Drilcorp regularly work in the mining and quarrying industry and were recently asked by a local quarry in North Yorkshire to help with an application for a water abstraction Licence. The quarry wanted to abstract 10 3m/hour from a borehole. Their current water supply was from a manmade lake, which had failed to supply enough water needed as the business expanded. The water on site was used for dust suppression and also feeding water to the newly constructed concrete plant. The quarry realised that they needed a new supply and contacted Drilcorp to carry out the full package from application to award of license.
Borehole Engineering Services (BES) work regularly with the Environment Agency (EA) and were required on this occasion to complete a water features survey on the site. A Water features survey involves a visit to site to check for any water courses in a 500m circle from the borehole location. Following our investigations, we found two ground water monitoring boreholes inside the quarry and a manmade lagoon. The findings were sent to the EA and they granted permission to drill a borehole on site along with a pumping test regime on completion.
Drilling:
The borehole was drilled to a depth of 60m through made ground, Limestone, Mudstone and Sandstone with water strikes encountered at 6.9, 26, and 46m
The water bearing strata was screened off with a 1mm slotted PVC screen. The annulus of screen was filled with a dorsilit filter pack. Above the filter screen, a plain casing was installed from the screen to the surface. Installed to the annulus above the gravel pack was a bentonite seal and above this grout injected until it reached the surface forming a sanitary seal, protecting the borehole from surface water contamination.
The borehole was finished at the surface with a 6” PN16 flanged standpipe, 300mm above ground level and covered by a surface manhole.
Test Pumping:
Data loggers were placed in the two monitoring boreholes in the quarry and another installed into the abstraction borehole for background data prior to the pump test starting.
A Subline F14-30 submersible pump was installed to a depth of 50m in the borehole. A flow meter for recording flows was connected at the surface and a pipe led away to a suitable discharge point.
The Pump test was started and due to the water not arriving at its equilibrium state, it was extended from 48 hours to 142 hours.
Water level in the pumping well before the test started was 3.39m below ground level (BGL). During the test it dropped to 9.2m BGL and on completion of the test the water level recovered to within 10% of its starting point within 200 hours, see attached graph of the actual test data.
Quarry abstraction data
Test Pumping:
Data loggers were placed in the two monitoring boreholes in the quarry and another installed into the abstraction borehole for background data prior to the pump test starting.
A Subline F14-30 submersible pump was installed to a depth of 50m in the borehole. A flow meter for recording flows was connected at the surface and a pipe led away to a suitable discharge point.
The Pump test was started and due to the water not arriving at its equilibrium state, it was extended from 48 hours to 142 hours.
Water level in the pumping well before the test started was 3.39m below ground level (BGL). During the test it dropped to 9.2m BGL and on completion of the test the water level recovered to within 10% of its starting point within 200 hours, see attached graph of the actual test data.
Reporting:
Following completion of all the tests, a report was submitted to the EA for approval. The data was passed onto the permitting department of the EA where they reviewed the data and decided as to whether the abstraction licence could be granted on the current data provided. Where groundwater is oversubscribed it is often necessary to reduce the abstraction licence or sometimes refuse the application.
BES carried out the project successfully and were granted a full licence.
