From
1970 to 1984, Didcot ash was disposed of in landfill
at Sutton Courtenay, to where it was transported
by road under a concession granted by the County
Councils. This had to cease as a result of pressure
to make more landfill available for London waste.
However the embargo on disposal by road, a condition
of the planning consent granted in 1964 for the
construction and operation of the power station,
led to the power station operators to seek to
dispose of the surplus ash in gravel pits via
a pipeline. Radley was a convenient choice for
them, being only 8km from the power station with
no intervening obstacles. Conditional planning
permission was granted to the power station operators,
the CEGB, on 17 February 1982 (ref: SUT/RAD/5948)
to dispose of ash in the area designated as comprising
lakes A thru N. (see
map) Under the terms of this consent, Didcot
were required to restore the land to agriculture
and to the original topography. They also needed
approval for specific proposals through each phase
of the operation. In 2005, the current Power Station
Operators, RWE
Npower, submitted such a proposal seeking
approval to fill lakes E and F. When it became
clear that they were seeking significant variations,
some imposed on them by new environmental and
waste disposal regulations, which did not exist
in 1982, and that there was significant public
opposition to the filling of these remaining lakes,
the application for approval was put into abeyance.
However in January 2006, they submitted a brand
new planning application to fill only Lake E (Thrupp
Lake). Despite being granted full planning
permission in early 2007, RWE npower eventually
gave up the idea and, in December 2008, announced
that they would give Thrupp Lake to the community.
In addition,
facilities for the stockpiling up to half a million
tonnes of ash were supposed to have been constructed
at the power station site. This was to enable
meeting fluctuating demands for PFA for
use as a construction material. Unfortunately
this bund (if it ever existed) was lost when Didcot
'B' was constructed and has not been replaced.
Didcot operators therefore have no proper means
of stockpiling ash at the Power Station. This
limits their ability to recycle the ash and requires
on-demand pumping to Radley even perhaps when
conditions there are less than suitable. It is
worth noting that, in 1982, when submitting their
original application, the Power Station operators
considered this stockpile to be essential
to the ash disposal operation.
Since
dry ash is required for some applications, approximately
5000 tonnes of dry ash are also stored in silos
on the site.
The
process of disposal involves pumping a 30% PFA/water
slurry via a specially constructed 440mm pipeline
into the lakes at Radley. The ash is allowed to
settle while the water is drained off through
a gravel filter and series of weirs into the Thames.
Cenospheres
are collected by filter meshes at each weir, harvested
and removed from the site by road.
When
filling is complete and the ash has stabilised,
the area is covered with a sandy overburden (50-85mm)
for restoration to woodland or a thicker (254mm)
overburden plus 153mm of topsoil for restoration
to "agricultural land". Throughout this time,
the land is securely fenced off with no public
access allowed. This is because the filled lakes
are a hazard to the unwary; the surface may appear
solid and safe, especially as moss starts to appear,
when in fact it may conceal dangerous quicksand.
As a result, the lakes are securely fenced off
and remain so for decades.
The
status of the Radley lakes and gravel pits in
2005 was:
- Lakes A-D have been filled and partially restored
to woodland. They however remain fenced off
and there is no public access.
- Lakes H & I have been recently filled,
and are fenced off.
- Lakes G, J & P are in process of being
filled, and are fenced off.
- Lakes E, F, M & N are unfilled and there
is limited public access..
- Lakes K & L are not (fully) excavated
and may remain in their present state.
- Lake P, although outside the area covered
by the original consent, is currently being
filled as part of the lake G/J operations. Planning
consent was given for this in 2003.
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