A faulty gas well cap is the likely culprit behind a spate of Spicer Landfill odour complaints that were lodged with Porirua City Council on Saturday 10 June.

David Down, Manager, Water and Waste, says 50 complaints were received from Tawa residents mostly between 1-6pm with an unusually high proportion of complaints relating to a sulphurous smell and others reporting a rubbish type smell. He says that the regulator, Greater Wellington Regional Council, investigated and confirmed an objectionable and offensive odour was present.

Mr Down says that while extremely unpleasant in smell, the odour was not classified as harmful, and no harmful levels of hydrogen sulphides were recorded at the Council’s air monitoring station in Tawa.

"We’ve never had this many complaints in one day," he says.

"It’s disappointing to see this spike when we have actively been trying to manage and minimise odour issues at the landfill. Typically this month we’ve seen more like 3-13 complaints a day, mostly in the evenings or early morning citing a ‘rubbish’ type of odour."

Mr Down says the collection of data around odour has become more sophisticated in the past year.

"Having specific data indicating the type of smell has meant we’ve been able to identify and rectify the most likely cause of the sulphurous issue quickly."

Mr Down says a cap on one of the disconnected gas wells was found to have popped open discharging gas in relatively large volumes.

"We have over a hundred gas wells at the landfill. These collect the gas from the decomposing rubbish buried under the landfill and then a network of gas pipes connects to a flare where the gas is destroyed. At any given time, there’s around four gas wells disconnected and capped off so that plant and machinery can operate in the working area of the tip face (which moves around).

"The gas well at fault draws large quantities of gas out of the depths of the landfill. When it was disconnected and capped the fixing used on the cap was not secure enough and as the pressure built up the cap popped off. At the same time the light north-west winds on Saturday were conducive to dispersing the gas in the Tawa neighbourhood.

"The investigation of the ‘rubbish’ smell is still under way and we are looking into the ratios of clean fill that were mixed with sewage sludge on Saturday to see if that could have been a factor."

Porirua City Council continues to employ a raft of issues to manage odour at the landfill.

Plans to lodge applications this year to extend the life of the landfill out to 2050 are currently on hold. However, Council is looking to create more space within its existing landfill designation boundary and consent timeframe - a short-term solution to ensure that space for waste does not run out.

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