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Well what a surprise


SAXON ARTEFACTS were not the only discoveries for contractor Abbey Pynford during piling at a Cambridgeshire site.

The firm is working for Hill Partnerships on a community learning centre and apartments in Huntingdon town centre.

Before piling began, Cambridgeshire County Council's Archaeological Field Unit mapped the site, which has a history dating back to at least the 11th century.

Pottery from the 12th and 13th centuries had been found during a small dig in 1993, so this time a more detailed survey was carried out. This paid off when archaeologists found a complete Saxon earthenware jug.

But even the archaeologists did not know about the hidden well beneath the area being worked.

Abbey Pynford contracts manager Ian Hunter says: 'The archaeologists found the jug and remnants of an old dwelling. But we actually found an old 8ft [2.4m] diameter brickwork well, so we had to do a redesign as there was a pile going through the middle of it.' As the depth of the well was unknown, it decided it would be cheaper to put two piles either side of it rather than bring machinery in to remove the structure and backfill the void.

Hunter says: 'No one knew it was there as it wasn't on any drawings. We were using a standard CFA concrete injection pile and as we withdrew the auger and pumped the concrete in there was a loss of pressure.

'The piling mat caved in over the well and there it was.' The design and build development involves installing about 300 piles varying in diameter from 300mm to 600mm to depths of 12-23m. The piles found in stiff to very stiff Oxford Clay.

Abbey Pynford recently bought a Casagrande B125 and a B135 midrange CFA/bored piling rig and the B125 is piling on the scheme. Before it got to work, the team encountered more recent foundations than the Saxon remnants but these were broken out and backfilled.

The council stipulated that disturbance of the top 600mm layer of the site had to be minimised, 'which of course rendered a conventional system utilising groundbeams effectively redundant', says Hunter.

Instead, Abbey Pynford installed 1,400m 2 of its Housedeck suspended slab system which incorporates a 225mm passively vented void below the structural slab.

The £300,000 scheme is scheduled to finish in early June.

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