundwaters, to provide a field evidence base to help establish good practice guidelines (or protocols). This included evaluation of purging protocols, groundwater sampling devices, surface collection protocols, and the influence of methane concentration. The field study used two boreholes previously shown to have groundwater of contrasting low methane concentration (~1mg/l) ‘Site A’, and high methane concentration (~25 mg/l) ‘Site B’ in close proximity in the Vale of Pickering. The boreholes were previously used for hydrochemical baseline monitoring and were similar in construction and hydrogeological setting, each having shallow (~ 1 m depth) water table and a conventional 3-m long well screen sampling a fractured Kimmeridge Clay unit with methane naturally present from elevated organic matter contents. A stage 1 zero-purge passive sampling device was used to obtain initial samples, followed by a low-flow methodology with parallel use of submersible, bladder and peristaltic pumped samples, with stage 2 sampled after purging a single screen volume, and stage 3 sampled after purging to hydrochemical parameter stabilisation over 5.7 – 7.5 pumped screen volumes. Finally, a post-purge stage 4 sample was obtained with the same passive sampling device. Sample collection protocols tested were open (direct fill vial), semi-closed inverted (submerged-inverted vial), semi-closed upright (submerged-upright vial) and closed (double valve cylinder closed to atmosphere). All samples were obtained in triplicate from each pump during stages 2 and 3, but in stages 1 and 4 only open samples were possible from the passive sampling device. Data interpretation was supported by logged hydrochemical borehole groundwater depth profiles before and after the sampling programme, and by the historical methane baseline record. Methane concentrations measured at Site A are challenging to interpret: they are highly sensitive to purging volume, with a decrease in mean concentration of 72% over the purging stages. This, and the time required to obtain multiple samples, obscured specific sensitivity of methane concentration to pump and sample collection protocol variables at Site A. Although the differences in concentrations seen between pumps and between collection protocol are not statistically significant, the high variability in Site A data overall, 52-117% relative standard deviation (RSD), mean these data are generally not useful for developing good practice proposals. Site B, with high methane concentration, provided more consistent data that allowed meaningful comparisons of methane sensitivity between purging volume, pump type and collection methods with findings that are generally consistent with existing literature. Methane concentrations had a lower sensitivity to purging than at Site A (21% mean concentration declines with ~30 % RSD). Most of the conclusions made from Site B data can reasonably be expected to also apply to sites with lower concentrations. In isolation, pump selection - bladder, submersible or peristaltic pump - makes little difference to sampled methane concentrations. The HydasleeveTM passive sampler consistently produced the lowest concentrations, but is very likely to have sampled different water in the borehole to that sampled mid-screen by the active pumps. However, bladder and peristaltic pump closed samples yield higher concentrations, which is attributed to their capacity to provide increased pressure at low flow, thereby reducing degassing potential. The bladder pump is preferred for this use, due to its lower closed sample concentration variability, which is attributed to the controllability of the bladder pump pressure. The peristaltic pump was tested under favourable shallow water table conditions, and a negative concentration bias that is generally expected from suction pressure was not evident, but this is acknowledged as a concern, especially for deeper water tables, where its use may need more caution. Closed sampling at Site B consistently yielded the highest methane concentrations across all pumps with lowest variability, and is the recommended sample collection protocol. Commercial availability of closed sample analysis is, however, limited. The semi-closed (inverted and upright) methods yielded intermediate concentrations between closed and passive samples, with inverted methods generally giving higher concentrations than semi-closed. When using the inverted protocol, exsolving gas headspace accumulation leads to uncertainties in concentration measurements, meaning that the semi-closed upright protocol is often preferred, especially where degassing is evident or expected although results in this study do not directly support this. Open samples consistently produced the lowest concentrations and should only be used where other protocols are impractical, e.g. sampling from a non-pumped collection device. Switching protocols from open sampling to upright sampling requires minimal investment, and is likely to produce more robust concentration data and/or reduced variability, although results from this study do not provide undisputable evidence of this. The observed sensitivities of measured methane concentrations to different parts of the sampling methodology underline the central importance of using an identical protocol with specific pumps, similar deployments, identical purging volumes or stabilisation criteria, and specific sample collection protocol, in order to generate robust temporal records. Reliable cross comparison of data produced by different organisations requires sampling protocols to be as identical as possible. Any protocol change should be done using an overlap period in which both old and new protocols are used simultaneously, to prevent a sampling-related step change in data. This study also indicates that extended purging of any borehole leads to lower concentration samples over time, which critically has the potential to underestimate methane risk. Combining the findings of this study and wider literature reviewed under EA project SC190007, a concise ‘lookup’ sheet is presented as a non-prescriptive aid to assist practitioners in ‘Groundwater methane sampling protocol development’. It covers: site selection, pump/sampler selection/deployment, supporting reconnaissance measurements, sample collection and protocol, data management and wider use. Finally, outstanding field research needs are indicated. The foremost of these is comparative field testing of down-hole devices for obtaining closed system samples at in-situ groundwater pressure

