Even in areas such as near the Thames. You need to bear in mind that the th e surrounding geology is alluvial deposits, over Terrace Gravels and then t he London Clay. Water within the terrace gravels is in continuity with the Thames, so with the recent rainfall the levels will be high, if not overflo wing. The water level within the Chalk aquifer is at a much lower level and is sealed from the aquifer in the terrace gravels by means of impermeable geology, namely the London Clay, Woolwich and Reading Beds and Thanet Sands . The two aquifers are therefore at different levels and not in direct cont inuity. It would therefore be possible to discharge into the chalk aquifer with the Environment Agency's permission.