|
|||||
New Zealand Engineering 1999 September Feature Project Manukau
State of the art You can perfume, sanitise and deodorise the language as much as you like but the bottom line is still the same: shit stinks and people don’t want to live near it. This simple but compelling reason is why Watercare, Auckland’s water and wastewater treatment company, is spending $451 million over the next five years on Project Manukau, New Zealand’s largest civil engineering project. Auckland has almost always had a sewage disposal problem. In 1888 typhoid was ravaging the residents of Ponsonby, and between 1878 and 1908 seven reports were produced on the problem. This cycle of thirty-year arguments, stopgap measures, Royal Commissions of Inquiry, plans, reversals of plans, and eventual expenditure has been a feature of local government in wastewater planning for over a century. It certainly has not been limited to Auckland either. It was not until 1914 that Auckland’s first processing system, an outfall at Okahu Point designed by M Taylor, was completed. Even then, by the mid-1920s pollution at Orakei was unacceptable. While this early attempt to control sewage pollution was going on several new sewers discharging raw sewage were being put in all over the burgeoning city. In 1931 the Drainage Board produced a report recommending a treatment plant on Motukorea (Brown’s Island) which was argued about until 1954 when incoming Board chairman D M (later Sir Dove Myer) Robinson agreed to back off the scheme. The Drainage Board did, however, succeed in establishing the Manukau Sewage Purification Works which was commissioned in 1960. When Auckland Metropolitan Drainage Board chief engineer, C.C. Collom, introduced the Manukau Sewerage Scheme to New Zealand Engineering readers in February 1957 the best population projection for Auckland by the year 2000 (excluding the North Shore) was 640,000. The �9 million project was designed to cater for a "saturation population of the metropolitan district" of 800,000. On Census night 1996 Auckland’s population was 1,077,000. From Mr Collom’s paper one can soon see that operational cost savings weighed heavily as a design criteria for the original Manukau sewerage scheme. The use of chlorine as a sterilisation agent is discounted not for the environmental reasons which surfaced thirty years later, but rather because of its high cost and uncertain availability. The wide area of the oxidation ponds allowed the designers to reduce the energy demands from aeration pumps by taking advantage of the photosynthesis of algae in the ponds. Mr Collom almost accurately predicts a 50-year life for the sludge lagoons which forty years later are now being decommissioned. But having established the Manukau system, which reached its design limits in 1972, local government went back to its old habits of argument, commissioning reports, Royal Commissions of Inquiry and implementing stopgap measures for nearly another thirty years. The Drainage Board had become the Auckland Regional Authority in 1963 and oversaw a major upgrade of the Manukau system in 1980; but by 1987 it was obvious the area needed a complete rethink. In August 1987 an issues and options paper was released to the public. The resulting 700 submissions were reviewed and stage two of the study was given to parallel studies by the ARA’s consultants, Beca Carter Hollings & Ferner; the Tainui/Ngati Whatua Joint Committee on Wastewater Management; and Drainage Department staff. Further consultation with the public and over 7,000 replies threw up a new option, disposal into the Tasman Sea off Cochranes Gap, which was adopted by the Auckland Regional Council as the preferred discharge point in August 1990. This was reversed in favour of Manukau again in December 1991 with the passage of the Resource Management Act 1991 which created a ten-year deadline before the resource consent for the Manukau sewerage scheme would automatically expire. In November 1992 the assets and operation of the wastewater system were transferred to Watercare Services, a local authority trading enterprise owned by the Auckland Regional Services Trust. It was from this point that the agency responsible for obtaining resource consents for operating Auckland’s sewerage system became clear and the business of negotiating for and obtaining those consents could begin. State of the
Art For a start those oxidation ponds placed over putrefying mudflats which represented an operational cost saving in the eyes of Mr Collom and his contemporaries (but became an eyesore to everyone else), will be replaced by giant reactor/clarifier tanks (nicknamed "Donuts") which will effectively do the same thing but in a contained environment. The sludge which had been stacked in lagoons Mr Collom had almost accurately predicted would last for fifty years will, once Project Manukau is completed, be thickened, put through anaerobic digestion to produce burnable methane, dewatered, stabilised with lime and trucked off at a rate of 20 truck-trailer loads a day. The clarified water will be sterilised using what will be the world’s largest ultraviolet light steriliser, and then the practically clean water will be pumped out into the Manukau Harbour at high tide at a peak rate of 25 cumecs (cubic metres) per second, a rate which is greater than the Wairoa River. As a result the total energy draw of the Auckland sewerage system will rocket up to a peak net draw of 23 megawatts, the equivalent of a small power station. At the same time Project Manukau will