Geology and hydrogeology ... …
Report No. SRL/FP/004.1 (10/05/2006)
In addition to the leaching problem of Lakes H/I, evidence is presented to show that the proposed restoration plans for Lakes H/I will lead to removal of volume from the floodplain, both because of the excess of material and because the restored levels proposed are too high to allow rising water from the Thames to cover this area, as it did in 194727. Such levels would also remove connectivity that would otherwise exist between the flood plain and Lakes E&F, thus potentially removing 100,000 cu m of flood plain capacity25. The restoration levels proposed in 2001 should therefore not be approved. Any approval that may already have been tacitly given, should, under the terms of the 1982 Planning Permission29, not be irrevocable, as such plans are, in any case, subject to review at least every two years. To ensure compliance with PPG25, the Environment Agency should be required to approve the final restoration levels and to make a plan to mitigate for any loss of floodplain that they and Oxfordshire County Council may already have irrevocably agreed to.
New evidence, presented in Appendix 1, adds to existing doubt about the quality and the quantity of the Kimmeridge Clay at Radley and its ability to seal the PFA waste, keeping its toxins out of the groundwater. The question whether Lake F will drain (damaging its ecology) if Lake E is drained remains open.
and most importantly, evidence is presented, in Appendix 1, which suggests
example) will have defects in their clay seal if springs Any springs under the clay seal will rapidly erode the its integrity. Springs entering the PFA will prevent
and/or poor quality clay are present. sealing layer and literally undermine consolidation and cause prolonged
instability of the lake contents. New clay bunding, proposed for Lake E, same problems. The Environment Agency should be made aware
will suffer of these
from the risks to
existing and proposed repositories for PFA at Radley. seals can be proven to be good, all PFA filling in the cease and no further filling should be permitted.
Unless the quality of the clay water table at Radley should
The complexities and uncertainties surrounding this issue lead us quite firmly to the conclusion that storage of PFA, or any other form of toxic waste, in landfill within the water table is not worth the risk. Far better, in the case of PFA, to store it, in semi-dry compacted form, above ground where exposure to water is minimal and where there is little hydraulic activity, within the very impermeable compacted PFA, threatening to remove its soluble content into the wider environment. Containment times and leaching rates for such storage should be comparable with, or greater than, bunded wet storage, without the attendant risks.
Oxfordshire County Council, Conditional Planning Permission SUT/RAD/5948 (February 1982) paragraph A.13.
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