When a leak was detected from an underground storage tank at a Jakarta gas station, Golder was engaged to investigate the extent of the contamination and the potential health risks to adjacent communities that depend on groundwater for domestic and potable use.
Through a quantitative assessment of health risk and by screening remedial options, we determined that the most efficient strategy was to extract soil vapour and groundwater to remove the maximum amount of contaminant. Residual contamination downgradient would be monitored for natural attenuation, offering the least disturbance to local communities.
After a pilot test of the selected technology, detailed feasibility and remedial action plans were submitted, and were subsequently approved by the regulators. Hazard and operability (HAZOP) and hazard identification (HAZID) studies provided safety parameters for the remedial design.
Our client engaged us as their environmental advisor to package the remediation project for tendering; however, the procurement process indicated that there were no engineering contractors with the capabilities to provide the service. Taking this into account, the client opted to engage Golder to build and operate the system. Using our global expertise, we designed and built the world-class system at our Montreal facility, and shipped it to our team in Indonesia for next steps.
Golder’s local team and contractors installed, commissioned, operated, maintained and monitored the remedial system. Significant cost savings and time efficiencies were achieved by having our local team handle the onsite preparations of 22 extraction wells for soil vapour and groundwater extraction and reinjection. Our presence on site also gave us in-depth knowledge of the site conditions so that we could improve the design and maximise the use of existing site facilities.
In one example of the system efficiencies achieved, we accounted for the marked changes in seasonal groundwater levels (exceeding 2 m) in the design and operating procedures by using the gas station’s pre-existing but inactive oil–water separators as buffer containment for extra loads during peak rainfall.
Using a local team led to enhanced relationships with residents and enabled periodic sampling of affected wells, as required by the monitoring program. Consistent regulatory liaison also strengthened our client’s reputation for responsible management of the incident.
The remediation process was a success, achieving the clean-up criteria and complying with all effluent, emissions, odor and noise limits.