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New modelling tool creates future-proof wastewater network

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Most people probably don’t think about sewerage and storm water systems very much. Out of sight, out of mind. Until they break down.

Now, thanks to sophisticated new computer software modelling technology, SCIRT and Christchurch City Council engineers are making sure Christchurch people get a much better wastewater network. The new system of pumps and pipes running beneath the city streets will be stronger, perform better, and last longer than the old system.

The new technology will also make it far easier for engineers to make changes in the future. And it will save money for ratepayers by ensuring the city’s wastewater system is as efficient and possible. Plant and equipment will be installed where and when it’s most needed.

What’s more, engineers can work out how to do it without even getting their boots dirty.

Senior Planning and Modelling Engineer at the Christchurch City Council, Rahul Raybiswas, has spent about six months working with engineers, planners, and software specialists at SCIRT and the council to develop the modelling tool.

During his time with SCIRT, senior planning engineer and hydraulic modeller Rahul Raybiswas worked with a team of engineers and software specialists to develop a new software modelling tool showing the performance of Christchurch’s wastewater system.

Raybiswas describes it as “the critical tool being used for the comparison of the pre-quake and post-quake level of service of Christchurch’s wastewater network.”

“Level of service” refers to how well the system performs. The software can answer questions like: How will the system stand up to earthquakes and floods? How will it cope as the city keeps growing and more and more people keep flushing toilets, having showers, draining the kitchen sink, and watering the garden?

“What if” scenarios look at what happens if the system gets overloaded. In the worst cases, water could surge out of manhole covers, causing flooding, or sewage could mix with storm water. The model helps show where this might occur and mitigation strategies can be planned to avoid or minimize the impact.

So how does the software modelling tool work? Think of a highly detailed, interactive online map. This map pinpoints main trunk sewers, including new vacuum and pressure systems; overflow pipes, and pumping stations. Minor repairs to damaged sewers and other minor changes don’t need to be included.

The software lets engineers see what effect changes will have – say, putting in a new pump station, or building a new subdivision – will have on the overall performance of the wastewater network, especially flow rates.

To make the software as accurate as possible, flow monitors were installed across Christchurch and precisely calibrated.

The software tool allows for variables such as new infrastructure to plan for the future of the Christchurch wastewater network.

“It was a challenge to keep models current and up-to-date in the face of changes in performance of the wastewater network due to rapidly completed construction projects, and changes in design during construction works,” says Raybiswas.

Different models compare how the network functioned before the earthquakes, how it is functioning now, how it will function assuming there is no more damage, and how it will function after the rebuild is complete. Models have been developed as far into the future as 2041 and 2068.

Raybiswas, who has returned to his role in Council, says developing the tool was not easy. Not all software systems were compatible, so some data had to be entered manually. But he says it has already made a difference. “We helped SCIRT to target work areas we needed to rebuild, where the problems were, where there was more earthquake damage and where more budgeting is required. This is very important information.”   

Published: 21 March 2016