The City of Darwin’s Assets Manager, Nadine Doulas will outline the challenge of managing the city’s stormwater assets at the IPWEA National Conference when it heads to her home turf in August. We quizzed her about that particular challenge, plus other aspects of managing Darwin’s assets.
You refer to Darwin’s underground stormwater assets as “the big unknown”. Can you elaborate?
Our 350km of relatively young underground pipes, culverts and pits were mostly built in the 1970s, which means they’ve been largely left to their own devices, with occasional reactive maintenance when needed.
So the system is “unknown” in the sense that there’s been no significant replacement work and we‘re not entirely sure which assets might exceed their “expected” life of 80 years, and which might fall short in some way.
But what we do know is that the population of Darwin has almost quadrupled since the 1970s and that the underground infrastructure needs to support ever increasing development.
What are you doing to address that?
Well, up until a few years ago most pipes were still only in the first half of their life so we felt confident that repairs and maintenance could be done only when road or ground surfaces were showing signs of failure, rather than conducting too much internal inspection.
But more recently we’ve used CCTV to inspect larger areas of the stormwater network to get a better overview of the state of the asset.
We’ve found CCTV incredibly useful in pinpointing areas of failure.
But even once we’ve pinpointed defects, the “unknown” factor still remains when it comes to deciding whether to just monitor them, repair them or replace them.
Why is that a problem?
Well, even though best practice might suggest immediate repairs are necessary, the fact is that some defects have probably been there for years, and will remain there for many more years, with little impact on anything around them. So the key is to determine how critical a defect is in terms of the impetus to get it fixed in cost/benefit terms. Certainly, the use of CCTV helps us in making more accurate decisions about what to prioritise.
Another factor to consider in a fast-growing city like Darwin is whether to upgrade the diameter of pipes. For instance, if a 1 metre pipe does need serious repair or replacement, should it be replaced with a 2 metre pipe to cater for development or infill in future years? That sort of decision is important, because replacing a pipe when you have easy access is far better than trying to do so after development or infill has occurred.
What other challenges do you face as an asset manager at the top end?
The wet season is certainly one! It runs for about seven months, from October to April, and it really slows up construction, maintenance and repair work.
So our main window of opportunity is the five month dry season. But the first two months of that coincide with the usual run-up to the end of the financial year, so we often don’t know what’s in the budget until long after the rain has stopped.
Another challenge we face is that the wet season doesn’t make Darwin a great place for contractors to operate. The rainy period means they can’t be assured of steady work throughout the year. So we don’t have that many of them up here. And those that are here are pretty tied up right now on the huge INPEX LNG project.
Consequently contractor costs are high and there’s very little consistency when it comes to knowing their availability, let alone their pricing, which can vary quite a lot from job to job. So that means you might spend quite some time planning a project without knowing that all-important variable of cost until the very last minute.
So what’s your final word?
Okay, to sum it up, asset management wouldn’t be the stimulating profession it is without the challenges. I don’t know of any asset manager who feels they have enough funds to do everything they want to do. But we need to do what we can with what we have at the time. In some years that might involve just maintenance, and in other years renewal, but the important thing is to plan for the long term. I also think asset managers need to interact with one another and swap ideas as much as possible. That’s one reason I’m really looking forward to the National Conference up here in Darwin.