Friday, 24 May 2013

Hydrogeology consultants take another look at Straitgate and surroundings

Yesterday, hydrogeology consultants from SLR and AMEC again assessed the streams and springs, originating from and around Straitgate Farm that supply the County Wildlife Sites and peoples' drinking water, in order to better understand the hydrogeology of the site. Over a period of time, flow rates of at least two points in each of the four streams will be spot monitored to assist this task.

AMEC has already had discussions with Aggregate Industries over a number of issues. AI has subsequently decided to leave one metre of sand and gravel over any potential quarry floor - equivalent to a loss of 0.5 million tonnes over the 25 hectare area. AI has also decided to avoid any scheme requiring active dewatering - pumping out water from a void below the water table - for risk of derogating nearby water sources. In addition, the eastern slope of any quarry should be left as a virgin restoration slope rather than any sheer face or infill, again reducing the recoverable deposit but allowing water to recharge the aquifer.

All this does, however, ignore the level of the water table. AI is still optimistically expecting to quarry below the water table during the summer months, when the groundwater level is lower. Water would therefore back up against the eastern slope to form water features at other times of the year, in direct conflict with Exeter Airport, who made it clear, for reasons of birdstrike, that it didn't want any water at all. The events at Heathrow today go some way to explaining why.

Furthermore, as quarrying at Thorn Trees Plantation was not permitted beyond one metre above the water table, it is surprising that AI considers it would be able to do so at Straitgate, where water plays such an important role. It's less surprising, perhaps, when one considers that being restricted to quarrying above the water table would reduce the recoverable resource by over a million tonnes, and therefore throw into question the viability of the complete project.