Odour from the facility in the city’s north east is of concern to neighbouring communities. Recent investigations have shown that it is mainly caused by landfill gas (an equal mix of carbon dioxide and methane), not from the tipping face.

Test areas found to be producing the gas are being recapped with a soil and bark mix. This will filter the odorous compounds from the escaping gas. Also being investigated is a system to collect the gas and perhaps use it to make electricity.

Staff say it will take time to work out which system or combination of systems will do the best job, but the work is being given priority.

An odour-control spraying system is also to be tested at the tipping face, where other changes are under way, including narrowing the working area and using more equipment to control and compact waste material as it arrives.

At the end of each day, at least 150mm of cover material is spread over the sloping tip face but staff are also currently testing a biodegradable plastic sheeting as an alternative way of covering each day’s refuse. If successful this would reduce the amount of cover material brought into the site. Other changes include restricting the delivery of, or immediately covering highly odorous loads, moving the area where biosolids cover material is prepared to the far north east of the site away from the closest houses, and rehabilitating the previous preparation area where water tended to pond.

The work being done to improve the operation at Burwood has to do with the Council’s resource consent conditions. In May this year the CCC got Environment Canterbury (ECan) approval to keep operating the Burwood Landfill until May 2005 or until the planned regional landfill opens, whichever comes first. Hearings into the new regional landfill got under way earlier this month.

Council is talking to representatives of two organisations which have objected to ECan’s May decision.

One of the objectors has said it is worried about potential health risk from material it believes will be in the landfill gas. Council staff report that the evidence from other recent landfill consent applications around New Zealand is that there is no such risk.

However, independent consultants will be asked to test and analyse Burwood’s gases to make sure this is so. The results will be reported to the City Council as soon as they are available.