Groundwater Contamination Second Opinion

Situation: An underground storage tank breach at a Rosebery service station released petrol into the shallow groundwater that flowed under the neighbouring dry cleaning business and residential apartments. Around the time, residents complained to authorities about chemical odours within the apartments.

The authorities together with an environmental consulting firm investigated the odours and concluded they were caused by the petrol release. The service station was declared, “significantly contaminated”, under the Contaminated Land Management Act (1997) and remediation via long-term groundwater extraction and treatment was recommended. The service station owner was instructed to install an air extraction system below the neighbouring apartments. The service station owner engaged Geo-Logix for a second opinion.

Action:

• Geo-Logix reviewed the investigation report and found the data did not support the petrol release as the source of the odour complaints. They presented their rationale to the authorities and persuaded them to allow further investigation.
• Geo-Logix conducted subsurface soil-gas sampling beneath the residential units and indoor air sampling in the units. They also conducted offsite assessments of the soil and groundwater.
• Geo-Logix suspected the dry cleaner was the source of the odours. During operating hours the dry cleaner left the rear door open to ventilate the store. The door opened onto a pathway and the apartments had windows opening onto the pathway.
• Analysis of the soil-gas and indoor air samples failed to detect petroleum compounds but found dry cleaning compounds many times greater than human health-based screening levels.
• The service station owner was spared the expense of improving the air quality in the units and the expense of aggressive groundwater remediation.
• Geo-Logix conducted groundwater modelling to ascertain whether petroleum in the groundwater presented any human health or environmental risk.
• While authorities concurred that the groundwater could remain in place, they sought a reduction in the level of contaminants.
• Geo-Logix developed a remedial solution for injecting into the groundwater. The solution would feed the anaerobic microbes in the ground causing them to multiply and break down the petroleum (enhanced bioremediation).

Result: Geo-Logix’s remedial solution was far less expensive than commercially patented remedial solutions and could be easily mixed in the field and injected into the groundwater via groundwater monitoring bores.

The solution was injected intermittently over a period of six months. For two years the chemical concentrations in the groundwater were monitored quarterly. When the data was analysed it showed the groundwater contaminant plume was attenuating.

Geo-Logix presented the data to the authorities concluding the contamination did not present a risk to human health and the environment and could be left in place to attenuate over time. The authorities concurred and confirmed that no further regulation under the Contaminated Land Management Act (1997) was required.

If Geo-Logix had accepted the conclusions of the initial environmental studies, the service station owner would be extracting and treating groundwater to this day plus they would have had to install a costly air-extraction system.

The Geo-Logix philosophy is to understand the contamination risk before conducting remediation. Geo-Logix focuses on mitigating risk and not remediating for the sake of it.