What are Altona Properties' objectives?
What treatment options were examined?
Can the contamination be removed?
How are the contaminants being removed?
Will removing the contamination be dangerous to human health or the environment?
How long will it take to remove the contamination?
What groundwater treatment results have been achieved
Will the method of treatment change?
What contingency plans exist?
What monitoring will occur in the future?
Groundwater well treatment network.
The way forward.
How is the contaminated soil being treated?
How long will it take to treat the soil.

• What are Altona Properties' objectives?

The groundwater plume originates in areas of very high contamination or "hot-spots" located at the southern end of the Altona Plant. Contamination in the hot-spots is far too high for microbes to live, so there is no natural breakdown of contaminants

In December 1997, Australian Vinyls announced its intention to treat contamination at a meeting of the Altona Neighbourhood Consultative Group. From this announcement, objectives for treating the contamination were included in the Altona Plant's Environment Improvement Plan agreed between Australian Vinyls, community and the EPA in November 1998. These objectives are as follows:

We believe we can meet these objectives through the aim of removing contaminants from the dry rock and soil between the ground surface and the top of the upper aquifer, and also from the upper aquifer itself.

We plan to target our treatment of the contamination in the hot-spots. If we can reduce contaminant levels in these areas, the groundwater plume may reduce as microbes "eat" the remaining contaminants.

This treatment option was selected as the one which best met the criteria of effectiveness, duration, licensing certainty and cost.

• What treatment options were examined?

During 1997, we examined the following treatment options:

• Natural Degradation - involves no action except monitoring of contaminant concentrations in the groundwater. This method relies on natural breakdown of contaminants.

• Enhanced Natural Degradation - involves feeding the microbes to speed up natural degradation.

• Treatment of Hot-spots - targets highest contaminant concentrations for treatment thereby reducing the movement of contaminants into areas of lower contamination levels..

• Interception System - involves the removal of groundwater along various boundaries in order to prevent further off-site movement of the contamination.

• Groundwater Remediation - involves treatment of the entire groundwater plume, rather than concentration on the hotspots.

Each option was examined for the potential to remove any "pure" contaminants, limit the movement of dissolved contamination, net environmental benefit, likely time of operation, EPA requirements and whether the option would assist in restoring the suitability of the water for stock watering. The EPA has identified that this potential beneficial use for the groundwater needs to be protected.

• Can the contamination be removed?

• How were contaminants being removed and treated?

Air was being blown into the upper aquifer at each of the hot-spots. This rises through the groundwater and brings contaminants with it. The air blown in, and the contaminants it collects, were then removed from the dry rock above the aquifer with suction pumps. The contaminated air was then filtered to remove moisture and then oxidised in an above-ground treatment system.

• Was removing the contamination dangerous to human health or the environment?

The discharge of air from the treatment system was licensed by the EPA to ensure there were no impacts on people or the environment. The discharges were monitored to ensure compliance with the EPA licence.

• How long will it take to remove the contamination?

This is still unknown. The groundwater treatment system was  in operation from early 2001 until mid 2010, and was proven effective in removal of contaminants from groundwater at the site. A comparison of the extent of contamination in 1997 with the most recent monitoring data clearly shows a significant reduction in the amount of contamination at the site. See monitoring and treatment.

Currently, natural degradation of contamination is being closely monitored with ongoing groundwater monitoring allowing us to estimate the time for a full clean up. We will keep the Soil and Groundwater Review Group fully informed, and will provide the same information in future updates to this plan.

•What groundwater treatment results have been achieved

Please refer to Monitoring of Treatment for the most recent groundwater information.

• Will the method of treatment change?

If the methods we are using are not effective, we will discuss options with the Soil and Groundwater Review Group, and the appointed anvironmental auditor. See environmental audit for further details.

• What contingency plans exist?

Should adverse monitoring results be recorded or the treatment of 'hot-spots' have limited success a number of contingency and containment options have been established including: continued natural degradation and monitoring; installation of a treatment system across the extent of the contaminant plume; and installation of an interception system to prevent further off-site movement of the contaminant.

• What monitoring will occur in the future?

The existing groundwater monitoring programme will continue. Eventually we hope to reduce sampling frequency as the contamination levels decrease in response to action to eliminate the hotspots.

• Groundwater well treatment network

In September 2005 a review of air sparge performance found hot spot treatment was most effective around functioning air sparge wells, with contaminant trends declining and little evidence of rebound. Based on these findings, enhancements of the existing air sparge and soil vapour extraction well network to treat the remaining contaminant hot spots was recommended.

In April 2006 twelve new air sparge wells (to 16 metres depth) and seven new soil vapour extraction wells (to 8.5 metres depth) were drilled and installed. Locations of new wells target the dissolved-phase chlorinated hydrocarbons impacts in the upper basalt aquifer in the vicinity of the former EDC bund and along the southern site boundary.

There are now a total of seventeen air sparge wells and eighteen soil vapour extraction wells, which will be operated in phases to allow a more targeted approach to groundwater treatment.

• The way forward

Following shutdown of the treatment system a period of monitoring will be undertaken to measure the effect of natural attenuation on the level of contaminants and to measure how the contamination levels change over time. Recommendations for future treatment if necessary will be made on the back of this assessment.