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House of Assembly - Fifty-First Parliament, Second Session (51-2)
2008-04-09 Daily Xml
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Parliamentary Committees

PUBLIC WORKS COMMITTEE: LITTLE PARA DAM SAFETY UPGRADE

Ms CICCARELLO (Norwood) (11:28): I move:

That the 285th report of the committee, on Little Para Dam Safety Upgrade, be noted.

The Little Para Dam was completed in 1979 and consists of a concrete-faced rockfill embankment 53 metres high and 255 metres long. It has a capacity of 20,800 megalitres and supplies water to the Little Para water filtration plant, which serves Salisbury, Elizabeth, Parafield, Para Hills and Mawson Lakes.

Dams are carefully designed at the time they are constructed and it is hoped that failure of a dam is unlikely. However, because they age and are subject to changing natural forces, they eventually require remedial action in order to ensure that they do not fail and cause loss of life and significant damage to the communities and the environment in the flood plain below the dam.

The most significant risk to the dam is washing away the crest following a large storm. The current spillway has a capacity to bypass a one in 10,000 year storm. However, because a failure can inundate a flood plain containing 35,000 people, dam safety guidelines recommend that the spillway be upgraded to mitigate the probable maximum flood to one in 10 million years without failure. This project involves:

Construction of an additional 52-metre wide spillway to prevent overtopping and failure of the dam during extreme floods;

Raising the dam crest by one metre to increase freeboard and improve spillway capacity;

Modification of the existing spillway to accommodate deeper flows;

Checking the hold-down anchors of the outlet tower to ensure stability during earthquake; and

Replacement of vegetation removed during construction and increasing planting area to ensure the project is carbon neutral.

Proprietary fail-safe tipping gates at the head of the new spillway will maximise storage during normal floods and minimise the frequency of the flooding of downstream properties. The use of this innovative technology will reduce excavation by 220,000 cubic metres and generate savings of approximately $1.8 million. This work will reduce the risk posed by the dam and ensure that it complies with current guidelines.

Because large earthquakes are rare in South Australia, catastrophic failure of the Little Para Reservoir is not likely as a result of an earthquake. However, if the intake tower collapses, the contents of the storage will be lost in an uncontrolled manner. The tower is currently stabilised by anchors into the rocks below, and these may have deteriorated over time. During this project, the tops of these anchors will be exposed, and they will be physically tested for structural adequacy. If any remediation is required, it will be undertaken under a separate contract. This safety upgrade will:

reduce the risk of failure of the reservoir embankment during flood,

increase the security of the water supply system serviced by the Little Para Reservoir; and

increase the safety of the population living below the dam.

The portfolio risk assessment for Little Para indicates that a flood failure of Little Para could flood a population of 35,000 people and cause $2.6 billion to $2.8 billion in damage. Therefore, the dam has been placed in the extreme risk category because of the potential to cause loss of life, economic loss and loss of water supply to a large area.

Twenty options were costed, with the potential least cost options being for a tapered side channel spillway or a narrow unlined fuse-gate spillway. The fuse-gate spillway contains a proprietary gate component that has a much smaller environmental footprint than the tapered channel. This option is being pursued and a fixed price is being obtained for design and construction to reduce project risk.

A total of 270,000 cubic metres of rock will be excavated (instead of 494,000 cubic metres for the next cheapest option), and the overburden will be landscaped on site, as it is contaminated with a noxious weed. The rock fill will be used for roadworks on site, with the bulk of the high quality rock shipped off site for other construction projects. The major project risks include:

dust, noise and traffic nuisance during construction;

impact on endangered plant and animal species;

damage due to design errors;

rock excavated from the spillway being unsuitable for construction purposes;

spreading of noxious weeds; and

failure to meet peak demand during construction due to low dam water levels.

Strategies have been developed for all risks, and they will be reviewed regularly during the project. These strategies include: independent third-party assessment; an environmental management plan; a traffic management plan; core drilling prior to design completion, keeping dam levels close to the maximum allowed; and the use of a raised access road and coffer dam during construction. Construction of the project is expected to be completed by June 2009 at an estimated cost of $15 million, with only a negligible change in the operating cost of the reservoir.

Based upon the evidence presented to it, and pursuant to section 12C of the Parliamentary Committees Act 1991, the Public Works Committee reports to parliament that it recommends the proposed public work.

