Introduction First Philippines Industrial Corporation (FPIC) owns an underground petroleum pipeline bringing refined petroleum products to a depot in MetroManila. In 2010, an accidental petroleum leak occurred in an underground section near a residential area. Health risk concerns to residents from petroleum vapour were raised. An environmental site assessment (ESA) done 2011 revealed a cemented layer composed of silty and sand material from 2.0 to 4.5 metres underground, acting as ‘vaportard,’ limiting upward vapour migration. Impacted groundwater and soil are situated below the vapor-tard, minimising vapour intrusion. As part of the remediation, ambient and indoor vapour intrusion studies have been conducted to determine exposure risks.
Methods Community ambient levels of volatile organic compounds (VOCs) and Benzene have been measured from 2011 to 2015. In 2011, vapour intrusion (VI) study was performed to assess potential indoor air impacts from subsurface vapour intrusion. Probes were installed through concrete floor slabs and sampled for vapours.
Result 99% of VOCs and 100% of Benzene ambient air readings are below the detection limit of the photoionization device. 1% of VOC readings ranged from 0.1 to 2.0 ppm. The VI study has detected 17 VOCs in indoor and vapour samples above screening levels. These VOCs in indoor air is not likely to be related to the VI pathway, and linked to background indoor and outdoor sources related to fuel products of combustion such as vehicle traffic from a major highway, asphalt paving, and cooking fuels.
Discussion Results show the ‘vaportard,’ layer is effective in limiting the upward migration of vapours from the underground release area. Monitored VOCs are from ambient air pollution with mobile sources as major contributor. No risk to health of residents was identified. Remediation is on-going and has achieved the Human Health Risk Assessment targets and is in the final stage of completion.
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