If you thought 1.6m under water was bad, how about 2.8m – in the middle of summer? If Aggregate Industries' model of the groundwater at Straitgate Farm wasn't laughable before, it is now.
Last week we posted how AI’s water problems at Straitgate go from bad to worse. We posted how AI’s quarry plans are now under water in four places. We posted how water levels in piezometers PZ2017/02 and PZ2017/03 have this spring exceeded AI's maximum winter water table model by 1.3m and 1.6m respectively.
But it’s worse than that. Look at this map of the various boreholes drilled at Straitgate before 2011. Look at SG1990/021, south of where PZ2017/03 is located.
This borehole was drilled in 1990. The map refers to "W 6.7", where W is the depth of the saturated zone above marl in metres. What this means is that water was recorded 1.3m from the ground surface (3.1+4.9-6.7). This is clarified in "Report on the reserves of Pebble Beds at Straitgate Farm, near Rockbeare", supplied to us by AI some years ago; a report that was based on analysis of 24 boreholes. The full borehole logs show that on 12/6/90 the water level in borehole 21 was 1.26m below the surface.
But it’s worse than that. Whilst AI’s water consultants Amec (now Wood) have modelled the MWWT – the proposed base to any quarry – to 136m in this location, the data sheet below shows the height of the groundwater here recorded as 138.81m AOD – a full 2.8m above Amec’s guesstimate. Notably, this was recorded in mid June, not in winter or spring when groundwater levels would normally be higher.
Not only does this further undermine Amec’s MWWT model, and any tolerance levels the consultants might produce, but it also means that there is again no winnable sand and gravel from this area or from the – as yet undetermined – surrounding area.
But it’s worse than that. AI was in possession of this data all along, not just in a dusty 1990 report, but on the map above – a map that was also supplied to DCC for preparation of the Devon Minerals Plan. Why therefore has the company proposed to dig in this location? If AI’s water consultants knew about it, why have they proposed the same? Was it just a matter of trying to get away with things?
Because SG1990/021 is exactly where Amec has proposed infiltration areas to control flooding and maintain stream flows; and exactly where Amec has proposed, post restoration, and for evermore:
ephemeral water bodies and species-rich wet grassland to be encouraged in low-lying infiltration areas (in the base of the depressions)
The data for PZ2017/02, PZ2017/03 and now SG1990/021 show however that water bodies in this extended area might not be ephemeral at all – not if these infiltration areas have to cope with surface water run-off from 55 acres, not if there's groundwater sitting here less than 0.5m below the surface. And this is a problem, not only for flooding and stream flows, but also because the MD of Exeter Airport was under the impression that:
For the avoidance of doubt, one of our conditions was that the site will not have any new permanent bodies of water and furthermore we have corresponded with DCC in relation to this matter... if the planning authority approves the application without including the conditions requested by the airport, then the airport has the right to engage the CAA to request that the application be called-in for determination by the Secretary of State.
AI will have to further pull in the extraction boundaries and remodel the MWWT accordingly, which will again reduce the available resource.
