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Colossal structure begins to take shape

Thursday 20 May 2010, 9:37AM

By Gisborne District Council

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GISBORNE

Gisborne’s new wastewater treatment plant is beginning to make its presence known on the landscape.

The first of about 100 massive pre-cast concrete panels were erected this week to form the walls of the control room building. And within the next six weeks, Gisborne will rival Stonehenge as 32 panels – 8.8m tall and weighing 8.5 tonnes – are placed in a colossal circle to form the exterior wall of the biological trickling filter tank.

The control room building comprises 39 panels, the largest of them 5.7m and weighing about 6 tonnes. Another 21 panels will be erected for the pre-treatment building. Some of these panels facing Banks Street will be embossed with a design used as branding for the wastewater project since its inception.

Unlike the stone used in Britain’s famous standing stones, the panels are made of concrete, pre-cast in Auckland by Preco Ltd.

CH2M Beca environmental engineer Peter Brown said the panels are being trucked to Gisborne, four or six at a time.

“Work is progressing on several of the treatment plant buildings at the same time. The largest pump station – which will hold treated wastewater before it is discharged through the outfall – is close to having its second concrete pour, to finally bring it above ground.”

The completed outfall pump station will be 9.5m deep.

Construction is well under way for the pre-treatment building, where the city’s wastewater will be screened and the solids extracted before being pumped to the top of the biological trickling filter tank for further treatment. Footings are being poured for the base of the 32.5m diameter biological trickling filter tank.

“Two walls for the pre-treatment building are being poured in situ. These will hold the floor on which the screens sit.”

The project’s main contractor HEB Structures has sub-contracted Gisborne’s Currie Construction to build the above-ground structures.

HEB project manager Colin Newbold expected all of the control room walls to be in place within the next few weeks.

“We will start on the walls for the pre-treatment building in two to three weeks and on the biological trickling filter tank walls about late June. We use our 80 metre crane to rotate the panels to the right orientation before they are lifted into position and threaded over the starter bars that protrude from the footings. Temporary steel props hold the panels in place until the roof goes on and ties the structure together.”