No 1 bore at Kai Iwi is one of three drawing water from the huge Nukumaru aquifer. There's plenty of it but it's hard, very hard. Photo / Bevan Conley
No 1 bore at Kai Iwi is one of three drawing water from the huge Nukumaru aquifer. There's plenty of it but it's hard, very hard. Photo / Bevan Conley
If you're charged with delivering the most precious commodity to your community, then you have to make sure that water is getting there all day, every day.
Obviously, getting water to a broad range of users 24/7, carries a major cost.
In pure accounting terms the city's water infrastructure –that's the bores, the pumps, reservoirs and myriad kilometres of underground pipes – have a current book value of just over $79 million. Replacement costs are estimated at $153.5m. This makes something most of us take for granted a big ticket item.
Whanganui has the usual mix of households, commercial enterprise and major industrial operations and all need water.
But given the city's age - and remembering it was once one of the country's biggest settlements - it means there is a significant sprawl of underground pipework that is well beyond its "use by" date. Some of the stuff is up to 100 years old and big chunks of it are 60 years old or more.
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Those pumps, especially those from the main supply at Kai Iwi, use a lot of electricity, something like $55,000 a month.
Senior engineering officer Dave Rudolph, the man in charge of water services, says council tries to mitigate those costs by running the pumps in off-peak times. But even with that sort of housekeeping power charges to run the city's entire water supply network is around $1m a year.
Rudolph says the three reservoirs on Great North Rd would cost about $12m each to replace. Setting up one complete and operational bore site costs around $1.5m. That trio of pumps at Kai Iwi are worth about $60,000 each.
And maintaining the supply is on-going. Major work has just been finished on the city's oldest reservoir at Westmere, with a new roof and internal strengthening for the facility which is about 100 years old.
Those three reservoirs hold about 23 million cubic metres of water each and Rudolph says that's enough to handle the city's demands.
"It's more a matter of sourcing water," he said.
To bolster supply, council is in the throes of commissioning a new bore near the Kai Iwi rail overbridge on State Highway 3.
And council has been renewing the main pipelines coming from Kai Iwi to the city. That project started 10 years ago with the last 3km tackled over the next three years.
"There are some high-risk areas along that route because it runs along the state highway corridor. You're also dealing with very high pressures in those pipelines," Rudolph says.
Of the hundreds of kilometres of water pipes criss-crossing the city underground, much of it is old and subsequently needs to be replaced.
This isn't an uncommon sight when work is carried out on Whanganui's ageing water pipes. Photo / Bevan Conley
Rudolph says the city gets a clean bill of health for its water supply, but running it through aged pipes "is a bit like drinking water out of an old gumboot".
There's a lot of spiral-riveted and spiral-welded pipe as well as cast iron pipes carrying water around the city, some of it anywhere from 60 to 100 years old.
He says they know what pipework is in the ground and council has developed what it calls a criticality programme, identifying what needs to be replaced and when that can happen. While that depends on annual budgets, it's a programme that can be affected with unforeseen events such as leaks or a mains rupturing.
"We try to do the most critical ones as soon as we can but it's dictated to by how much money is in the budget."
Rudolph said council has been working a renewal/replacement model for about three years and he hopes to have all the spiral-riveted pipes replaced within the next few years.
Remember the key word is "critical"; the worst comes first.
"I'd hope within the next five to 10 years we'd have a significant amount of those critical assets done. The mains that are critical to our supply will have priority while those smaller pipes, say down to 32mm, could be pushed back."
He says an impediment to some of the work has been slow growth in Whanganui. However, things are happening.
"There is a rise in developments around the city, and industrial zones like Mill Rd in Castlecliff, is seeing significant growth, so we have plans for that. The hardest part for us is trying to find contractors to do the work because everyone is busy."
