It has been a while since I’ve read the updates on Silbury, let alone post about them.
Update 27 reports the seasonal shutdown in December/January, and three surface collapses, each up to 1.5m deep. The accompanying photograph is wonderfully captioned ‘ Hill side collapse features’. Archaeological recording will take place prior to backfilling.
Update 28 reports on more bad weather, resultant collapses and tunnel blocking. The ditch flooded (as sight I have yet to enjoy) so the monorail had to be relocated. Skanska and EH are confident that settlement from the Hill void may now be complete.
Update 29 charts backfilling continuance dogged by collapses ‘in the outer sections of the Atkinson tunnel’ related to January’s weather. Backfilling of East/West lateral tunnels completed 8th February 2008. The central Atkinson tunnel is now also filled, as have the Silbury 1 excavated areas: ‘have been filled with a combination of crushed chalk installed by hand and chalk paste which does not include any lime or other materials, thus providing an ncontaminated environment with the aim of ensuring the long term preservation of the central organic material’, good to know. The rest of this update examines the process of backfill into the ‘new’ tunnel, with photographs.
Update 30 reports on void fill completion and removal of Atkinson’s concrete portal (off to the museum with you!) . The entrance is carefully filled with a ‘large bank of chalk’ and then the void behind filled with paste. The total tonnage of chalk used to fill the tunnels is reported in this update, and the confidence that ‘all of the known voids have been infilled as well as practically possible to do with material of the same composition as the original hill construction’. The summit void fill begins (photos).
Update 31 is the latest, and reports on near completion of the summit void, with ‘crushed chalk…hauled to the top of the hill using the monorail’ as the final layer over the pumped chalk. Hill side works have begun - Figures 2 and 3 show a ‘3t 360 excavator’ removing the stacks following the creation of a’stable slope’ to facilitate it, and a dumper bringing chalk up for the infill. Stripping the side of the Hill to create this slope puts the odd evening trespasser into perspective on this SSSI, but I suppose it has to be done somehow. Archaeological recording of the surface craters has taken place.
That’s where we stand. The number of reported collapses during the backfill are a little worrying, but now there’s nowhere for collapsed material to go, and the unstable sections filled from above we can only hope that as her overhaul nears completion she’s now capable of shrugging off any weather the rest of the year may bring.
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