Professor Brassington – in reply to Wood’s follow-up notes after the meeting with the Environment Agency and others – has produced the following response in relation to Aggregate Industries’ proposal to quarry Straitgate Farm. His report begins:
In my view the most significant aspect of the proposal by Aggregate Industries is the removal of the unsaturated zone over the area of the Straitgate Farm that is proposed to form the new quarry. In my opinion there is no doubt whatsoever that the water which percolates through this area will, once the unsaturated zone has been substantially removed have lost a significant exposure between the percolating water and the surrounding rock. Inevitably, this will mean that the rock/water interactions will have been reduced substantially which in turn can only result in the pH of the percolating waters being reduced and so the acidity of the spring waters will increase.
He also writes:
I fail to see how Wood can come to their conclusion that the recharging water gets through the unsaturated zone in at the most a few days. All my experience of working on the Sherwood Sandstone aquifer has shown that where the rock is poorly cemented and therefore does not have any significant fractures, the rate of downwards flow is a metre or two a year. The references I have read confirm this view that I have discussed in a note dated 17th May 2021 and submitted to Devon CC. A summary of work carried out by numerous authors is given by Ascott et al (2016) that refers to an earlier paper by Chiltern and Foster (1991). The following table from Wang et al (2009) summarizes the general view of the British hydrogeological community on the downwards migration rates including those that apply to the Sherwood Sandstone.
And in summary:
The arguments put forward by Wood do not present a coherent picture of the hydrogeology of the site. They appear not to understand the way that flow through the unsaturated zone works and that the moisture content of the rock defines its hydraulic conductivity. They draw conclusions from the data, such as on the hydraulic conductivity from the leach testing which are not valid as the tests do not provide data and they ignore Aggregate Industries data such as the grain-size analysis that shows that the fine particles in the rock will have a significant impact on reducing the hydraulic conductivity.Wood also misinterprets my statements about the impact of removing the unsaturated zone on the water quality to infer that I am against all quarrying while my arguments relate to this site only. They ignore the published data on flow velocities in the unsaturated zone and without carrying out any tests of their own conclude that the flow rates through the unsaturated zone at Straitgate are very much higher than is possible. They now appear to concede that piston flow takes place although they infer that fracture flow dominates water movement through the unsaturated zone. They interpret the relationship between rainfall events and rises in the water table as supporting their views on groundwater flow that ignore the simpler interpretation of it resulting from piston flow.In my view, Devon CC should not allow a proposal that will significantly reduce the pH of the drinking water supplies for about 100 local residents in the area around the proposed quarry site and I ask them to refuse the application.
