Linhay Hill Quarry in the Devonian Chercombe Bridge Limestone at Ashburton, Devon, is a limestone quarry which supplies a range of aggregates, ready mix concretes, asphalt, blocks, paving, sand and lime, for new roads and highways maintenance, building construction and agricultural use across Devon.

It is planned to extend the existing quarry to the east so that it can continue to function for a further 40 years or more. To do so requires an improvement in understanding of the hydrogeological regime in the vicinity of the quarry, in particular to understand how surface water runoff drains to groundwater via sinkholes in the limestone, and whether this drainage impacts inflows to the quarry itself.

To the north and north-east of the existing quarry, springs to the north of Alston Farm and surface runoff from Alston Wood and surrounding farmland flow toward the south-east across farmland, eventually draining to a sinkhole within an artificial drainage ditch. Flow entering this sinkhole is thought to potentially contribute to flow from a karstically-enlarged fissure intercepted by the quarry wall. An alternative flowpath for water entering the sinkhole is to drain more directly to the south and east, potentially discharging as baseflow to the the Kester Brook, a tributary of the River Lemon. To improve understanding of this system EGG Consultants Ltd will conduct a ‘Tracer Test’ in order to partially quantify groundwater flow entering the sinkhole and monitoring for tracer arrival at a number of locations potentially receiving flow from the sinkhole. Background hydrochemistry of numerous springs, streams and sinking waters forms part of the background study to characterise natural variability in geochemical parameters for understanding groundwater flow patterns.

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