Friday 7 June 2019

When AI and its consultants say ‘unlikely’ what does that mean?

In Aggregate Industries' recent planning application for Westleigh Quarry near Burlescombe, to vary the approved working scheme to extract an additional 600,000 tonnes, one of the supporting documents told us what the word "unlikely" means "in reference to the degree of confidence in predicting an impact on ecological interests".

It’s something to bear in mind, when reading documents in support of AI’s application to quarry Straitgate Farm, when consultants say things like:
It is therefore considered that the proposal is unlikely to impact adversely on the quality of groundwater supplying nearby local private water supplies 5.3.44
Or: 

Birdcage Spring is unlikely to be affected by the excavation

Great Fir Spring… is unlikely to be adversely affected by the dry working proposals
Pitfield Spring… is unlikely to be adversely affected by the dry working proposals

In the Westleigh document, it tells us what unlikely means in an Environmental Statement context:
Unlikely: Probability estimated above 5% but less than 50% 2.9
So, let’s rephrase one of those above statements for Straitgate to reflect that:
It is therefore considered that there is up to 50% chance that the proposal will adversely impact the quality of groundwater supplying nearby local private water supplies
Perhaps that might focus minds at County Hall – more so since AI’s legal assurances for alternative water supplies are "unfit for purpose". Consider for example that Birdcage Spring – which has up to 50% chance of being affected by the excavation and supplies a livestock farm – is miles away from any alternative mains water supply.

We are of course assuming that the consultant’s assumptions – unlikely, highly unlikely or otherwise – have not been swayed by its paymasters. It’s something worth pointing out, because when AI’s consultants say "Cadhay Springs are highly unlikely to be affected by the excavation" – i.e. a "probability estimated at less than 5%" – Professor Brassington, an independent expert authority on groundwater, author of scientific papers and textbooks on the subject, paints an entirely different picture:
the reliance of the Cadhay House and associated businesses on the spring for a water supply means that the EA should object to this proposal 5.5 It is strongly suggested here that any proposals to quarry at Straitgate Farm will impact on the fragile groundwater system and cause the flows of springs to decrease and the quality of the water also to deteriorate. 5.7