Trial of new technology may reduce stormwater pollution by vehicles

For immediate release: Thursday 9 September 2004 New stormwater technology, now being tested in Tauranga, may eventually help reduce the environmental impact that vehicles have on the Bay of Plenty’s lakes, harbours and rivers.

Early last year, Environment Bay of Plenty asked Landcare Research to trial a low-cost treatment wall that can remove heavy metals and other pollutants from stormwater washed off roads. Though roading infrastructure represents only a fairly small part of an urban catchment, road stormwater accounts for a large proportion of the contaminants - up to 75% of heavy metals, up to a quarter of total hydrocarbons and half of the suspended solids.

The trial treatment wall was installed at the roundabout intersection of Hewletts Rd and Tasman Quay, a busy Port of Tauranga entrance, last year. Environment Bay of Plenty’s manager environmental coordination Bruce Gardner told the regulation and monitoring committee meeting last week that it was proving quite effective, filtering solids and capturing much of the dissolved zinc and hydrocarbons. However, it was not working as well with dissolved copper and lead.

Mr Gardner says the treatment wall is simply a shallow, concrete chamber layered with different absorption materials, like sphagnum moss and wood ash. Stormwater filters down through the layers before discharging into stormwater pipes.

Mr Gardner says the intersection selected for the trial provides “a very hard test” for the treatment wall. A huge amount of traffic passes through it, including loaded trucks turning on the roundabout to leave and enter the port area.

The trial will continue until June next year, with Landcare Research experimenting with different materials to find a mix that works best. Later, the regional council will assess whether treatment walls can be retrofitted into the existing stormwater infrastructure in key urban areas in the Bay of Plenty.

So far, the walls are being trialled in Hamilton, Cambridge and Henderson.

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