Nearly 1000 sites on council contaminated list

Close to 1000 sites around Marlborough – including numerous residential areas – have been included in a district council list of potentially contaminated sites.

The sites, some of which were polluted with heavy metals, chemicals and fertilisers, totalled 960, but many had acceptable levels of contamination or the contamination was being managed or fixed.

Only four sites were found to be contaminated beyond acceptable levels – Dashwood Timber, near Renwick, London Quay, in Picton, and sections at 57 and 57A Redwood St.

Landowners are not obligated to investigate or fix contamination, unless it is related to a resource consent application to develop the land.

Marlborough District Council environmental scientist Colin Gray said the Dashwood contamination was minor and related to treatment of wood, while lead found at the Redwood St site may be related to a former house there.

Mr Gray said the landowner, understood to be a developer, must remove the contaminated material under subdivision consent requirements, but this was unlikely to be a major undertaking.

"I don't know how much there is but in these situations typically it will only be topsoil contamination ... lead doesn't tend to leach."

Once the contamination was removed the site would be tested. A house occupies an unaffected section of the site.

Meanwhile, the contamination at Dashwood is likely to be investigated this year after the council secured some funding for site investigations, Mr Gray said.

The council own the land at Dashwood Timber.

The contamination at London Quay, where copper, mercury and tin have been found, was caused by historic harbour use, he said.

Some dredging of the area was done as part of the council's multimillion-dollar redevelopment of the site, but the site was still contaminated, although levels were dropping. "Nature is helping (fix) it, just the ageing of those contaminants and things like fresh sediment covering it up.

"It's a matter of monitoring the site and letting nature fix it."

Many residential areas were included in the list of potentially contaminated sites.

This was usually because they were once market gardens, orchards or home to glasshouses and had now been converted into housing, Dr Gray said.

"Typically in horticultural activities and glasshouses they used heavy metals, like arsenic, and they last a long time ... hundreds of years at least."

Also affected were areas around the former Blenheim saleyards where livestock dipping took place.

However, Dr Gray said all potential subdivisions are investigated and contaminated soil removed or monitored.

Residents should not be concerned, he said.

"I would be more concerned about (sites of) old garden sheds and the chemicals that may have leached there, because those sites haven't been investigated."

Another example was the practice up till the 1960s of using lead-based house paint.

Any removal of the paint may mean a property is contaminated, but as it is not subject to investigation by the council the contamination was unknown, he said.

Other sites included in the list were service stations, railway yards, gasworks, landfill sites, car workshops, scrapyards and cemeteries.

Dr Gray said information on potential contamination was available on Land Information Memorandum (LIM) and Project Information Memorandum (PIM) reports, but some landowners were surprised to find their properties on the list.

About six had indicated they were interested in the contamination or potential contamination being investigated.

- The Marlborough Express