Here’s one produced by Sage last year.
Even though the four groups were all looking at the same pandemic, there was a range of projections.
However, the chart came with a warning:
Note: All models have uncertainty / margin of error
Which is to be expected when you have limited data. Any expert knows that.
Any expert except the ones working for Aggregate Industries, who have for years failed to answer the simple question: How accurate is your model of the Maximum Winter Water Table – when it has been guesstimated with just 6 numbers?
As we said in this post last year, AI still won’t come clean on accuracy of MWWT:
The MWWT – the maximum winter water table – would be the base elevation of any quarry at Straitgate Farm. It is a model, a prediction of what might be happening across some 55 acres, based on water levels recorded in just 6 piezometers. The accuracy of this prediction would matter less if Aggregate Industries were planning to leave a safety margin, an unquarried buffer, above this surface – but it is not.
Aggregate Industries’ consultants, Amec Foster Wheeler now Wood*, clearly needed the help of a dictionary to understand tolerance. As we posted:
All AFW was attempting to do was to obfuscate, to confuse, to muddle the EA. All AFW was doing was showing the difference between how two techniques (kriging and radial basis) have interpolated 6 measurements to predict groundwater levels across 55 sloping acres. All AFW was showing was the difference between one inaccurate model and another inaccurate model. This is not a tolerance, it is a difference. What AFW has NOT done, for very obvious reasons, is to consider – at least in public, for the benefit of locals, the Council and the EA alike – the inherent inaccuracies of each of those techniques.
But muddle the Environment Agency it did. The Agency clearly didn’t grasp that all models have uncertainty / margin of error and subsequently wrote in an email in June 2018:
We have reviewed the document and we are satisfied that it answers our questions about the derivation of the Maximum Winter Water Table grid.
However, some experts do get it. Professor Brassington warned:
The MWWT for this site has been defined by using a computer model as the number of piezometers (six) are insufficient to cover the quarry area in sufficient detail. Computer models of groundwater systems are good at showing changes in groundwater levels although they are poor at showing the actual amount of such changes. As a result, the computer model derived MWWT surface is unlikely to provide an accurate representation of the real maximum groundwater levels...
I am concerned that there is a very steep hydraulic gradient across the site, from around 152m in the west to less than 135 m in the east, and the limited number of piezometers used to grid the water table surface. Variations in the shape of the water table cannot be contoured based on the number of piezometers used in the application... The steep hydraulic gradient combined with limited monitoring, in my opinion, is likely to result in errors in the actual depth to maximum groundwater across the site.
Prof Brassington was sufficiently concerned to recommend:
an unquarried buffer of at least 3 m is left above the maximum water table to minimise the negative impacts.
It's all a matter of which experts Devon County Council should trust: consultants who whitewash reports to help clients win as much material as possible, or an award-winning Professor who has made "an outstanding contribution to hydrogeology." Tough call.
* In other news, Aggregate Industries' water consultants Wood have sets aside an extra $151 million to settle corruption and bribery probes at Amec Foster Wheeler, reports the FT. The Serious Fraud Office launched an investigation into Amec Foster Wheeler in 2017, as we posted at the time.
Wood sets aside extra $151m to settle corruption probes https://t.co/jBOpol0roY
— FT Energy (@ftenergy) March 16, 2021
