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Refining detailed design of wastewater treatment plant

22 Jun 2009

Refining detailed design of wastewater treatment plant

It's getting down to the nitty gritty as the detailed design of Gisborne city's wastewater treatment plant and industrial separation scheme nears completion.

Project director Peter McConnell reported to council's Wastewater Management Committee this week that the detailed design needed to be finished by early next month in time for tender documents to be released late July or early August.

He said a workshop with CH2M Beca staff in Auckland was extremely valuable as a team of engineers and others went step-by-step through the design and each part of the operational process from pump stations and the treatment plant through to the outfall pump.

"We discussed if we could do things in a different way, and what would happen if something broke. You never get the first-cut design 100 percent correct, so what came out of the workshop was very valuable."

The workshop considered questions such as what would happen in the unlikely event of a total systems failure affecting the outfall pump station. This would be addressed by installing a coupling for hooking up to a mobile pump and bypassing the main pump until it was fixed.

"This approach hopefully eliminates any surprises at the construction and commissioning stages. However, contractors will often look at things from a different angle than the design engineers, and may suggest different options."

Meanwhile, the Registrations of Interest closed this week with 13 companies expressing an interest in the 2 work packages - construction of a new wastewater treatment plant at Banks Street and the separation of industrial wastewater.

"The companies are all very good - all the major players are there, and minor companies are also good and specialists in their field."

The new plant will use a biological trickling filter system to screen and treat Gisborne's wastewater to a higher standard before being discharged through an existing outfall pipe reaching 1.8km out to sea.