Quarry Resource Estimation
The Land Consultancy Ltd (TLC) was commissioned to undertake a preaquisition borehole and geophysics survey of a large disused clay and sand and gravel quarry site near to Doncaster. The sand, gravel and clay drift deposits were of Glacial origin; the water bearing sand and gravel deposits overlay the clay soils at depths of approximately 5m.
The main interest in the site was determining the volume and suitability of the clay present which had historically been extracted from the quarry and utilised to form low permeability capping layers to landfills.
The investigation confirmed that on the clay was suitable for use in landfill capping layers and that a large volume of clay remained. However, as the clay had a high shrink/swell potential care TLC advised that would be needed during placement in hot/dry or wet weather, so as to avoid bogging down of plant and to ensure that the highest possible dry densities are achieved.
In addition, the borehole and geophysics evidence suggested that the suitable Glacial Clay occured within distinct zones and that the geology can change abruptly both laterally across the site and with depth. Therefore, it was advised that:
•tight quality controls should be put in place to minimise the risk of the receiving landfill rejecting any excavated clays; and,
•site investigation works and laboratory testing of the clay should take place prior to its excavation to ensure suitability.