The Lowry Centre site, protruding into the Manchester Ship Canal and located on Salford Quays' onetime pier 8 grain wharf, created early challenges for foundations subcontractor Kvrner Cementation.
The centre's roughly triangular footprint is bounded by 18m deep diaphragm walling now exposed and incorporated into the structure as basement walls. Everything inside the triangle sits on some 800 continuous flight augered concrete piles, bored up to 22m into bunter sandstone bedrock.
Each pile was sunk from the pier's original ground level and its upper 4m length later exposed as the basement area was excavated around it. The pile's top section was then cut off and pile caps formed at basement level to support the various structures above.
Tight 75mm pile positioning tolerances, and an equally severe verticality requirement, related not only to each pile's original ground location but equally to the 4m deep level when the upper section was exposed and removed. Achieving the required piling accuracy was hindered by uncharted underground obstructions including timber wharfing, warehouse foundations and even debris from the old bed of the River Irwell underlying the site before excavation of the Manchester Ship Canal in 1894.
Most of the 70 or so piles that ended up slightly out of alignment could still be accommodated by a revised pile cap design, but some 20 others needed a second attempt.
The resulting 'couple of weeks' delay has yet to be recovered. But Bovis project director Peter Roberts is optimistic time can be saved during the finishes stage to allow structural completion on schedule, just weeks before the start of the next millennium.