²ÝÝ®´«Ã½

Sustainable infrastructure planning: Rethinking scale, timing, and assumptions

Australia was caught off guard by a post-pandemic surge in population growth. Suddenly, wastewater infrastructure built to last decades couldn¡¯t cope. That¡¯s put many of our cities in reactive mode¡ªfixing things after they break because our wastewater planning was based on assumptions that no longer apply.

One of the biggest challenges when it comes to wastewater planning is just how unpredictable the effects of population growth really are. Designing for 5 percent growth is one thing. But if our population grows by 10 to 15 percent¡ªor as much as 20 percent¡ªeverything changes. And it¡¯s not as simple as making pipes bigger.

Let¡¯s consider London¡¯s Victorian-era wastewater system. It was ahead of its time¡ªmassive, brick-lined tunnels you could walk through, Teenage Mutant Ninja Turtle-style. And it was built to accommodate population growth. But over time, it was pushed to its limits: new pipes were added and the system filled higher and higher. Eventually, incoming pipes were submerged. Waste couldn¡¯t enter. Blockages followed. And so did fatbergs.

What started as future-ready wastewater infrastructure became hopelessly out of date. And that¡¯s because its Victorian planners hadn¡¯t accounted for other factors: flow surges, pipe gradients, and material limits. It showed that we can¡¯t build for the future if we¡¯re only thinking about one variable.?

Modelling the maybes: Planning for the future of wastewater infrastructure

Digital modelling has changed the game. It truly helps us plan for unpredictable scenarios that consider a range of different variables.??

In South Australia, our team is busy modelling a whole range of growth scenarios for the state¡¯s water and wastewater infrastructure. We are working with SA Water on the Greater Adelaide Regional Plan project. It¡¯s not about finding one ¡°right¡± plan. It¡¯s about understanding the pressure points and the triggers in each scenario and designing the infrastructure that can respond to each.

The tools we have now are light years ahead of what past engineers could access (the Victorians could only dream of such technology). With digital modelling, we can test thousands of variables, simulate system behaviour, and identify where things are likely to fail. Then we refine and re-run until we get it right.?

Of course, we still need human judgment. This is especially true when the most efficient solution isn¡¯t feasible, cost effective, or acceptable to the community. But we¡¯re better equipped than ever to plan wastewater infrastructure that works in the real world¡ªnow and in the future.

Sometimes, the smartest ideas come from outside traditional housing projects. Take Adelaide Oval. During events at the facility, 55,000 people using the bathrooms was too much for North Adelaide¡¯s existing wastewater network. So, we built a massive storage tank below the stadium¡ªand it¡¯s also below the level of the river Torrens¡ªwhich had its engineering challenges. It holds the wastewater, agitates it to keep it moving, then slowly releases it into the system during non-peak times. This helps to limit stress on the system.

When we proposed a similar solution for a suburban housing project, the response was: ¡°But we¡¯ve never done that before.¡± But we had. And it worked. Stored wastewater reduces the need for larger infrastructure as it levels the peaks.

Building better wastewater treatment infrastructure for growing communities

When we talk about wastewater management, we aren¡¯t just talking about pipes. Wastewater treatment infrastructure is under pressure, too.?

As our population grows, we need to think harder about where and how we process wastewater, especially in areas expected to urbanise quickly. And while no one wants to live near a treatment plant, the fact is this: the closer a wastewater treatment plant is to the community it serves, the more efficient the infrastructure is. There are less pump stations or deep gravity mains. It simply works better.

This is where sustainable infrastructure planning must look beyond traditional solutions. In the UK, our team designed the Clifton Integrated Constructed Wetland¡ªa low-energy system where ponds and plants treat wastewater naturally. No chemicals. No pumps. It¡¯s clean, low-impact, and works well in small communities or edge-of-growth areas.

You still need modelling. Too much flow and the wetland floods. Too little and it dries out. But done right, it¡¯s a treatment system that¡¯s clean, quiet, low carbon¡ªand, perhaps most importantly, doesn¡¯t smell.?

Building sustainable infrastructure for an uncertain future

It¡¯s clear we can¡¯t design and build wastewater infrastructure based on outdated assumptions.

Digital modelling can help us stress-test ideas and plan for a range of possible outcomes. We can also draw inspiration from unexpected places and apply proven solutions in new contexts to solve complex challenges.

There¡¯s no silver bullet for future-proofing wastewater infrastructure. We can¡¯t predict the future¡ªbut we can design for uncertainty. With the right tools and thinking we can build sustainable wastewater infrastructure that¡¯s ready for whatever comes next.