A site for collecting silt from Cyclone Gabrielle, located in Hawke's Bay. Entities collecting silt are responsible for ensuring that contaminated silt is handled correctly. Photo / Warren Buckland
A site for collecting silt from Cyclone Gabrielle, located in Hawke's Bay. Entities collecting silt are responsible for ensuring that contaminated silt is handled correctly. Photo / Warren Buckland
Yet-to-be-approved resource consents will likely determine where Hawke’s Bay’s contaminated Cyclone Gabrielle silt will eventually be laid to rest, and it could even be taken out of the region.
The cyclone deposited more than 2.7 million tonnes of sediment in the lower 5km of Esk Valley alone, the University of Canterbury and Niwa estimated using data gathered through high-resolution helicopter laser scanning.
Hastings District Council estimates that HDC and Hawke’s Bay Regional Council contractors have collected between 20,000 and 25,000 cubic metres of silt to date.
For the past month, residents of silt-stricken properties have been shovelling silt onto roadsides and out of their homes.
Most of the silt is not thought to be contaminated, but there are known sites with contamination, including the industrial area of Awatoto, which has been cordoned off.
Hawke’s Bay Regional Council runs one site for the disposal of clean silt, open to contractors only.
A council spokeswoman said it was still in negotiations with landowners to set up a large silt disposal site for contractors at a location between Napier and Eskdale.
HBRC, HDC and Napier City Council do not run any sites specifically for contaminated silt.
An HDC spokesperson said they have six sites that are operational for clean silt.
“If any sites are identified as contaminated they will be managed as required depending on the situation,” the HDC spokesperson said.
Raymond Burr is on the ground in Hawke’s Bay testing silt for contaminants.
A consulting director for soil testing service Qlabs, Burr said he had not been given a specific procedure for contaminated silts from any council, but companies dealing with contaminated soil had a standard procedure before Cyclone Gabrielle.
“Up until now, it [contaminated silt] has all been transported to Marton, to the containment site over there,” Burr said.
He said Qlabs had only just begun work on testing silt for contaminants across Hawke’s Bay and had not come across any silt that was contaminated yet.
“I think people are only now just starting to think about that sort of thing [soil testing]. Up until now it has been just get back on your feet as best as you can.”
He said silt and soil should always be treated as contaminated with bacteria, and people should get it tested if removing large amounts.
“If it is contaminated with something like petro-chems, asbestos and nasties like that, it has to go to a containment landfill,” he said.
“Whether the council is going to set one up [a local contained landfill] for contaminated silts, I don’t know.”
A Napier City Council spokeswoman said all silt collection sites were managed by HBRC, except for a temporary holding site in Awatoto.
“However that is only for Awatoto Industrial Zone silt that is ‘clean’ and that which we have tested and know has high levels of e.coli. We will treat the silt that has e.coli with hydrated lime,” the NCC spokeswoman said.
An HBRC spokeswoman said the council has tested silt in selected sites in rural areas across the Heretaunga Plains and it showed that, in general, the region’s silt is not likely to be contaminated.
Raymond Burr, consulting director for soil testing service Qlabs, said a specialised contained site would be required for contaminated silt, with the one used before Cyclone Gabrielle being located in Marton. Photo / Warren Buckland
HBRC Regulation and Policy Group Manager Katrina Brunton said the responsibility for testing potentially contaminated silt lies with property owners, and with the person or entity collecting and disposing of the silt.
“If the silt is contaminated, then the property owner needs to make arrangements with a suitably qualified specialist for removal,” Brunton said.
Hastings District Council said on its website it was not compulsory to test silt before moving it, but it asked property owners to provide their teams with information on the makeup of the silt to aid with selecting the right disposal site.
This means it is up to a property owner to decide whether they should test silt on their property to confirm if it is contaminated.
“Where silt is being stockpiled or discharged to a site by an entity (such as a Council, Horticulture New Zealand or private contractors), it is their responsibility to ensure that that the silt is free from contaminants and is suitable for discharge,” Brunton said.
Entities, including private contractors, picking up contaminated silt have to determine a site to stockpile and discharge it, and may need a resource consent from HBRC if there could be ongoing adverse effects on the environment.
“In the case of silt disposal, this should include managing and recording the source of any material, and representative sampling of silt that is collected and discharged,” Brunton said.
