Soil Vapour Assessment

Soil vapour assessment is the investigation of volatile contaminants (i.e. substances that easily evaporated at normal temperatures) present in soils, that pose a risk to human health when inhaled.

Volatile contaminants such as petroleum hydrocarbons and chlorinated solvents may be released to the subsurface environment through accidental spills, leaking of underground tanks and unregulated burial of contaminated wastes.

Modern buildings are designed to be energy efficient. This commonly includes a design which reduces air exchanges within the building and removal of a subfloor space to regulate temperature. Receptors within a building are at risk of being exposed to elevated levels of volatile contaminants, from a source which migrates from the subsurface to within a building, accumulating due to the low exchange of air. In addition to accumulation in buildings, volatile chemicals can collect in ambient air, confined spaces and excavations within a site.

Due to this, the correct design of an investigation is vital to undertaking a risk assessment that accurately characterises the actual risk present based on the type of contaminant present and its characteristics, the subsurface environment, migration pathways present and potential receptors within a site.

There are two soil vapour sampling methods, active and passive.

  1. Active sampling involves pumping or extracting a known volume of air from the sample location and collecting either a sample of gas into a TEDLAR Bag SUMMA Canister; or adsorbent media such as a carbon sorbent to. Active sampling methods usually provide results in the form of mass of contaminant per volume of air, as the exact volume of air extracted for analysis is measured.
  2. Passive sampling is based primarily on the principle of diffusion and measures the mass of contaminant that adsorbs to adsorbent media in the sample location over a period of time. Specifically, it involves the installation of an implant into the ground at depth (in the form of an adsorbent media) which would be recovered for analysis after an appropriate period of time (hours, days). When applied to soil gas, passive sampling is a semi-quantitative tool as it cannot provide concentration data, as the specific volume of air to pass through the media is unknown.

Whilst soil vapour can be modelled from groundwater and soil data, it is often overtly conservative. Incorrect or inadequate investigations can lead to an inaccurate determination of the risk present, response to address the perceived hazard including unwarranted engineering controls, delay of program and significant costs.

ADE has extensive experience in conducting soils vapour assessments, and implements a program of investigation which is accurate, efficient and cost-effective. Throughout the assessment process, ADE works closely with its client to ensure they are well informed about the potential hazards present, how to address any data gaps within the site, and the cost of remediation if required.

A.D. Envirotech Australia Pty Ltd – Head Office (NSW)
Unit 6/7 Millennium Ct.,
Silverwater, NSW, 2128, Australia
(02) 8541 7214

A.D. Envirotech Australia Pty Ltd – Laboratory (NSW)
4/10-11 Millennium Ct.,
Silverwater, NSW, 2128, Australia
(02) 9648 6669

A. D. Envirotech Australia Pty Ltd – (QLD)
PO Box 288 Upper Coomera LPO,
QLD, 4209 Australia
(07) 5519 4610

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