Environmental Baseline Monitoring Project. Phase II, final report

This report is submitted in compliance with the conditions set out in the grant awarded to the British Geological Survey (BGS), for the period April 2016 – March 2017, to support the jointly-funded project "Science-based environmental baseline monitoring". It presents the results of monitoring and/or measurement and preliminary interpretation of these data to characterise the baseline environmental conditions in the Vale of Pickering, North Yorkshire and for air quality, the Fylde in Lancashire ahead of any shale gas development. The two areas where the monitoring is taking place have seen, during the project, planning applications approved for the exploration for shale gas and hydraulic fracturing. It is widely recognised that there is a need for good environmental baseline data and establishment of effective monitoring protocols ahead of any shale gas/oil development. This monitoring will enable future changes that may occur as a result of industrial activity to be identified and differentiated from other natural and man-made changes that are influencing the baseline. Continued monitoring will then enable any deviations from the baseline, should they occur, to be identified and investigated independently to determine the possible causes, sources and significance to the environment and public health. The absence of such data in the United States has undermined public confidence, led to major controversy and inability to identify and effectively deal with impact/contamination where it has occurred. A key aim of this work is to avoid a similar situation and the independent monitoring being carried out as part of this project provides an opportunity to develop robust environmental baseline for the two study areas and monitoring procedures, and share experience that is applicable to the wider UK situation. This work is internationally unique and comprises an inter-disciplinary researcher-led programme that is developing, testing and implementing monitoring methodologies to enable future environmental changes to be detected at a local scale (individual site) as well as across a wider area, e.g. ‘shale gas play’ where cumulative impacts may be significant. The monitoring includes: water quality (groundwater and surface water), seismicity, ground motion, soil gas, atmospheric composition (greenhouse gases and air quality) and radon in air. Recent scientific and other commissioned studies have highlighted that credible and transparent monitoring is key to gaining public acceptance and providing the evidence base to demonstrate the industry’s impact on the environment and importantly on public health. As a result, BGS and its partners initiated in early 2015, a co-ordinated programme of environmental monitoring in Lancashire that was then extended to the Vale of Pickering in North Yorkshire after the Secretary of State for Energy and Climate Change (BEIS) awarded a grant to the British Geological Survey (BGS). The current duration of the grant award is to 31st March 2018. It has so far enabled baseline environmental monitoring for a period of more than 12 months. With hydraulic fracturing of shale gas likely to take place during late 2017/early 2018, the current funding will allow the environmental monitoring to continue during the transition from baseline to monitoring during shale gas operations. This report presents the monitoring results to April 2017 and a preliminary interpretation. A full interpretation is not presented in this report as monitoring is continuing and it is expected that there will be at least six months of additional baseline data before hydraulic fracturing takes place. This represents up to 50% more data for some components of the montoring, and when included in the analysis will significantly improve the characterisation and interpretation of the baseline. In addition to this report, the BGS web site contains further information on the project, near real-time data for some components of the monitoring and links to other projects outputs, e.g. reports and videos (www.bgs.ac.uk/research/groundwater/shaleGas/monitoring/home.html)

