Mr McCARTHY - 1998-08-11
Has he been advised of the cause of the failure last night of the bridge crossing the Adelaide River on the Arnhem Highway, and what measures has he taken to re-open this very important crossing at the earliest possible time?
ANSWER
Madam Speaker, this bridge is vital to Northern Territory communications and economic output. To have it out at any time is not good - especially for people who live or own property on the far side of the river.
Some 2 to 3 metres in the middle of the outbound lane sagged after a road train passed over the bridge. I do not place any blame on the road train. In fact, I want to thank the driver of that road train – and thank goodness it was not a passenger bus! In my opinion, the damage was not caused by the road train. However, the driver felt the bridge wobble and had the sense to pull up on the other side and call the police, and to stop other drivers from travelling across. I do not want to give the impression that any blame should be placed on the road train operator. I would be stunned if the vehicle was overloaded enough to do the damage that has occurred. I want to place that clearly on the record.
A preliminary structural check was undertaken last night by engineers from the department. It appears that a pile supporting the pier has settled into the foundation material. When the bridge was constructed in about 1972, a solid base was found for the bridge piles, but it appears that over time this pile has been forced through that material and there is no proper foundation underneath to support it. It is as if it has punched through a crust that had developed there, and gone to the bottom.
The problem is, what about the other piles of the bridge? Are they in the same state or was it just this one? The department is now drilling to try and find whether or not there is a solid foundation in the bed of the Adelaide River - one of the great rivers of Australia and, indeed, of the world. It is a very large river. Members will recall that, before the Arnhem Highway was constructed, travelers had to cross the river at the 47 Mile, the Marrakai crossing, a long way upstream from the present bridge.
We are flying in some experts to assist us in geotechnical analysis of the riverbed. Our problem is that a Bailey bridge over the span will put extra weight on the 2 piers either side of the collapse. We are worried about that. There are possibilities of opening up an alternative 4-wheel drive access or a barge operation to take people across the river. They are being investigated, as well as the possibility of a complete new Bailey bridge.
Investigations will take at least 2 or 3 days, and we will err on the side of caution to make sure that we know what we are talking about. I have great faith that the department will not come up with a temporary fix that could create additional problems. We are working on it as fast as we possibly can. I realise that the member for Goyder, in whose electorate the bridge is located, will receive many telephone calls demanding a solution and I ask that people be patient.
We are fortunate that there is an alternative route through Pine Creek. Admittedly, it adds 2 or 3 hours to the journey, but we can still get into the area. Thank goodness we built the Kakadu Highway, the permanent road from Pine Creek, some years ago!
We will not proceed until we know absolutely that we have sound footings in the Adelaide River. It could cost at least $6m, I think, to replace the bridge completely, and we may have to do that. However, I await eagerly the geotechnical advice which is now being sought. I wish the engineers who are working on this project well, in the certainty that they will get on with it as fast as they can and come up with the best alternative access as well as the best method of repairing the damage.
ANSWER
Madam Speaker, this bridge is vital to Northern Territory communications and economic output. To have it out at any time is not good - especially for people who live or own property on the far side of the river.
Some 2 to 3 metres in the middle of the outbound lane sagged after a road train passed over the bridge. I do not place any blame on the road train. In fact, I want to thank the driver of that road train – and thank goodness it was not a passenger bus! In my opinion, the damage was not caused by the road train. However, the driver felt the bridge wobble and had the sense to pull up on the other side and call the police, and to stop other drivers from travelling across. I do not want to give the impression that any blame should be placed on the road train operator. I would be stunned if the vehicle was overloaded enough to do the damage that has occurred. I want to place that clearly on the record.
A preliminary structural check was undertaken last night by engineers from the department. It appears that a pile supporting the pier has settled into the foundation material. When the bridge was constructed in about 1972, a solid base was found for the bridge piles, but it appears that over time this pile has been forced through that material and there is no proper foundation underneath to support it. It is as if it has punched through a crust that had developed there, and gone to the bottom.
The problem is, what about the other piles of the bridge? Are they in the same state or was it just this one? The department is now drilling to try and find whether or not there is a solid foundation in the bed of the Adelaide River - one of the great rivers of Australia and, indeed, of the world. It is a very large river. Members will recall that, before the Arnhem Highway was constructed, travelers had to cross the river at the 47 Mile, the Marrakai crossing, a long way upstream from the present bridge.
We are flying in some experts to assist us in geotechnical analysis of the riverbed. Our problem is that a Bailey bridge over the span will put extra weight on the 2 piers either side of the collapse. We are worried about that. There are possibilities of opening up an alternative 4-wheel drive access or a barge operation to take people across the river. They are being investigated, as well as the possibility of a complete new Bailey bridge.
Investigations will take at least 2 or 3 days, and we will err on the side of caution to make sure that we know what we are talking about. I have great faith that the department will not come up with a temporary fix that could create additional problems. We are working on it as fast as we possibly can. I realise that the member for Goyder, in whose electorate the bridge is located, will receive many telephone calls demanding a solution and I ask that people be patient.
We are fortunate that there is an alternative route through Pine Creek. Admittedly, it adds 2 or 3 hours to the journey, but we can still get into the area. Thank goodness we built the Kakadu Highway, the permanent road from Pine Creek, some years ago!
We will not proceed until we know absolutely that we have sound footings in the Adelaide River. It could cost at least $6m, I think, to replace the bridge completely, and we may have to do that. However, I await eagerly the geotechnical advice which is now being sought. I wish the engineers who are working on this project well, in the certainty that they will get on with it as fast as they can and come up with the best alternative access as well as the best method of repairing the damage.
Last updated: 09 Aug 2016