Mr PISONI (Unley) (11:33): The opposition obviously supports the project; however, it is a very small project in the overall provision of water infrastructure for South Australia. We are seeing the difficulties South Australia is experiencing at the moment whilst it struggles with its water infrastructure. Certainly, I know that in my electorate houses are cracking, and an article in The Advertiser the other day highlighted that not only Unley but also areas such as Parkside and Goodwood are very severely affected by cracking due to the drying out of the clay soil.

We have seen a number of pipes burst, and in Unley a week rarely goes by when we do not see a small leak popping up from the bitumen somewhere in the electorate. Of course, this leads to significant cost and inconvenience for it to be fixed in a hurry.

Having said that, sometimes I have witnessed leaks lasting for up to two weeks before they are attended to and, of course, being the diligent local member that I am, I am on the phone every day whenever I see a leak to get it fixed and save that water. But we get the same story that this is happening all over the place and we can do only so much in a day.

So, it is important that we maintain and continue to grow our water infrastructure, and methods of catching water and providing water to residents here in South Australia, particularly with the Premier's plan to increase our population in South Australia, which he has now brought forward from 2050, I believe, to now 2032, to two million people. It is imperative that in order to do that successfully we must have adequate water infrastructure, particularly in our cities.

I know how frustrated some of my country members are about the way water is being managed for rural producers in South Australia, and yet we are seeing no restrictions on trade in the commercial or manufacturing sector. I am sure that the member for Hammond will have something to say about that a little bit later. I know he is a strong advocate of water resources in South Australia. I am happy to tell this chamber that not a single party meeting goes by when the member for Hammond is not thumping his fist on the table and expressing his frustration with the way water is managed in this state.

So, obviously we are very keen to see that our water assets are maintained—some would argue at a very slow pace, a very slow rate. I stand here as a supporter of this project, and obviously there are wider benefits for the local community in improving their safety and removing the risk that they have in the longer term by dealing with this maintenance program now and not waiting until later on.

The Hon. P.L. WHITE (Taylor) (11:37): I rise to support this project, as a member of the Public Works Committee who heard the evidence. It is very well considered expenditure of some $50 million to upgrade the safety of the Little Para reservoir, which not only services the Little Para water filtration plant and those northern suburbs of Salisbury, Elizabeth, Parafield, and all around there but of course if the dam was to fail there would be catastrophic problems. It is a dam that has a capacity of nearly 21,000 megalitres, so all of that water would flow not only into the electorate of my colleague the member for Little Para but also into mine. We have had enough flooding incidents in that region, I can assure you, in recent times.

I am very keen that this work proceeds. The work is due to be completed mid next year. It is an upgrade. It is a 30 year old dam that is due to have this upgrade because, while the current spillway, for example, has a bypass capacity for a one in 10,000 years storm, we do have the possibility of failure that would inundate all of those surrounding and lower lying regions of quite dense population. So, the safety upgrade will reduce that failure during a flood event, increase the security of that water heading into the Little Para reservoir and, of course, people in surrounding suburbia will be able to sleep safer at night. It is a big job—nearly 300,000 cubic metres of rock will have to be excavated at quite some expense—but it is a work that is due at this point in time, and I support it very strongly for the added security that it will give to our water supply and to surrounding suburbs.

Mr PENGILLY (Finniss) (11:40): I also rise to support this project; I think it is a good project. As the member for Taylor has indicated, it is in the best interests of that most modern dam that the state has built in Little Para. I think it was the last one that was built, and it is the most modern dam in the system, so I think it is appropriate that this action now take place.

The good news is that, given that this is being put in place as a safety precaution, the members for Ramsay and Napier can sleep soundly at night in their respective suburbs of Norwood and Springfield and not worry about their constituents getting washed away. I think it is good news for them. A good part of it is the revegetation aspect and the fact that the landscaping and everything around that dam will also be improved quite substantially.

The floods that we get from time to time are of enormous concern and, as we go on developing the Adelaide Plains and that very flat section of land that is to the north of Adelaide, we have to have in place sufficient security measures to make sure that when we get a flood—and we will; we will get a big rain, don't worry—everything is safe and sound below and nothing disastrous happens.

My view is that the floods will come sooner rather than later. I hope that this project goes ahead quite rapidly because after the sustained period of drought that we have had you generally get a particularly wet period. Whether that happens this year, next year or the year after, none of us knows, but it will happen and we have to be prepared. Yes, I am pleased and I was pleased as a member of the Public Works Committee to support this project.