see a restoration of the mudflats around Puketutu Island for both development and as a habitat for migratory birds. Watercare planning manager, Craig McIlroy, says nobody is quite sure as yet where 400 tonnes of biosolids per day is going to be shipped 365 days a year. He says New Zealand has a history of leaching its soils and it may well be that Watercare could become a major source of soil nutrients in future. He also says that while some energy will be able to be generated on site the cost of energy will become a major part of the new plant’s operational costs. How exactly this will be paid for is still not known but it is clear that five years from now six of Auckland’s cities will have the benefit of the most state-of-the-art sewerage system in the world. Achieving all this on time, to budget and within resource consents is the task of Manukau Wastewater Services Ltd, a consortium comprising Fletcher Construction, Lend Lease Projects, CH2M Beca (a joint venture between USA based CH2MHILL and Beca Carter Hollings & Ferner), and New Zealand Water Services (a subsidiary of Suez Lyonnaise des Eaux and Lend Lease Projects), appointed in February 1998. Managing the resource consents and the interface between the Auckland Regional Council, Manukau City Council, local residents and Manukau Wastewater Services Ltd remains the task of Watercare Services, which obviously owns the whole project. For Watercare Services Project Manukau manager, Bob Vilker, who has project managed similar scale wastewater projects in the United States, the issues involved in Project Manukau are "uncannily similar". He says even though he has worked in different countries, different cities and with different projects the issues are more striking for their similarities than their differences. He says if there is any notable difference it has been the huge amount of consultation with local communities involved. "This is really the first major project completely under the Resource Management Act and while the consultation has definitely added value you do have to question whether that value is justified compared to the effort sometimes," he says. The process for developing Project Manukau is broadly a build-transfer one but because of the sheer size of the project, communication and consultation between Watercare Services and Manukau Wastewater Services has been built in from the beginning. Indeed the whole contract turns on the management plan approval process which is a system for constructing a system. Because the complete design of Project Manukau was not known from the outset this process for developing management plans, complete with their own resource consents, was developed. There are currently ten active management plans including "operations", "construction", "contingency" and "foreshore redevelopment". Teamwork That significant language also includes liquidated damages which would bring water to even the toughest design-construction team’s eyes and the Manukau Wastewater Services Team has no intention of incurring any. Of course it has to be remembered that that team did not exist eighteen months ago. Back then the team was working for employers like Fletcher Construction, Lend Lease and Beca Carter Hollings & Ferner. Contract manager, Peter Mills, says the team has coalesced extremely well. "I suppose one doesn’t get to say it often enough in the day-to-day operational side of things but this [management team] is an extremely focused and talented group of individuals who come from a strong background in project work. So although we have our issues every now and again I have to say the way this team has worked is a credit to the professionalism of everyone involved." Building a new sewerage plant where one already exists is not necessarily the easiest way to do things. The flow from Auckland, which can vary by a factor of five from 2.8 to up to 15 cumecs plus, because much of the Auckland sewerage system is also the stormwater system, keeps on coming 24 hours a day. If the mixture in the oxidation ponds is misbalanced then before very long the photosynthesising algae die in what is called a "pond crash" and the residents of Mangere will not be the only ones kicking up a serious stink. Decontaminating and decommissioning the oxidation ponds is therefore a matter which must be handled with great sensitivity. For David Carter, co-leader of the foreshore rehabilitation design team, the design process cannot be carried out in splendid isolation and there is constant interaction between Watercare and the on-site construction team. This is also why MWS process engineer, Peter Flynn, and operations manager Mike Jury are closely involved with Watercare operations staff. Their job is to design the systems processes for, and train Watercare staff on, the new system as it is brought onstream and run in parallel with the old system. As more and more of the new system is brought on line the old system can be decommissioned, until the new completely replaces the old. The whole team agrees there is nothing like a quick drive around the 700 hectare site to give one an appreciation of the scale of the undertaking which they are engaged on. Just the size of each of the reactor-clarifier units is itself impressive enough. And the first stage of the plan involves putting in three of the final nine so that oxidation ponds can be taken off line. The first step, naturally enough, was digging out the foundations. This involved moving 700,000 cubic metres of spoil (peat and sand) in an operation called