Data release notes : UK Geoenergy Observatories Glasgow Geothermal Energy Research Field Site (GGERFS) ground gas, 2018 and 2019 surveys

In 2014, the British Geological Survey (BGS) and the Natural Environment Research Council (NERC) were tasked with developing new centres for research into the sub-surface environment to aid the responsible development of new low-carbon energy technologies in the United Kingdom (UK) and internationally. Under the United Kingdom Geoenergy Observatories (UKGEOS) project, two sites were chosen, including the Glasgow Geothermal Energy Research Field Site (GGERFS) in the Cuningar Loop-Dalmarnock area in the east of Glasgow (Figure 1). The aims of the GGERFS facility include de-risking technical aspects of mine water geothermal to assess the feasibility of extracting/storing heat energy in an urbanised former coal mine setting (Monaghan 2019; Monaghan et al. 2017; Monaghan et al. 2018). The initial phase of the GGERFS project entails installing a network of boreholes into the superficial deposits and bedrock in the Cuningar Loop-Dalmarnock area of Glasgow to characterise the geological and hydrogeological setting and assess the potential for shallow geothermal energy. The borehole network is also designed for baseline monitoring to assess the environmental status before and during the lifetime of the project. A ground gas baseline is considered important at the GGERFS site to enable us to determine if there are significant ongoing ground gas contributions from sources such as (i) leakage from mine workings/features related to legacy mine workings (ii) gas generated from components of the made ground (building rubble, mine water, other waste) and (iii) natural soil processes. The made ground at Cuningar Loop is known to have been formed from a range of prior land uses (see Ramboll 2018 a, b) and is commonly around 10 m thick. Ground gas measurement is an important tool for monitoring geoenergy sites since sensitive measurements of, for example, CO2, CH4 and associated gases can be made directly within the biosphere in which we live. Monitoring of ground gas in the vadose zone has been undertaken as part of a broader GGERFS environmental monitoring effort that includes groundwater, soil and surface water chemistry, ground movement and seismicity. The intention of ground gas monitoring, indeed the environmental monitoring effort as a whole, is to characterise pre-existing i.e. pre-operational or baseline conditions, particularly with respect to former coal mining, building demolition, waste disposal/landfill, or other industrial activities, before significant development occurs in relation to GGERFS. As such, it should be noted that the August 2018 survey precedes any development of GGERFS and can be considered ‘baseline’ in the conventional sense, whereas the May and October 2019 surveys were conducted alongside site construction but ahead of site operation. Approaches to monitoring ground gas may include long term continuous monitoring using permanently deployed instruments, and discrete surveys involving mobile, wide area screening techniques (for example open path laser, cavity ring down laser) to augment high density grids of detailed point measurements. Point measurement data from ground gas surveys conducted at the Glasgow Geothermal Energy Research Field Site (GGERFS) in August 2018, and May and October 2019 are reported. Ground gas is defined here as: a. gas concentrations in the shallow (c.70-100 cm below ground level) unsaturated zone of the subsurface, and b. gas flux at the soil-atmosphere interface