A change in approach from Tauranga City Council has taken iwi representatives on its wastewater management review committee by surprise.

Iwi representatives are on the committee ostensibly to oversee the decommissioning of the Te Maunga sludge pond – as set out in the committee's role, and written on its agendas.

Te Maunga sludge pond.

This week the committee was presented with the proposal to either re-line the seeping Te Maunga sludge pond or build a new one, which will lie right next to a historically and culturally significant ridge that curves round behind Baypark Stadium.

It is a pre-European battles site and wars grave.

Use of the ponds is being reviewed because of uncertainty over the future of the present trucking arrangements which cart Tauranga's sludge to Hampton Downs, says the Tauranga City Council's wastewater engineer Graeme Jelly.

Wastewater management is about separating the solids and dewatering the sludge.

At Chapel Street it's digested and centrifuged to the consistency of wet top-soil before being trucked to Hampton Downs under a contract that has only two years to run.

It was the 'extremely competitive” nature of that contract five years ago that steered the council away from the ponds, says Graeme.

Two factors are pushing the review: the likelihood of increased transport costs when the trucking contract comes up for renewal, and the new Ten Year Plan.

Under the current plan there is $16 million set aside for constructing new sludge processing facilities at Te Maunga over the next two financial years.

Council is under pressure to reduce debt and Graeme's concerned the sludge money will be wiped in the new plan, unless there is a concrete proposal ready to go.

He's presenting three options; doing nothing, which may not be a long term option because of consent issues. Emptying, lining and partitioning the existing sludge pond to better suit the purpose; and building a new pond altogether.

The consent issues concern the seepage and the committee's role. The current pond consent allows for the current estimate of three tonnes of seepage per day into the headwaters of Rangataua Bay.

The seepage is monitored as is the ecology of the bay under a council fund also administered by the committee.

The seepage is recorded as wiping out the air breathing marine snail or titiko that lives in immediate intertidal area. Titiko is also kaimoana.

'It's kind of side tracking from what we are trying to achieve, which was to get rid of those ponds,” says committee member Reon Tuanau after the meeting.

'We are a little disappointed that the focus has been taken away from that.

'That's been our main focus to get those ponds decommissioned because of the pollution risk that they pose as they are.

'Titiko are one of our main kai that we harvest from that area, it is very much embedded in our tribal history.”

The sludge pond's attraction to the city council wastewater department is it presents a cost effective way of dealing with sludge in-house. The sludge settles in the pond with the water decanted off to the oxidation ponds. The sludge can be excavated from the emptied pond every few years, and buried on the adjacent former tip site.

By using the pond they get a 25 per cent reduction in solids by digestion and can de-sludge the pond every five or six years. If the pond is lined and partitioned they will know how long the sludge in each compartment has been in the pond. At present the old sludge is on the bottom with the new sludge over the top.

The waster water management review committee members expect to visit the site in the next few weeks.

The committee will also be discussing consent options with the regional council and making a report to the Ten Year Plan workshop on September 9 to secure funding.

There will follow design development and public consultation on the preferred option – expected by mid 2012.