Permeability Testing Study
Client: BAM Ritchies
Location: Lower Thames Crossing, Grays. Essex
Duration: November - December 2020
Stuart Wells undertook a series of constant head permeability tests in accordance with BS EN ISO 22282-2:2012 as part of the Lower Thames Crossing Project.
As part of the testing, the drilling contractor drilled the wells open-hole to defined depth. A temporary 50mm uPVC borehole liner was installed encompassing a slotted section with a gravel filter pack.
50mm and 75mm surface water pump and associated hoses where used on site and a short equipment test undertaken to establish outline flow and response conditions.
Constant Head Testing was then undertaken with water pumped into the borehole. This comprised of 3no x 90 minute step tests were a steady water level was maintained in the borehole. Upon completion of each step the pumping flow rate was increased to maintain a higher steady water level. Upon completion of the final step test, pumping was stopped and the falling head ‘recovery’ response was observed.
Total injected water volume and inflow rate, for each step was measured using 2no x propeller flowmeters.
Water level within the borehole was measured manually using a dipmeter and Solinst datalogger.
In undertaking these tests in accordance with BS EN ISO 22282-2: 2012 Stuart Wells were able to provide the client with accurate permeability values for each well to aid design. A full factual report was produced and submitted to the client.