Posted: 13 December 2006
100,000 litre sewage spill prompts NRC warning
An estimated 100,000 litre raw sewage spill into a Whangarei stream has prompted a warning to contractors to obtain local authority approval before working on public sewerage systems.
The Northland Regional Council has taken enforcement action against a Whangarei-based contractor and the Whangarei District Council after the December 1 incident involving the allegedly unauthorised closure of a valve on an Onerahi sewage pipeline.
Andrew Carvell, a Domestic Wastewater Management Officer with the Northland Regional Council, says the valve closure saw raw sewage back up in the pipeline before overflowing from a manhole and into a tributary of the Waimahanga Stream, near the corner of Old Onerahi Road and Riverside Drive.
The spill – estimated at 100,000 litres – killed native fish and other aquatic life in the tributary before eventually reaching the Waimahanga Stream, rendering it unsafe for swimming or shellfish gathering for several days.
Mr Carvell says estimates of the amount of time the sewage spilled for range from 25 to 90 minutes, but it was eventually halted when the District Council was alerted and shut down pumping equipment at Onerahi.
The spill occurred during maintenance work when a contractor working on a private sewerage system in the Onerahi area inadvertently closed off a District Council sewerage system valve.
Mr Carvell says the Regional Council issued a $750 infringement notice to the contractor and has served an abatement notice on the Whangarei District Council requiring it to secure the valve involved to prevent similar incidents in future.
He says the Regional Council opted not to prosecute the contractor in this case for a number of reasons, including his previously good record.
“However, this incident serves as a valuable lesson to Northland’s contracting industry to ensure before starting a job that they are familiar with any public sewerage systems involved and have obtained prior permission to make any alterations to it, including opening and closing valves.”
Mr Carvell says the Regional Council investigates dozens of sewage spills around the region annually.
“In far too many cases, these spills involve some element of human error and could otherwise be avoided.”