Wednesday, 13 January 2016

When you scrutinise the actual data...

'Let us quarry right down to your water table', says Aggregate Industries - after all, Amec, its consultants, have been measuring the groundwater at Straitgate for years and should know what's going on.

If that’s the plan, then some scrutiny should be applied to those groundwater figures, the ones that Amec has used to derive this 'maximum' water table - after all, it's people’s drinking water that would be at risk.

Amec has been recording groundwater levels since January 2013 for piezometers PZ01-PZ06, and since September 2013 for PZ07-PZ11. Amec says "The highest groundwater levels on record (20 February 2014) have been hand contoured and are shown in Figure 2.2" 4.2.

But check the actual data, because it's not the same as in Figure 2.2; in fact, the actual data for 20 February 2014 is almost half a metre higher on average than Figure 2.2's "February 2014 (high levels)" - see the workings and data below.

Amec recognises that "the 20 February data... does not necessarily reflect the peak groundwater level at each piezometer" and "has developed an alternative maximum groundwater level grid" such that "when compared with the 20 February 2014 levels, the new maximum water table grid indicated that across the proposed extraction area the water table grids are generally similar and within 1m of each".

In itself, this appears to be an admission by Amec that it cannot predict the maximum water table to any greater accuracy than 1m - reason enough to leave 1m unquarried above the maximum water table

But it gets worse, because the actual maximum groundwater level for each piezometer (data highlighted below in yellow) is over one metre higher on average than the Figure 2.2 data. No surprise that the discrepancies are in AI's favour.

Amec doesn’t have enough data to produce a maximum groundwater contour map with any degree of accuracy. Now it's clear that the data it does have is not being used properly. It's simply astonishing then that AI thinks it should be permitted to quarry right down to Amec's predicted 'maximum groundwater level' - when there are so many people dependent on the site for their drinking water, and when there are so many inaccuracies, inconsistencies, unknowns and anomalies.

But then Amec wrote its hydrogeology reports never really thinking that AI intended to quarry right down to the maximum water table - as all the documents and cross sections illustrate.