THE SOLAR Pyramid's three monumental towers lean towards an apex 45 m above ground level.
They won't meet, but will create the illusion of a pyramidal structure.
The tallest of the towers will lean at an angle of 55 degrees.
The Pyramid was originally intended to be 30 m high, but has grown to 45 m to create a more dramatic effect. Its blades are 11 m wide.
'This thing has grown and grown, ' says Mr Morton.'And the foundations have changed with it.We started off with tension piles with rock sockets.We've now moved to cantilage.'
The Pyramid consists of three highly unstable structures.'The centre of gravity is nowhere near the footprint.We have the danger not only that the structure could overturn, but also of torsion - the towers could twist around the fulcrum.We've got some tough loading conditions, 'Mr Morton says.
Because the Pyramid will be constructed on poor ground - 24 m of colliery waste over coal measure - the piles need to be particularly deep.
Geotechnical contractor Van Elle has carried out site investigation works.
'We had to ignore the colliery waste in the designs.We expect the structure will need up to fifty 25 m-long steel tubular piles.They could be raking piles (driven diagonally), but that's to be determined, ' says Andrew Johnston, managing director of Van Elle's geotechnical division.
Neil Robertson, business development manager for Scott Wilson Kirkpatrick's central region, says building on made ground could cause problems.
'The shadow has to fall in exactly the right place, and the piazza will take very little differential settlement.Tolerances for the structure will be low - possibly 15 mm.And there will be quite significant loads from the sails in terms of wind loading.'
Marshalls is supplying 3,000 sq m of its detailing blocks, branded Stein + Design, for the piazza at the base of the pyramid.As well as acting as the pavement, the multi-coloured block system will be used to delineate the complex equation of time at the base of the Pyramid.
'This is going to be a big challenge for us, ' says a spokeswoman for Marshalls.'We'll be using our in-house CAD team for the design.'