/// Monitoring of private bores continues /// Community liaison group

/// Community meeting

The Department of Defence, through its contractor Thales, is committed to the environmental clean-up at Mulwala. As part of this commitment, Defence has undertaken to analyse the water quality of private bores annually.

Water samples from the private bores are analysed and compared to the requirements in the Australian Drinking Water Guidelines.

Thales requires permission to enter your property each year, before undertaking bore testing. If you are going to be away from your home for an extended period during your test period, please contact the Thales environmental manager, to arrange an alternative time.

If your bore is not currently being tested and you would like it to be, or have any concerns about your bore testing, contact Thales’s environmental manager, Doug Wilson (03) 5742 2479.

A community liaison group was established in 2001 to liaise with Defence and Thales (previously ADI) about the management of the groundwater contamination. Originally there were seven community members in the group, but this has dwindled for a variety of reasons. If you would like to join, please contact Doug Wilson on (03) 5742 2479.

A community meeting has been scheduled for late 2010, once the final results of the hydraulic containment trial are available (see page 2). An update on the capping works will also be available.

The meeting will be held locally, at a date to be confirmed. The meeting will be advertised in the public notices of the Yarrawonga Chronicle two weeks prior.

You can find more information about the project on the Department of Defence website www.defence.gov.au/id/mulwala or call (02) 6266 8058.

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2010

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Environmental matters | Mulwala facility

Newsletter No.10, September 2010

In this edition, Thales provides a project update for the treatment of contaminated ground water in the Mulwala area, an overview of the hydraulic containment project, and details of the source area capping which will begin in late September.

The Department of Defence, through its contractor Thales, is committed to the environmental clean-up at Mulwala.

You can find more information about the project on the Department of Defence website www.defence.gov.au/id/mulwala or call (02) 6266 8058.

/// Contaminated groundwater management

The Contamination Management Plan presented to the community in 2006 identified the need to manage the contaminated groundwater in the Mulwala area. Investigations to determine the best way to remove contaminated water are continuing.

A hydraulic containment trial has recently been completed to determine if it is possible to significantly slow the movement of existing contaminated groundwater from beneath the facility by pumping from carefully located bores (see figure 1 below and the hydraulic containment article on page 2.)

A capping program will begin in late September (see article on page 3) to prevent further contamination. This will minimise the time taken for the groundwater beneath the community areas to return to background concentration levels.

The capping project will have little impact on the broader community, but residents whose properties back on to the redundant drain or live along Waratah road, will notice an increase in earthmoving equipment over a six week period.

Overall, the environmental remediation work at Mulwala is progressing well. So far, Defence has invested $4 million over the past eight years. Ongoing remediation work is likely to continue for the next five years to ensure Defence, through its contractor Thales, completes the environmental clean-up at Mulwala.

MurrayRiver

Wetland Sand dune

Shepparton (shallow) aquifer

Calivil (deep) aquifer

Clay

Floodplainaquifer

Old valley(‘trough’)

Bedrock

South West

Floodplain area

Facility

Sand dune area

North East

Figure 1: Simplified groundwater flow model (AECOM 2007)

www.defence.gov.au/id/mulwala 1

How was the trial undertaken?The trial was conducted by installing seven groundwater bores. Of these, four were used to extract water and three for monitoring groundwater levels.

What happened to the water after being extracted?The extracted bore water was treated with an on-site effluent treatment plant, before being discharged in to the Murray River. The treated water complies with the Mulwala facilities licence conditions granted by the Department of Environment Climate Change and Water (DECCW).

What information was collected from the trial?The data collected throughout the two month trial included:

• Bore water composition• Pumping rates• Static ground water levels• Soil bore logs.

Figure 2: Installation of an extraction well

/// Hydraulic containment trial successful

/// Source area capping program to begin shortly

A two month hydraulic containment trial has been successfully completed at the Mulwala Facility by environmental consultant, AECOM. The information collected will be used to decide if the extraction of groundwater is a suitable long-term strategy to treat contaminated groundwater. The results of the trial are expected to be available later this year.

What is a hydraulic containment trial?Hydraulic containment is an environmental remediation method used to capture, remove and treat contaminants in the groundwater. At Mulwala, this means capturing the contamination before it travels outside the facility boundary. Extraction wells were placed in peak contamination areas to achieve maximum results.

Figure 3: Automatic controlled pumping system Figure 4: Clay cap construction

Intercepted rain

Waste material

Topsoil/mulch & vegetation

Topsoil layerRun-off

Clay cap (sealing layer)

Surface water infiltrationrunoff over sealing layer

Intercepted rain

Evapotranspiration

START OF RAIN EVENT

Root-zone

Intercepted capacity exceeded

DURING RAIN EVENT

Shallow infiltration

AFTER RAIN EVENT

Water storage in soil

Figure 5: Phytoremediation cap

Intercepted rain

Waste material

Topsoil/mulch & vegetation

Topsoil layerRun-off

Clay cap (sealing layer)

Surface water infiltrationrunoff over sealing layer

Intercepted rain

Evapotranspiration

START OF RAIN EVENT

Root-zone

Intercepted capacity exceeded

DURING RAIN EVENT

Shallow infiltration

AFTER RAIN EVENT

Water storage in soil

Intercepted rain

Waste material

Topsoil/mulch & vegetation

Topsoil layerRun-off

Clay cap (sealing layer)

Surface water infiltrationrunoff over sealing layer

Intercepted rain

Evapotranspiration

START OF RAIN EVENT

Root-zone

Intercepted capacity exceeded

DURING RAIN EVENT

Shallow infiltration

AFTER RAIN EVENT

Water storage in soil

What is the objective of the source area capping?The objective of the capping is to return the land back to its natural state. The redundant drain which runs southwest from Bayly Street towards the Murray River flood plain will be returned to a Yellow Box Woodland.

What is source area capping?Source area capping is an environmental remediation method which covers the contamination with a non permeable layer to prevent further contamination. At Mulwala, two different methods will be used - clay capping (figure 4) and phytoremediation capping (figure 5) .

What are the differences between clay capping and phytoremediation capping?Clay capping prevents water from passing through. This stops further contamination travelling from the surface to underground water sources.

Phytoremediation caps allows water to travel through only the top layer of soil. Over time, this stored water is used by grasses and shrubs which allows the water to return to the atmosphere through the normal water cycle.

How is capping installed?Both capping methods are installed with earthmoving equipment, to place the material into the correct position for effective water management.

How will this affect me?The capping project will have little impact on the Mulwala community, as the majority of works will be within the boundary of the Thales Mulwala facility.

Residents who are near the redundant drain which runs southwest from Bayly Street towards the Murray River flood plain will notice an increase in earthmoving equipment required to undertake the capping works.

Residents who have properties along Waratah Road will have an increase of vehicular traffic through delivery of materials associated with the capping.

When will the capping occur?The capping is due to commence at the end of September, depending on weather conditions. The earthmoving equipment will be required for about six weeks.

Activity will only take place between 7 am – 6 pm on weekdays and between 8 am – 4 pm on the weekends.

How will the capping be tested?Environmental consultant, AECOM, will assess the quality of the groundwater and moisture infiltration every three months. The capping will be monitored for two years, before an assessment is made about how effective the capping has been.

How will the information be used?The information collected during the trial is being assessed to determine if the extraction of groundwater is a viable way to treat contaminated ground water in the medium to long-term.

When will the results be available?The final report is expected to be delivered in late October 2010. Once the results are available, a community meeting will be held (see Community Meeting article on page 4).

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