Morwell Land Movement
Lining of Morwell Main Drain
Following a series of meetings, geotechnical experts from the former Department of Primary Industries (DPI) and International Power Hazelwood (IPH) recently reached agreement on the liner system to be used on the Morwell Main Drain.
DPI has engaged Tim Sullivan to review geotechnical data gathered over the past 6 months and establish critical zones where the lining will be installed in full. This information will be used to finalise the drain design.
Mr Sullivan is an eminent geotechnical consultant on slope stability for some of the world’s largest mining operations.
Based on the information currently at hand, final design work is expected to be completed by the end of August. IPH will then undertake preliminary work and ordering of materials. Construction work is planned to commence on 1 November, weather permitting.
The installation of the liner will assist with the prevention of sinkhole formation in the drain and prevent water from flowing into cracks in the coal, thereby reducing slope instability.
Land Movement Survey
DPI has completed a Land Movement Survey of cracks in an area to the south of the Morwell township, closest to the Hazelwood Mine.
Many residents were kind enough to allow DPI technical officers access to their private property for the purpose of observing and recording cracking.
The survey found cracking all over the survey area but the most significant was within the tennis courts near the corner of Hazelwood Road and Wallace Street. The survey cannot tell us the specific reason for the cracking that has occurred. Rather, it was commissioned it as a reference survey that will be used for comparison in future, so that any changes in the cracking can be tracked.
A summary version of the survey, with photographs of private properties removed to ensure privacy, is available on this site.
Following a heavy rainfall event on 5 February 2011 small but significant movement occurred in the northern wall of the Hazelwood Mine. As a result of the movement, cracks appeared on the surface of the Princes Freeway and the adjoining area. A section of the Princes Freeway running between the mine and the township of Morwell was temporarily closed.
DPI arranged for the Chair of the Technical Review Board and other geotechnical experts to review the incident and provide advice on remedial works required to ensure that the area was stabilised to ensure public safety and ultimately for the freeway to be re-opened.
On 21 September 2011, the Princes Freeway was re-opened, following the completion of an extensive remedial works program.
For further information, see the August 2011 Public Information Session Presentation
Who Led the Response to the Event?
The Government formed an Emergency Management Team led by VicPol and including DPI, VicRoads, Latrobe City Council and International Power. DPI continues to work closely with all relevant agencies to ensure public safety and to keep the community and all relevant stakeholders informed of all recovery actions.
A stakeholder group was established to provide a co-ordinated response to the event led by the VicPol Incident Controller. This group has carried out a detailed analysis of the situation and put emergency measures in place.
An inter-departmental committee was also established to coordinate a whole-of-government approach to address the complex issues arising from the movement of the north wall of the Hazelwood mine.
What Is DPI’s Role?
DPI is the regulator for mining and extractive industries in Victoria, and is overseeing mitigation works undertaken by IPH (who own and operate the Hazelwood Mine), LaTrobe City Council and VicRoads in an effort to reduce the risk of further land movement.
DPI led the geotechnical and hydrological aspects of investigations into the stability of the Princes Freeway at Morwell and the adjacent Hazelwood mine wall and drew on the advice of a range of technical experts on the best way to ensure the long-term stability of the area surrounding the road.
DPI continues to provide expert technical advice to other agencies and oversee remedial work carried out by International Power.
What Action Is DPI Managing?
DPI is working closely with IPH, the local council and VicRoads. A number of recovery activities are well underway:
- A Quantitative Risk Assessment has been developed to inform decision making on what conditions are necessary for the road to be reopened.
- A review of remedial works and resultant risks was completed as the basis for re-opening the bypass.
- The Government has committed $2m to assist IPH begin work to remediate the main drain which passes through the area of instability.
- IPH and DPI have been working to reach agreement on the exact design and specifications of drain remediation.
- An extensive system of water level and ground movement observation points have been set up both inside and outside the mine to monitor ground conditions.
- A land movement survey of the residential area adjacent to the site has been completed.
- The drilling of 50 horizontal drain holes by IPH to release water from the area of instability has been completed.
- Real-time monitoring to immediately identify any further movement has been installed both at the freeway and within the mine.
- Two independent reviews have been completed - a review of public safety issues and a peer review of all technical advice received.
- A feasibility study has been completed by IPH into further earthworks and other remedial works to limit longer term movement at the site.
- A scenario workshop to establish and manage protocols for any emergency situation has taken place.
- An aerial survey of the affected area has been undertaken.
- IPH has commenced remedial works on the Northern Batters surface drainage system, which will better manage surface water within the batters.
What Happens Next?
VicRoads has lined the 300 metre central median along the currently closed section of the freeway; and other strengthening works including injecting grout into underground holes has taken place.
The monitoring of ground movement around the freeway area will continue.
Around the clock monitoring of the freeway will detect any change which may result in the need for a temporary closure in the future