We all know that forecasting what a quarry might yield is an inexact business, even if the mineral companies would have us believe otherwise. Perhaps the quote from economist JK Galbraith best describes it:
There are two kinds of forecasters: those who don’t know, and those who don’t know they don’t know.
But how inexact is inexact?
Take Straitgate. Once upon a time, it was thought that the site could yield some 20 million tonnes. In 2012, DCC went out to public consultation telling people that there were 3.6 million tonnes. In 2017, Aggregate Industries will struggle to make the case for 1.2 million tonnes.
When AI eventually came clean on exactly how it hoped to win those 1.2 million tonnes - without retaining a 1 metre unquarried buffer to protect water supplies - the company reminded us that "Calculations have been undertaken by Chartered Geologists".
So let’s look at AI’s other two quarries in the area to see how well its chartered geologists did there.
In 2011, AI reassessed its sand and gravel reserves in Devon and found that it had lost 2 million tonnes; equivalent to a couple of Straitgates.
If anybody can remember as far back as the public meeting in West Hill in the same year, AI explained that 1.2 of those 2 million tonnes had been lost at Venn Ottery (that's what recent application "DCC/3861/2016 Variation to conditions 3 and 19..." was all about), but, to much merriment, the representative couldn’t (or wouldn’t) say where it had lost the other 0.8 million tonnes.
Perhaps it had something to do with nearby Marshbroadmoor? The original planning application gave a figure of 1.1 million tonnes, but, due to geological faulting, nothing like that amount ever came out. After an 'incidental' amount was transported to Hillhead for processing, an application was made in 2010 for the bulk of the reserve, some 176,000 tonnes, to be processed at Blackhill.
Which just goes to show that it doesn't matter how many chartered geologists study the data, AI won't know how much material Straitgate would actually yield up until the excavators did their worst.
This wouldn’t matter to AI if Straitgate still had 20 million tonnes, or even 3.6 million tonnes. But given that it’s now down to 1.2 million tonnes - 900,000 tonnes if the 1 metre is left - the economic benefits of quarrying Straitgate would be marginal at best. AI would therefore be taking a gamble - particularly when its last two sites in the area, two sites with the same geology, have been so disappointing; particularly when Amec tells us that at Straitgate:
Does any of this matter to a planning application? It does when the size of the mineral benefit must be weighed against the destruction of an East Devon farm, the loss of thousands of metres of hedgerows, trees and dormice habitat, the risk to drinking water supplies to more than a hundred people, the risk of birdstrike by creating water bodies 195m directly beneath an international flight path, and the pollution and carbon emissions from a 2.5 million mile haulage plan.