Arsenic occurrence in Malawi groundwater

Despite an estimated 90,000 groundwater points, mostly hand-pumped boreholes, being used for drinking-water supply in Malawi, evaluation of groundwater arsenic has been limited. Here we review the literature and collate archive data on groundwater arsenic occurrence in Malawi; add to these data, by surveying occurrence in handpumped boreholes in susceptible aquifers; and, conclude on risks to water supply. Published literature is sparse with two of the three studies reporting arsenic data in passing, with concentrations below detection limits. The third study of 25 alluvial aquifer boreholes found arsenic mostly at 1-10 μg/l concentration, but with four sites above the World Health Organisation (WHO) 10 μg/l drinking-water guideline, up to 15 μg/l; the study also discerned hydrochemical controls. Archive data from non-governmental organisation (NGO) borehole testing (two datasets) exhibited below detection results. Our surveys in 2014-18 of hand-pumped supplies in alluvial and bedrock aquifers tested 310 groundwater sites (78% alluvial, 22% bedrock) and found below test-kit detection (<10 μg/l) arsenic throughout, except possible traces at two boreholes containing geothermal-groundwater contributions. Our subsequent survey of 15 geothermal groundwater boreholes/springs found four sites with arsenic detected at 4-12 μg/l concentration. These sites displayed the highest temperatures, supporting increased arsenic being related to a geothermal groundwater influence. Our 919 sample dataset overall indicates arsenic in Malawian groundwater appears low, and well within Malawi’s drinking-water standard of 50 μg/l (MS733:2005). Still, however, troublesome concentrations above the WHO drinking-water guideline occur. Continued research is needed to confirm that human-health risks are low; including, increased monitoring of the great many hand-pumped supplies, and assessing hydro-biogeochemical controls on the higher arsenic concentrations found.Keywords: Arsenic; Groundwater quality; Malawi; Drinking wate

Recommendations for environmental baseline monitoring in areas of shale gas development

Environmental monitoring plays a key role in risk assessment and management of industrial operations where there is the potential for the release of contaminants to the environment (i.e. air and water) or for structural damage (i.e. seismicity). The shale-gas industry is one such industry. It is also new to the UK and so specific environmental regulation and other controls have been introduced only recently. Associated with this is a need to carry out monitoring to demonstrate that the management measures to minimise the risk to the environment are being effective. While much of the monitoring required is common to other industries and potentially polluting activities, there are a number of requirements specific to shale gas and to what is a new and undeveloped industry. This report presents recommendations for environmental monitoring associated with shale-gas activities and in particular the monitoring required to inform risk assessment and establish the pre-existing environmental conditions at a site and surrounding area. This baseline monitoring is essential to provide robust data and criteria for detecting any future adverse environmental changes caused by the shale-gas operations. Monitoring is therefore required throughout the lifecycle of a shale gas operation. During this lifecycle, the objectives of the monitoring will change, from baseline characterisation to operational and post-operational monitoring. Monitoring requirements will also change. This report focusses on good practice in baseline monitoring and places it in the context of the longer-term environmental monitoring programme, recognising the need to transition from the baseline condition and to establish criteria for detecting any changes within the regulatory framework. The core suite of environmental monitoring activities currently required to support regulatory compliance, i.e. meet environmental and other permit conditions, encompasses monitoring of seismicity, water quality (groundwater and surface water) and air quality. Recommendations for each of these are included in this report. Additionally, recommendations for a number of other types of environmental monitoring are included – radon in air, soil gas and ground motion (subsidence/uplift). These are not associated directly with regulatory compliance but can provide information to support interpretation of statutory monitoring results. They are also considered important for public reassurance. Health impacts arising from radon and damage caused by ground motion are both issues of public concern in relation to shale gas

Unconsolidated Sediments Overlying Weathered Basement (Map)

Map, Unconsolidated Sediments Overlying Weathered Basemen

Sedimentary Geology (Map)

Map, Sedimentary Geolog

Hydrogeology and Groundwater Quality Atlas of Malawi : Water Resource Area 1: The Upper Shire Catchment

Groundwater in Water Resource Area 1 Upper Shire Basin is interpreted within the same context as presented in the Hydrogeology and Water Quality Atlas Bulletin publication. A general description of the Hydrogeology of Malawi and its various units is provided here to remind the reader of the complexity of groundwater in Malawi and its nomenclature. The various basement geologic units have variable mineralogy, chemistry, and structural history that may be locally important for water quality parameters such as Fluoride, Arsenic and geochemical evolution. Therefore, translation of geologic units to potential hydrostratigraphic units was based on the 1:250,000-scale Geological Map of Malawi compiled by the Geological Survey Department of Malawi (Canon, 1978). Geological units were grouped into three main aquifer groups for simplicity

Aquifer Groups of Malawi and Hot Springs (Map)

Map, Aquifer Groups of Malawi and Hot Springs

Three Aquifer Groups of Malawi (Map)

Map, Three Aquifer Groups of Malaw

Basement Geology and Consolidated Sedimentary Rock (Map)

Map, Basement Geology and Consolidated Sedimentary Roc