Source: Whangarei District Council
Updated: 24/07/2020 1:53 p.m.
The new $30 million water treatment plant due to open in Whau Valley early next year will be able to turn brown, silty, dam water into pure drinking water much faster during major storms than the current plant.
“As rain and floodwaters rush down from the hills into the dam they bring all sorts of sediment and debris with them, churning up the dam and turning the water brown and opaque. Water in that condition is more difficult to process than the usual, fairly clear, water taken from the dam,’ says Council’s Water Services Manager Andrew Venmore.
“During last weekend’s storm, the Whau Valley plant had to stop for 24 hours while staff adjusted the treatment process to deal with the highly turbid water. Floods also swept through one of our outlying treatment plants, taking it out of action for four days. In addition, landslides caused two water pipeline bursts in the Onerahi area.”
Mr Venmore says these three factors meant clean water stocks in reservoirs got dangerously low following the extreme rainfall event. Some reservoirs had got below 20% by the time the Whau Valley plant was restarted late Saturday night.
“Our District’s residents developed good water saving skills during the big dry of the past few months, and as soon as we asked them to save water, they took action. Their efforts help to maintain reservoir levels between 20 and 30% until the Poroti plant was up and running again on Tuesday night. Since then the reservoirs have been slowly filling towards normal levels of over 80%.”
“In usual conditions the existing plant can process 15,000 cubic metres of water a day – although this was reduced during this storm – but the new plant is designed to process 22,000 cubic metres a day and handle poorer quality water.”
Mr Venmore said all three of Whangārei’s Water Treatment Plants are now back in operation following the storm.
While work on the new plant was not affected by the storm, the same cannot be said for many of Council’s other assets.
Storm causes delays to Porowini Ave bridge opening
“We are all very disappointed to see the Porowini Ave bridge, due to open next week, put back a month by flood damage,” says Council’s Chief Executive Rob Forlong. “The team had only a couple more days of work to complete the job, but the flood has ripped through, torn down the scaffolding and broken a sewer pipe. The team has been pulling the scaffolding out of the river, reassembling it, repairing the pipe, and has yet to check what, if any, damage has been done to the structure.”
Widespread damage to District’s roads
As of yesterday, ten roads remained closed around our District, seven due to slips, two to flooding and one due to an unsafe bridge. One of the worst affected roads is Matapouri Rd, where there are 16 slips to clear in one section between Kaiatea Rd to Sandy Bay. This work is expected to take around 2 weeks. A further 32 roads are still down to one lane and people should drive with caution.
“At the moment our priority is on getting our closed roads open, so we are asking residents to be patient if their roads has not been fully cleared yet. We will get there but we are working on the most urgent roads where residents have no access to their properties and will prioritise other roads,” said Mr Forlong.