Data release and initial interpretation of test pumping of boreholes at the Glasgow UK Geoenergy Observatory

This report describes a programme of test pumping carried out on ten boreholes at the UK Geoenergy Observatory (Glasgow Observatory), Cuningar Loop in Rutherglen, Greater Glasgow in January and February 2020. It details the types of test undertaken, the datasets generated and how these datasets can best be used dependent on the data analysis being undertaken. Drawdown data for pumping boreholes and observation boreholes is presented in graphical form, together with an initial interpretation of test pumping results. The main objectives of the pumping tests were to obtain data regarding: the physical aquifer properties, in particular transmissivity, of the different hydrogeological zones at the Observatory; to investigate borehole efficiency; and to gather data on the connectivity between different hydrogeological zones. Successful step tests and five hour constant rate tests were carried out in all boreholes except GGB04 in the superficial deposits where a slug test was carried out instead due to the low yield. Time series data of water levels, temperature and conductivity were collected in the pumping and observation boreholes. The constant rate tests were analysed using Jacob’s approximation and Theis recovery methods to give a preliminary interpretation of the transmissivity. The drawdown curves were visually inspected to help identify borehole inefficiency and significant responses from observation boreholes to pumping. Transmissivity values for the superficial deposits are highly variable (0.04 and 225 m2/day), the two bedrock test pumping responses also gave very different results (2.6 and 580 m2/d), three boreholes in the Glasgow Upper mine workings give a consistent transmissivity estimate (950 – 1020 m2/d) and the two boreholes intersecting the Glasgow Main mine workings give transmissivity estimates of 2000 – 2100 m2/d. There is clear connectivity between the bedrock boreholes and the Glasgow Upper mine workings during pumping, with strong responses between boreholes from most pumping tests. There is also clear connectivity within the individual mine workings. There is also evidence of some connectivity between the Glasgow Main mine workings and the Glasgow Upper mine workings. There is an upward vertical hydraulic gradient at the Observatory, with rest water levels approximately 10 – 11 m relative to Ordnance Datum (OD) in the Glasgow Main mine workings; 9 – 10 m OD in the Glasgow Upper mine workings and bedrock boreholes, and 3 – 4.5 m OD in the superficial deposits. Temperature measurements from observation boreholes monitored throughout the testing period show that the groundwater in the deeper Glasgow Main mine workings is warmer than the shallower workings, bedrock or superficial deposits with a value generally 12.4 – 12.8 ºC. Temperatures in the Glasgow Upper mine workings and the overlying bedrock are broadly similar, 11.5 – 12 ºC, apart from GGA04. Specific electrical conductivity measurements from the mine workings and bedrock boreholes lie in the range 1350 - 1600 µScm-1 @25 ºC and are typical of measurements from water boreholes within mined Carboniferous rocks (MacDonald et al. 2017). The conductivity of the superficial deposits is high and variable at 1000 – 1400 µScm-1 @25 ºC, although within the range of those found in Glasgow (Ó Dochartaigh et al. 2018)