A Practical Guide for the Measurement of Indoor Air Impacts from Subsurface Contamination

摘要

The USEPA draft Guidance documents for assessing potential exposure to occupants in structures over subsurface sources and contaminated soil gas plumes includes indoor and outdoor ambient air testing as a Tier 3 technology. Designing and implementing a formal ambient air program for this application, which includes attempting to assess potentially low-level impacts to indoor air quality as compared to outdoor air quality, can present a significant challenge. The purpose of this paper is present a practical guide to designing an indoor/outdoor ambient air program tailored for this particular application. Key design features of a proper program will be included, such as: QA guidance, selection of target species, selection of sample collection and analytical methods, detection limit expectations, monitoring design including number of stations and frequency of sample collection, and data qualification and use. For many sites with common subsurface contamination, this process can be greatly simplified to a practical guidance. As such, basic air monitoring protocols will be provided for two common scenarios, including potential exposure to chlorinated compounds found in the subsurface soil gas, and potential exposure to compounds found in petroleum product releases. Simple but effective air sampling programs will be provided and discussed for two levels of effort, screening-level, and in-depth level assessment.