Crikey, everywhere you look you find problems with this planning application.
Aggregate Industries' unorthodox untried unproven seasonal working scheme to quarry Straitgate relies on groundwater levels falling by at least 1 metre during the summer months to allow extraction down to the maximum winter water table – the MWWT. Aggregate Industries’ Regulation 22 document claims:
2.2.8 By working only to the MWWT then during the summer months the water table will be lower. Therefore across the areas being worked the zone of water level fluctuation is undisturbed. This zone is at least 1m thick. Appendix C includes a plot showing the contours of average summer unsaturated mineral thickness, derived from the MWWT (i.e. the final proposed depth of working) and the Average Summer Low Water Table from piezometer readings.
There’s one big mistake right there. Because contours of "average summer unsaturated mineral thickness" will not be generated by using average summer lows. That only shows – in Aggregate Industries' favour of course – the average summer maximum unsaturated thickness. Those dependent on drinking water from the site should instead be concerned about the minimum unsaturated thickness below the MWWT in summer, which can only be derived using maximum summer groundwater levels. You can guess why Aggregate Industries didn’t do that.
In fact, only by using maximum summer groundwater levels would the ability to reliably comply with planning conditions be demonstrated, knowing that groundwater levels can rise by up to "1m in 5 days", and given that the Environment Agency states:
our recommended condition requires that the base of the excavation is no closer to groundwater level than 1m at any time.
But this post is about more than that.
We have in the past pointed out that AI's seasonal working scheme for Straitgate can't work as described, that groundwater levels do not fall by 1m around the piezometer location PZ05, a fact that Aggregate Industries recently tried to bury. Groundwater levels do not fall by more than 1m at PZ01 either, but the company argues that at the extraction boundary this would conveniently increase to 1.17m. It’s an absurd claim; Aggregate Industries can’t make predictions to the nearest metre, let alone the nearest centimetre.
But now, lo and behold, another location has come to light where Aggregate Industries’ seasonal working scheme can’t work.
The Environment Agency, after a protracted struggle – both by Professor Brassington and us, posted here, here and here – finally accepted that groundwater levels recorded in 1990 should, together with other borehole data, be used to define the MWWT. This was reflected in the Environment Agency’s revised conditions and Position Statement which reads:
Based on further information received from SAG we recommended to Devon County Council that the applicant updates the Maximum Winter Water Table grid with groundwater levels recorded at the site in 1990.
Aggregate Industries’ consultants subsequently produced a revised MWWT to accommodate groundwater levels recorded in borehole SG21/90 (also known as SG1990/021).
But crucially, those 1990 groundwater levels were recorded in summer. The MWWT at location SG21/90 therefore now reflects a summer level. The MWWT and the summer level at SG21/90 are one and the same; the difference is ZERO. Clearly, groundwater levels do not fall by 1m from the MWWT here in the summer. Only by adding 1m to the MWWT in this area could Aggregate Industries' seasonal scheme even begin to work as described.
Appendix C – referred to above, shown below – and its Himalayan-style contours "of average summer unsaturated mineral thickness" is one of the documents Aggregate Industries is relying upon for its planning application.
We have already posted that it contains errors the height of houses. That was before the Environment Agency recommended the MWWT be updated using 1990 data. What that means is that around SG21/90 there is not 4m of summer unsaturated thickness as shown above, and here, there is in fact ZERO.
Given that those lines of fiction were interpolated, this figure will obviously have a knock-on effect on the surrounding area, and on the amount of resource available. Obviously, extraction down to the MWWT would never be possible – if planning conditions were complied with – in areas where the groundwater does not fall by 1m in summer.
Lines of fiction? Not only were those amazing patterns derived from just a handful of data points, but in some areas those claimed "contours of average summer unsaturated mineral thickness" even exceed the depth of mineral between the MWWT and underlying mudstone. Sense-checking is not Aggregate Industries' strongest suit.
But it doesn’t stop there, because those Himalayan contours above were generated in July 2017. At that time, only 8 piezometers had been recording groundwater levels for longer than 12 months. The above contours have therefore NOT been updated by the summer groundwater levels recorded over the almost 4 years since then – not just from those 8 piezometers, but also from piezometers PZ2017/01, PZ2017/02, PZ2017/03, PZ2017/04 and PZ2017/05 installed in 2017.
Neither have those contours been updated using the summer 1990 levels.
Without using ALL the available summer groundwater data for the site, without using maximum summer groundwater levels, no-one can know what might be revealed, no-one can make an informed decision.
As things stand, therefore, the Environment Agency's condition could not be met: there would not always be 1m or more of unsaturated material below the level where Aggregate Industries would be working. It's yet another fail.
