3233 Soil vapour protocol for assessing hydrocarbon sites in the United Kingdom

Overview:

Human health risk assessment considers exposures to chemicals via a variety of exposure routes, including ingestion, dermal contact, and inhalation. For volatile organic chemicals (VOCs), inhalation is often of greatest concern, and vapour intrusion to indoor air is one of the possible inhalation routes. Assessing potential risks associated with this pathway is becoming increasingly common for land redevelopment and transfer, and contaminated land management. Experience has shown that these assessments can be challenging, in part due to an evolving knowledge base and tool set, and lack of practical guidance. 

This publication provides guidance to practitioners, regulators and other interested parties relating to the use of subsurface vapour monitoring as a component of a site characterisation and risk assessment, specifically for the purpose of evaluating subsurface vapour intrusion to indoor air.

The purpose of this document is to bridge the gap between:

• the historical ground gas sampling approaches that were employed to identify acute hazards and as tracking tools.
• the more recent need for high quality, contaminant-specific approaches required for vapour intrusion assessments.

This document provides information to foster a better understanding of the processes that control the nature and distribution of petroleum hydrocarbons along the vapour intrusion pathway. It describes the role of the conceptual site model in establishing data quality objectives. In identifying where to collect soil vapour samples, it recommends sampling techniques to promote data of high quality and integrity. Collectively, this information can be used with professional judgement to customise a soil vapour assessment to the site-specific conditions.