12 December 2012

Horizons hears report on City landfill

A report on the impact of Palmerston North City Council's landfill on the Manawatu River was heard by Horizons Regional Council's Environment Committee today.

Horizons Regional Council instigated a two part investigation into the impacts of PNCC's landfill on both ground and surface water in 2011 in response to public concern.

The landfill lies on the edge of the Manawatu River and has a lined section which operated from 1951 to 1995 and unlined section, in operation between 1995 and 2007. The landfill ceased operation in 2007 and was capped to minimise water infiltrating the site.

Although no longer in operation, leachate continues to be generated at the PNCC landfill and has the potential to cause both environmental and ecological effects on waterways if not managed correctly due to a range of chemicals and compounds.

Currently, leachate is collected from the lined section of the landfill site and treated through the waste water treatment plant. Leachate from the unlined section cannot be collected.

The concern that led to the investigation stemmed from the disposal of coal tar in a specifically designed cell in December 2000. Previous investigations of this cell were undertaken by the Parliamentary Commissioner for the Environment in 2001. No leakage was detected at that time.

Results of the most recent investigation found traces of coal tar in the leachate from the lined section but Horizons' manager of science Dr Roygard said the impact of this is being mitigated through the treatment of the leachate at the waste water treatment plant

"We monitored a total of 17 sites along the stretch of the Manawatu River and found no trace of the leachate from the lined section of the landfill. This indicates that somewhere through the treatment process the effect is being mitigated," explained Dr Roygard.

However, water was found to be seeping from the landfill into the Mangaone Stream, elevating levels of ammonia, zinc and phosphorus. Remedial action is currently being undertaken by PNCC.

Other concerns raised were the potential impact on the river from herbicides and pesticides.

Dr Roygard said evidence of these were found in the groundwater nearby the landfill but were not detected in the river, suggesting these were being diluted to an undetectable level by the time it reached the river.

The report made a series of recommendations to the consent holder including additional sampling of the landfill, groundwater and river to monitor any change to the impact of the landfill overtime. Horizons is working closely with PNCC ensure the on-going management of the site and that the recommendations in the report are put into practice.

ENDS

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