$1m to move sludge as pipes fail
Wellington Water will spend about $1 million to transport sludge from Moa Point to the Southern Landfill after wastewater pipes burst.
Contractors are expected to make up to 150 trips a day to transport the sludge 10 kilometres from the Moa Point treatment plant to the landfill in Owhiro Bay.
Wellington Water expected to do that for at least five weeks while the broken pipes were repaired or an alternative pipe was set up. ‘‘We estimate we would be spending about $200,000 per week on trucking,’’ chief wastewater adviser Steve Hutchison said.
Six trucks were operating round the clock yesterday, loading ‘‘slurry’’ from the treatment plant and taking it to the landfill. Slurry is the substance left once solids such as faeces have been removed from wastewater. About 72 million litres of wastewater is received at the plant each day, with about 1 million litres of sludge then sent to the landfill.
Hutchison said the alternative to trucking the waste was dumping it into Cook Strait. ‘‘That was how the plant was set up as its last resort, as its backup, so we have the pipe work in place but we are undertaking all the work we can to avoid doing that. It would be partially treated but it would still not be treated to our usual standards.’’
The cost of repairing the pipes was yet to be determined, Hutchison said.
Contractors were working on the corner of Dover St and Adelaide Rd in Island Bay yesterday, assessing how to enter the tunnel where the leak happened.
‘‘We have a rough location of the break. It is in a tunnel, which is a live sewer tunnel, under the Mt Albert hill.
‘‘So it is a really difficult spot to get in and repair, and we are planning the work to undertake that entry safely.’’
It is the second time the pipes have failed in the past seven years.
Hutchison said both incidents were likely caused by construction ‘‘defects’’ when the pipes were installed in 1994.
‘‘These are, in our view, relatively young pipes. We still have to get in there to verify exactly what the cause of failure was.’’
Two pipes were in place but only one was used at a time, Hutchison said.
The in-use pipe was changed about every six months in order to share the load. It was ‘‘very unusual’’ for both pipes to break at the same time.
The pipes are owned and operated by the city council but managed by Wellington Water. In 1995, the council hired British company Anglian Water International to build and run a new $150m sewerage system, including the Moa Point plant and the failed pipes.
In the early years, the company faced multiple complaints from residents, including over a foul smell emitted by the plant and contaminated rubbish washing up on south Wellington beaches. In 2003, the Environment Court ordered the company to pay $30,000 costs after millions of contaminated plastic rings were discharged in Lyall Bay.