Flood relief in the pipeline on Waiheke Island
Improvements are planned on an Auckland Council site blamed for floods that caused millions of dollars of damage on Waiheke Island.
Plans are being drafted to create a five metre wide open drain down the side of the Waiheke Island refuse transfer station in Ostend, council's Healthy Waters strategy team manager Claudia Hellberg said.
A steering group of council staff, business owners and local board members was formed after severe flooding hit about 35 businesses in Tahi Road, Ostend, in March and April.
The group supports the plan for a new culvert along the Tahi Road side of the transfer station site.
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Hellberg's rough estimate of the cost of the new drains is $3 million.
Jesse Ball had to close his water delivery and bottled water companies on Tahi Road after heavy rain caused flooding to his businesses and partially submerged trucks in March.
Ball said the council had blocked the natural flow of stormwater on Tahi Road by failing to install adequate drainage at the transfer station site.
"It's currently a dam. The fact the council has acknowledged that and is willing to fix it is a win," he said.
His businesses, Only Water, Waiheke Water and Waiheke Imperial, are fully insured for damage that will cost more than $3 million to repair.
Ball hopes to open again in November so his companies can provide water deliveries that are essential for the island community during dry summer months.
Another Tahi Road business, Cito Holdings, has been battling to gain resource consent from the council for clean fill it used to raise the level of its site, so it escaped damage in the March floods.
Waiheke architect Ron Stevenson, who has been acting as a consultant for Cito Holdings, said the lack of drainage at the transfer station caused flooding a metre deep on the Cito property in 2011, soon after the transfer station was built.
The 2011 floods destroyed vehicles, equipment and materials at Cito and other businesses.
"Council have caused this flooding and they have been warned that this would happen again," he said after the March floods.
Hellberg said the new open drains will replace pipes that are too small to get rid of stormwater during heavy rain, particularly when high tides stop water flowing out to sea.
"It's accepted that the land the council owns is basically blocking the free flow of water.
"We're helping to mitigate the flooding by opening that up," Hellberg said.
While the improvements will reduce flooding, the low lying area will always be flood prone, she said.
The community and Waste Management, which runs the transfer station, need to be consulted about the plans for drainage improvements before final decisions are made.
The transfer station site is potentially contaminated from its past use as a rubbish dump, but Hellberg hopes work on the new drain can be completed within the next year.
The drain would connect with a wetland behind and a box culvert would drain water under Ostend Road into Anzac Bay.
She hopes improving the flow between the wetlands and the sea will have environmental benefits too.
"We want to mimic a natural bottom and create the possibility for creatures to swim through the culvert."
After the floods last autumn, the council mapped 125 properties or areas on Waiheke where floods occurred.
Healthy Waters has taken over from Auckland Transport as the council agency responsible for managing stormwater on Waiheke.
By the end of the year, stormwater catchment plans will be developed for the western end of Waiheke.
The plans will focus on Tahi Road, Blackpool and Onetangi, where flooding has been particularly severe.
Auckland Transport has put roadworks on hold on Moa Avenue in Blackpool so better stormwater management can be included as part of the road upgrade.
A meeting will be held on Wednesday, August 16, from 5.30pm to 8pm at the Old Blackpool School Hall, to present options for tackling flooding in Blackpool.