Huge risk in cheaper' solution

Wanganui councillor Rob Vinsen speaks out about his fears over the continuing problem of the wastewater treatment plant.

We are in danger of making the same mistake all over again with the wastewater treatment plant.

I am decidedly uncomfortable with where the debate is heading on the solution for our malfunctioning plant, and it is the most important issue before council.

Politics is entering into the decision-making process and the risk of selecting a solution that fails again is high because of it.

On November 8, 2004, the newly-elected Vision-led council approved the Montgomery Watson Harza design and commissioned the detailed drawings to proceed.

The same council was driven 12 months later to ask officers to seek a review of the design and identify savings. Officers assessed that there was a net "saving" of $4 million by not completing the planned separation of stormwater and sewage in the Gonville and Castlecliff areas (cost $11 million) and enlarging the plant and lagoons "into a more natural shape" and modifying the plant ($7 million) to cope with the expected peak flows of stormwater.

This plan was approved by council on December 19, 2005. Whether this is the cause of our present malfunctioning plant is a question that will need to be answered by a qualified consulting engineer.

There is no doubt that minimising the cost was the major driver in selecting the design of the failed plant we now have, and my concern is that we could be about to follow the same path.

Cr Michael Laws now wants to put the design of the new plant out for tender - the usual process is to commission the design, have it peer reviewed and put the construction out to tender. He wants to appoint "three independent companies or persons" to assist council in evaluating these designs.

I believe that an invitation to submit further costed proposals is warranted but tendering for these proposals is entering into a statutory process that can only lead to least cost being the driver.

Council engineers Mark Hughes and Arno Benadie recommended Cardno BTO as the most qualified consultancy to work with. This company are specialists in wastewater treatment technology and have designed hundreds of plants in 41 countries around the world.

They also selected another consultancy to peer review the design. AECOM is also a specialist worldwide consultancy in wastewater treatment design.

On April 29, council accepted the Cardno BTO upgrade solution and instructed them to develop the design to a maximum cost of $250,000. Any change to that instruction now will waste most of that $250,000.

In 2003-04, MWH evaluated five options that varied in estimated capital costs from the selected $15.356 million up to $32.089 million. The working party selected the lowest cost option.

When the design was revised in 2005, after savings were identified, the estimated costs (which ended up higher than the actual costs) were the following:

Treatment plant $8,513,621; river crossing liner $639,987; pipelines $4,405,988; pumping mech $686,400; pumping electrical $281,615.

Total: $14,527,611.

So we got what we paid for - a plant that was missing some of the processes that were considered conventionally necessary. The design was described as "innovative" but has been described by Mathew Mates, consultant from AECOM, as "unlike any conventional design he had seen anywhere in the world".

The question is: Has the capital cost spent on the plant to date been wasted?

Not as I see it - the lagoons have cost $8.5 million of the $14.3 million spent on the plant. The balance was the cost of ancillary plant which, irrespective of the lagoons, would always have been necessary. Cardno BTO are proposing to add further processes to the plant but by adapting the current design, not discarding it.

These processes include: An anaerobic pond to provide primary treatment constructed within the existing aerobic lagoon; secondary treatment with contact stabilisation with new secondary clarifiers or sequencing batch reactors; UV disinfection; co-wasting of primary sludge and waste activated sludge from the anaerobic pond to solids handling.

The capital cost of this upgrade is estimated at between $17 million and $19 million. So, for a total cost of approximately $33 million, the upgraded plant is not considered to be excessively over-capitalised - the Hastings plant cost $35 million two years ago, and Napier's is under construction for $41 million.

Cardno BTO's proposal is essentially a conventional wastewater treatment plant process that has been proven over decades.

I do not accept that every expert is right, but I am discussing with several professionals, locally and internationally, what their view might be of the faults of our current plant and the proposed solution.

There are other suggestions that need to be discussed with the council technical team. This is the responsibility that councillors have - to satisfy themselves that all options are being looked at and evaluated.

I have received proposals that are either "cheaper" or "better" than the conventional Cardno BTO design, but accepting any of them is fraught with risk.

Pre-treatment of trade waste is an option evaluated by Cardno BTO. Their response is that the plant upgrade will still be needed because it is the process that is not working and the load is only exacerbating this.

I am looking for council to further evaluate this option, and a detailed study is needed. There are serious implications for both industry and ratepayers - the worst outcome would be to effect either heavy job losses or even higher rate burdens.

While the putrid odour from the failed plant has been a concern, we must not let haste and the lowest cost lead us into a solution that we need to readdress again in several years time.

We must do it once - and do it right.