$14m Plan to Clean Up Polluted Hutt Stream

By NICHOLS, Lane

AUTHORITIES have unveiled a $14.3 million plan to clean up one of New Zealand’s most polluted waterways.

Lower Hutt’s Waiwhetu Stream is contaminated with dangerous levels of heavy metals and pesticides after decades of discharges from industrial plants at Seaview and Gracefield.

The worst-hit area is a stretch of streambed from Bell Rd railway bridge to upstream of Seaview Rd. Up to 30,000 cubic metres of sediment are thought to be heavily contaminated with lead, zinc, copper, mercury, arsenic and DDT.

Signs warn people not to swim or eat fish because of health risks.

Similar warnings were placed along Petone’s Te Mome Stream last month after Greater Wellington regional council found it had become heavily polluted with lead. Exide Technologies’ batteries-recycling plant nearby is thought to be the main cause.

Greater Wellington and Hutt City Council have been working for several years on how to deal with Waiwhetu Stream. A joint advisory committee issued a consultant’s report this week outlining a preferred plan of action with rough costings.

It recommends dividing the stream down the centre with a steel barrier, diverting water to one side, then excavating thousands of tonnes of contaminated sediment. The material would be drained and dumped untreated at Silverstream landfill, and the liquid poured into the city’s trade waste sewer. It would be replaced with sediment dredged from the Hutt River mouth.

The proposed cleanup method, estimated to cost $14.3 million, depends on community support. It is favoured over permanently diverting the stream through Hutt Park and capping the contaminated sediment. Costs could be substantially reduced if a small percentage of contaminant was allowed to escape uncontained, the report says.

Hutt City Council’s utility services divisional manager Bruce Sherlock said the estimated cleanup costs were probably conservative but the situation needed to be fixed. It was too early to speculate who would pay or whether businesses that caused the pollution would be made to contribute.

The committee would decide this week whether to accept the recommendations. Initial work could begin later this year. Proposed flood-protection work could also begin once a method to deal with the contamination was agreed.

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