Funds mean action on Onehunga contaminated land

19 January 2004

The Auckland Regional Council has received a grant of $46,200 from the Ministry for the Environment’s Contaminated Sites Fund to investigate Onehunga’s worst known contaminated land.

The ARC will contribute the other half of the cost of the work, which involves up to four rounds of sampling groundwater to establish contamination levels from this summer through to the 2004 winter and further development of options for remediating the site.

“We are grateful for the Ministry for the Environment funding. The Onehunga site is one of our ‘hotspots’ for historic contamination in the Auckland region and it’s important that we investigate the most practical and effective ways of cleaning it up for future uses. It’s in the middle of a vibrant business and residential area,” said ARC Environmental Management Committee chair Brian Smith.

The contamination comes from the former Farmers Fertiliser site that operated on what is now Henderson Place off Church St. In World War II large quantities of phosphate fertilisers were stored in the open on the site, due to concerns about shipping it through the Pacific during the war. In addition copper sulphate and other fertilisers were manufactured and stored on the site. Over the years, rainwater washed copper sulphate and other chemicals into the basalt rock and into the groundwater beneath the area.

In earlier investigations costing about $100,000, the ARC established that the area is heavily contaminated with fluoride, sulphate and phosphorus. The contamination historically extended in a plume in the groundwater from Henderson Place south and west to the Manukau harbour. A stream by a walkway running alongside Miami Parade used to have a visible bright aqua-green colour from the presence of copper.

“Problems from high levels of contaminants in the groundwater includes harm to aquatic life and limits to the use of the water for supply purposes. The groundwater is also acidic and it eats through concrete stormwater pipes causing leaks,” explains ARC Team Leader Contaminated Land Management Mary Manastyrski.

There is no evidence of any effect on the Onehunga drinking water supply as the plume is outside of the collection zone for this important resource.

“The contamination is not easy to remove because it’s within the water flowing through cracks in the solid basalt rock under the area. With this grant from the Ministry we will be able to determine how contamination levels have changed since we last tested the site in 1997 and whether it’s worse in summer or winter,” said Ms Manastyrski.

“Then with all of the data that we have collected over time, we will come up with cost-effective options most suitable to manage and remediate the problems that exist.”

“The ARC and Auckland City Council already have management steps in place to safeguard current businesses above the contaminated zone, and these investigations are also to confirm that these management steps are working,” said Ms Manastyrski.

Due to the historical nature of the contamination, who would pay for remediation and how or when it would occur is yet to be determined.

ENDS

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