The Hon. R.B. SUCH (Fisher) (11:42): I will be very brief. I support this upgrade to the Little Para dam. Having the reservoir in my electorate upgraded some time ago, I know that this is an essential project. This is the result of a study done some years ago (which originated in the US) which found that some of the dams there were not safe and they collapsed with tragic consequences. So, standards in Australia have been raised, and so they should be. It is not that Little Para is likely to fail, neither was that the case with Happy Valley, but it is better to be safe rather than sorry and have lives lost and people's property damaged.

I note that the report talks about minor works planned for Kangaroo Creek. I would hope that major works are planned for Kangaroo Creek because originally the height of the spillway there was to be raised much higher than it ended up being. It was compromised in the sense that it became a flood control issue as well. I think that Kangaroo Creek's major spillway should be raised substantially. It would retain a lot of water and a stormwater spillway could be built just below the main spillway. I commend this report. It is a good safety measure and I commend SA Water for continuing to upgrade their reservoirs. I note that many others are still to be done as part of a $145 million project.

Mr PEDERICK (Hammond) (11:44): I, too, rise today to support the motion to note the report on the upgrade of the Little Para reservoir. I note that it is one of a string of reservoirs that supplies Adelaide's water and is also backed up by pipelines from the River Murray. This one takes supply from the Mannum pipeline when there is a lack of inflows, not just for the Little Para but also other dams in the hills. The government's policy initially was to expand Mount Bold. That was to expand—

Mr Pengilly interjecting:

Mr PEDERICK: Yes, a backflip. The government was going to expand Mount Bold by 200 gigalitres (from 45 to 245 gigalitres), yet, suddenly, it has gone to somewhere in the Mount Lofty Ranges.

The Liberal Party is against the construction of Mount Bold and, if the government does go down this path of increasing storage in the Mount Lofty Ranges, we will need to have a very good look at whatever site is decided upon for a new reservoir or an expanded reservoir. I do not know what the government has done regarding inflow measurement and that sort of thing. However, the Minister for Water Security told a group of people at Goolwa on Sunday that 139 sites are now being considered for a proposed dam.

Mr Pengilly: She made a big stuff-up, didn't she?

Mr PEDERICK: Yes; just a minor issue there! Any proposal for a dam, a new reservoir or an expanded reservoir in the Hills should be avoided. Plenty of rain falls on the City of Adelaide area which could be captured. The technology is there, as has been proven by Colin Pitman in the Salisbury council, with the wetland project supplying about nine gigalitres of water to industry in the north. I know that Michell's wool-handling facility in the north contracted for a lot of this water to save them from purchasing water from the normal SA Water stream.

One problem the government has in the Hills is that there is a threatened loss of species, which goes against the State Strategic Plan in terms of both flora and fauna at Mount Bold . That is why the government is doing a back-pedal. We saw an interesting situation, where the government came kicking and screaming into the picture with a desalination plan—which we came up with.

Ms CICCARELLO: On a point of order, Mr Speaker.

The SPEAKER: The member for Norwood.

Ms CICCARELLO: I ask the speaker to come back to the substance of the debate, which is the Little Para reservoir, and not to continue with a general discussion about what is happening elsewhere.

Mr PEDERICK: No worries.

The SPEAKER: Order!

An honourable member: What is the point of order?

The SPEAKER: Order! I must admit I have not been following the debate very closely, but I do remind members to speak to the debate.

Mr PEDERICK: Thank you, Mr Speaker. I am discussing desalination because I believe that part of the program is for desalinated water to be piped back into reservoirs and, as reservoirs are the topic, I have reverted to that. Little Para may be one of those reservoirs. I am not privy to the documents and the research that the government has been doing. However, I am aware that part of the study on desalination involves storing the desalinated water in the dams. While I am on the topic of desalinated water which will be pumped into reservoirs, I wonder what will be done with the cleaned-up water from the pilot plant. That is something we will learn about down the track: whether they will be pumping that straight back into the sea and not using something that has been cleaned up.

In conclusion, I certainly support the remediation works planned for the Little Para dam. I note, with interest, that the anchors on the intake tower will be monitored. If any work is needed to be done on those intake towers, I hope that it is done appropriately. I commend the motion.

Ms CICCARELLO (Norwood) (11:49): I commend the report to the house.

Motion carried.

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