The Civil Engineering Contractor October 2018 | Page 21

ON SITE The tight construction site abuts the surrounding buildings. Liviero Building, says: “The civils component of the building [currently under way at the time of interview] is a relatively small portion of the total cost, having but one basement level. As there had been a pre-existing basement — of approximately two floors of retail and a basement, which was demolished — no sewerage work was required.” Liviero Building is the main contractor, with much of the work subcontracted to civil construction and building development company Harrowgate. The latter specialises in earthworks, road and township infrastructure, substation civil infrastructure and building works, including warehouse construction, and more. The construction of the entire building will, over the course of the project, involve 11 000m 3 of concrete and 1 600 tonnes of steel. At the time of the site visit, the basement floor had just been completed and work had commenced on the basement surface bed. Approximately half the ground floor slabs as well as much of the ground beams and basement columns were already completed, including the power caps and the foundation brickwork. “We recently started work on the ground floor columns as well,” says Van Dalen. Liviero Building will also be responsible for the rest of the 17-floor building. Challenges The pre-existing basement structure complicated the earthworks, explains Hardus Marx, site quantity surveyor for Liviero Building. “It made the earthworks more difficult because we did not have a clear idea of what was below the ground. The only way to see conditions below ground was to dig down and see for ourselves. In the event, we found a lot more concrete than initially expected — including bits of broken piles. Consequently, we had to remove 8 000m 3 of material more than had been budgeted.” There were a number of other surprises too. “There was a little bit of asbestos found in the basement structure, while beneath the ground we unexpectedly found clay. An entire process — including a legal process with specialist permits — was required to remove the asbestos before our subcontractor Dracon Demolitions could start with this asbestos removal task. They in turn subcontracted it to a specialist firm. There was no rock found on site, but the clay found in the soil meant that conditions were far from ideal when it came to compacting the earth. “We had to drive in 366 precast piles, and poor soil conditions meant that we had to import close to 1 200m 3 of G7 aggregate alone, to create a suitable foundation for piles, in addition to an amount of dump rock to make different layers, followed by the geotechnical membrane,” CEC October 2018 - 19