It took about 30 years for Waipaoa water treatment plant to have its busiest year to date, and that turned out to be this year of extreme weather events.

Built on the outskirts of Gisborne following Cyclone Bola in 1988, the small plant was only ever supposed to be a back-up.

At times it has gone whole years without being used.

But following Cyclone Gabrielle in February, the Waipaoa plant sustained the city for 45 days while urgent repairs were made to the main supply in Waingake.

There hasn’t been much let-up since, with it now producing between one-third and half of the city’s supply on any given day.

It’s no mean feat considering the surrounding environment.

Drawing on the river of the same name, the plant processes brown water which necessitates a dramatic transformation from origin to tap.

“It goes from extremely filthy dirty silt-laden to clean,” Gisborne District Council healthy living team leader Judith Robertson said.

On the windy Thursday Local Democracy Reporting visits, the muddied river has dropped after reaching flood levels of seven metres in the days prior.

The intake tower isn’t working, so the plant is relying on snaking overland pipes to pump water to the nearby plant.

A couple of days later, the water level has dropped enough for the pressure on the intakes to reduce, and the tower kicks back into action.

It’s a challenging environment for Ms Robertson and her team, but she remains positive despite the difficulties.

“It’s been a big test of all its mechanics and process. It’s done really well,” she says. “It was a very well-designed plant.”

On the subject of taste, Ms Robertson doesn’t shy away from the fact that water from the Waipaoa plant won’t win any awards.

The clarity or “turbidity” of the end product also concerns residents at times, and came to the fore last month when a number of people expressed frustration on social media over brown water coming out of their taps.

Ms Robertson says the nature of the Waipaoa River means these challenges are inevitable, but she is confident the water is always safe to drink.

“If there’s a problem on water

. . we’ll be telling the public.  It’s not just our legal responsibility, it’s our social responsibility as well,” she says.

“From the plant perspective, we’re challenged from the source. The source is a big river (that) carries high silt, (and is) very vulnerable to these rain events.

“Sometimes things happen and we remedy (them) as quickly as we can.”

Ms Robertson explains the journey the water takes from the Waipaoa River to the tap — a series of steps which improve its appearance and make it safe to drink.

First it is pumped to settling ponds on the periphery of the plant where the silt is left to settle for anywhere between 12 hours and three days.

The higher the demand in the city (and the less water that can be pulled from Waingake), the less time it can be held in these ponds.

From there it is piped to a clarifier and stirred with its first dose of chemicals, which bind the silt together.

The cleaner water is then carried to a second clarifier where it settles further before passing through a sand filter, and undergoing chlorination and UV disinfection.

Old though the plant may be, its technology is constantly being updated, and Ms Robertson reiterates that the most important aspect is compliance.

In 2019, UV technology was implemented as an extra safety measure to kill bacteria and damage the outer cells of protozoa.

More recently, the council has forked out $60,000 for six compliance meters.

“The cost of doing water is a lot. You can’t not have these things,” Ms Robertson says.

“Every season I’m saying ‘OK, what’s our most critical things, what can you see ageing that’s causing concern?”’

The challenges are ongoing but she is proud of her team and the efforts they put in to make sure the supply is safe to drink around-the-clock.

Issues can present themselves at any time but she’s only ever a call away, whether that be for a vent or an emergency.

“I’m always there if the guys need an ear. I’ll pick up the phone any time of the day or night.

“My headspace is always in keeping the water safe.”