OR/19/052 Appendix 3a - Array 1 Borehole descriptions

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Kingdon, A, Fellgett, M W, and Spence, M J. 2019. UKGEOS Cheshire Energy Research Field Site - Science infrastructure. British Geological Survey Internal Report, OR/19/052.
Contributors: Midgley, J, Elsome, J W, Dearden, R A, Chapman, C, Burke, S P, Hough, E, Luckett, R R, and Bianchi, M.
Table 6    Array 1 Summary borehole metadata and planned sampling.
Array 1: Sampling Details
Scientific Objective: Long-term baseline groundwater testing and sensor installation
No of Sites and boreholes per site 9 Sites each with both 1 x 100 m and 1 x 50 m borehole
Expected Lithostratigraphy at TD 50 m boreholes TD in Quaternary, 100 m TD in Sherwood Sandstone Group (Triassic)
Boreholes per site 1 x 100 m, 1 x 50 m boreholes
Likely borehole diameter 13½ nominal diameter
Casing Installed: 50 m boreholes 10¾" permanent steel casing (6–22 mbGL), 150 mm PVC screened between 43 to 49 mbGL
Casing Installed: 100 m boreholes 11¾" permeant steel casing (6–22 mbGL), 150 mm PVC screened between 90 to 99 mbGL
Expected end use Boreholes remain open for future sampling
Samples available during drilling Drill cutting collected sporadically
Cored Boreholes 5 X 100 m cored to sample superficial & Permo-Trias geology
Geophysical logs 5 x 100 m boreholes, Gamma-Ray — Caliper (Borehole diameter)
Geomicrobiology sampling Standard geomicrobiology sampling protocol: 1 sample per 10 m of core in cored boreholes
Gas testing during drilling Equipment
Fluid testing during drilling None planned
Fluid Testing Post Drilling None planned
Pump Testing Long-term Pump testing
Permanently installed equipment Automated & telemetered data logging in 6 boreholes

The array will provide environmental baseline data of the groundwater, ground motion and air quality across the study area. The purpose of the proposed groundwater array is to create a new groundwater monitoring network which will allow researchers to get an improved understanding of the groundwater processes within the Cheshire Energy Field Research Site (CERFS) area. These data will form the natural baseline against which future research activity will be compared.

Borehole components of array 1[edit]

The array consists of 18 boreholes at 9 separate locations in the broad vicinity of the village of Elton in Cheshire. This allows the sampling of the regional groundwater in the vicinity of the CERFS research site and also allows the stratigraphy and variability of the Permo-Triassic geology to be more completely understood.

Following completion of the drilling phase a series of pump tests will be undertaken at each borehole location. In addition these boreholes will also be instrumented with continuously recording sensor to allow the borehole steady-state conditions to be monitored remotely over an extended time interval. Combined with outputs from analytical groundwater geochemistry this will produce a laterally and temporally extensive baseline data set.

Above-ground data acquisition in array 1[edit]

Interferometric synthetic-aperture radar (InSAR) ground motion equipment will also be installed across selected sites at the CERFS area. Equipment will be installed at the surface to continuously monitor deformation or shifts in rock mass in the subsurface. Air quality monitoring installations are included as part of the environmental baseline study for the CERFS area. These are designed by (and will be controlled by) Manchester/York Universities and NCAS1. These installations will include a range of sensors and instruments to monitor atmospheric gases.

Subsurface data acquisition in array 1[edit]

The groundwater monitoring wells within this array allow an environmental baseline for groundwater quality to be produced. The baseline will detail various chemical and physical parameters and general groundwater quality through the collection of groundwater samples and continuous automated monitoring, using data loggers and groundwater quality sondes, over an extended period. The sondes will be purchased, installed and maintained by the UK Geoenergy Observatories capital funding.

The array is also designed to allow pumping tests to be undertaken during the operational phase of the wells. This will help to characterise how the groundwater flows and behaves across the region.

Table 7    Array 1 List of borehole codes and site locations (Cored boreholes in Bold).
Location 100 m BH Cored 50 m BH
SITE A TH0407 TH0420
SITE B TH0101 TH0101 TH0102
SITE C TH0107 TH0107 TH0108
SITE D TH0116 TH0116 TH0117
SITE E TH0122 TH0122 TH0123
SITE F TH0125 TH0125 TH0126
SITE G TH0128 TH0129
SITE K TH0110 TH0111
SITE N TH0104 TH0104 TH0105
Table 8    Array 1 planned hydrogeochemical sampling: summary of intended sample types.
Sample Type Treatment Sample Container Analysis Possible
FA 30 ml Filtered acidified with HNO3 to 1% 30 ml LDPE ICP AES, Na, K, Ca, Mg, SO4, Si, Al, B, Ba, Be, Cd, Co, Cr, Cu, Fetotal, La, Li, Mn, Ni, Mo, Pb, Ptotal, Sc, Sr, V, Y, Zn, Zr, As, Se, ICP MS suite
FUA 60 ml Filtered, unacidified 60ml LDPE Cl, F, Br, I, NO2, NO3, TON, NH4 (SO4, PO4)
FUA 30 ml NH4 30 ml LDPE Ammonium
FUA 30 ml As Arsenic
NPOC Silver filtered, unacidified 14 ml foil capped glass vial Dissolved Organic Carbon
δ18O/δ2H Filtered, unacidified 60 ml HDPE Oxygen and Deuterium
δ13C 100 ml HDPE Carbon Isotopes
Dissolved gases Unfiltered, unacidified Gas Sampling Bomb Dissolved gases
CFCs Small Amber Bottle CFCs
SF6 Clear Glass Bottle SF6
SVOCs 1 x Green Bottle
2 x Glass Vials
NORM 1L Glass Amber Bottle NORMS
Tritium 1L Glass Amber Bottle Tritium (3He)
S Isotopes 250 ml Nalgene Sulphur Isotopes
Radon Daughters Nalgene pots Radon Daughters
Radon 60 ml HDPE Radon (Rn)(Triathler)
Organic micropollutants 2 x 1 L PTFE Lined Bottles GCMS/LCMS
PAHs 1 x 1 L PTFE Lined Bottles PAHs
VOCs 1 x 250 ml plastic bottle Chlorinated hydrocarbons, BTEX
Table 9    Array 1 Non-geochemical sampling (Groundwater Baseline).
Type Data Collection Data Produced/Possible Status
Pumping Tests Step Drawdown Well efficiency, critical pumping rate, optimum pumping rate Operational details to be confirmed
Constant Rate Transmissivity (hence hydraulic conductivity), storage coefficient, aquifer response
Constant Head Transmissivity (hence hydraulic conductivity)
InSAR Ground level monitoring Baseline of ground level stability Confirmed

Special sample handling procedures that will be adopted:

  • One sample will be acidified in the field
  • The majority of samples will be filtered
  • Samples will be refrigerated in the field using ice packs/ice and kept in cold stores over the weekend before shipping to labs
  • There is scope to keep some samples in the cold store for testing at a later date
  • Further parameters need to be further examined including long-term storage requirements