the "big dig". This was completed in June almost a month ahead of schedule. The record for one week’s work was 28,000 cubic metres and 618 vehicle moves a day, 40 percent ahead of target. In the meantime the floor of the first reactor-clarifier was poured in the "big pour" on 20 February, which meant concrete was kept coming in a continual stream totalling 1,100 cubic metres from 4.00pm until 1:30am. Three concrete works in Mangere, East Tamaki and Takanini kept the concrete coming and drivers managed to pleasantly surprise residents and hoteliers by keeping noise to an absolute minimum. After the floor was completed 104 precast concrete panels fabricated on site to save transport costs and noise were swung into position to form the inner and outer walls of the "donut". These nine metre tall panels will be backfilled to produce a final three metre high wall. Site manager for the processing plant, Bruce Habershon, says the composition of the soils (peats interbedded with silty sands) for the foundation turned out to be far worse than originally thought. "It wasn’t so much sand with peat lenses as peat with sand lenses," he says. Although this created additional foundation problems these have now been resolved. Another element resolved along the way was the baffles in the reactor/clarifier chambers. These will be made of ordinary treated plywood which Australian 20-year tests have found will stand immersion in a wet and biologically active environment for decades. Once the "donuts" are operating it will be possible to demolish the existing fixed growth reactors and replace them with yet more "donuts". In the meantime rehabilitation site manager Steve Hart’s team is already well on its way with the dredging of the number one oxidation pond. The rehabilitation work is valued at about $150 million and is therefore a very major part of the overall project. Dredging of the oxidation ponds and the sludge lagoons is already well underway. This will involve the most extensive treatment and movement of material, with 300,000 cubic metres of sludge from the sludge lagoons and four million cubic metres of sludge from the oxidation ponds to be treated, dried and disposed of in the landfills created by the project. Safety Working on a live sewerage site is naturally enough not without its hazards. All of the 250 staff on site have been vaccinated against hepatitis and the safety standards are particularly rigorous. In fact, although nobody wants to tempt fate, the site has lost zero hours to workplace accidents in the first year of 350,000 man-hours worked. This in itself does not come about by accident. The first thing you see as you come into the site carpark is a large sign proclaiming the safety record. A visit to the men’s toilet finds it plastered with safety notes and reminders exhorting workers to treat every potential safety and environ-mental hazard seriously, from the smallest diesel spill on up. Safety records were a matter of contention before Watercare appointed Manukau Wastewater Services and Peter Mills is determined to vindicate Watercare’s faith. "We’ve got there by setting exacting safety standards, having complete buy-in by all senior managers, by employing a full-time safety manager who has worked internationally and knows these standards have been met elsewhere, and by getting supervisors and foremen to believe in these safety targets with education and incentives. You have to establish a complete safety culture." he says. The total Project Manukau job will take over five years to complete. During that time there is also the critical point of money. Beca Carter Hollings & Ferner chief executive, Richard Aitken, says forming design-build-transfer partnerships is complicated by the different risk management strategies of their constituents. Consultancies are used to selling technical time while contractors work on a percentage margin on physical work and follow a risk strategy of pluses and minuses on good and bad jobs. He points out there is no problem when everything is running smoothly but the trick to establishing such a joint venture is the need to consider the down side. "It is relatively easy to work out how you share success. Things only get difficult when you come to working out how you would share failure. You have to have a situation where everyone is comfortable with the arrangement irrespective of the outcome." Watercare is paying Manukau Wastewater Services in stages as critical milestones are met. But where does an organisation with an annual income in the order of $135 million a year from city councils and corporates, get $451 million from? The short answer, according to communications manager Owen Cook, is debt. Watercare is arranging finance from international lending institutions and may issue bonds to pay for the Project Manukau development based on its Standard and Poors A+ credit rating. How will it repay that debt? Well, that is another matter which is not precisely known. The answer will almost certainly depend on the upshot of the Ministry of Commerce’s options paper on the water industry which is currently before Ministers. However this is one situation where accountants can argue all they like about the money, but Auckland needs a proper sewerage system and it needs it soon. Hopefully, with the completion of Project Manukau, Auckland will also get a system for developing its sewage processing system which does not need to reach critical levels again before the hard decisions are taken. Peter King, editor |
|||||
 |
|
|
|
