Background/Objectives. At thermal conductive heating (TCH) remediation sites, subsurface temperatures may exceed 100°C which dramatically increases chemical volatility, and therefore compounds may be present in extracted soil vapor which are not typically monitored with routine vapor analytical methods. Semi-volatile organic compounds (SVOCs) may be present in the vapor stream in significant concentrations and are often a crucial metric for tracking remedial progress in the form of mass removal. In addition, it may be necessary to monitor vapor discharge for unique site contaminants to ensure compliance with site specific air permits and/or health and safety concerns. Due to a lack of conventional EPA methods suited for soil vapor sampling and analysis of SVOCs, TerraTherm has directed and overseen the development of sampling methods and vapor phase testing for site specific volatile organic compounds (VOCs) and SVOCs. As part of this method development, consideration was given to all the unique challenges associated with thermal remediation projects, including high temperatures, very high moisture content, high and variable concentrations, and variable chemical composition over time. Durability and ease of use of the sampling equipment was also considered during method development, since many existing sampling techniques are not well suited for sampling process vapor. In addition to method development, TerraTherm has utilized modified existing EPA methods to suit the needs of thermal remediation projects.
Approach/Activities. Several case studies from non-standard VOC and SVOC thermal remediation sites will be reviewed: modification of existing method EPA TO-17 using thermal desorption tubes and sampling syringes for the sampling and analysis of diesel range organics in process vapor; applying a low volume polyurethane foam (PUF) sampling methodology (EPA TO-10A) coupled with existing method EPA TO-9A for sampling and analysis of dioxins in process vapor; method development for durable large capacity solid adsorbent tube for custom SVOC and pesticide analysis; and method development to demonstrate response and recovery of site specific SVOCs in canisters with existing method EPA TO-15. A review of the existing and potential means of measuring perfluoroalkyl substances (PFAS) in vapor will also be addressed, as this will be a consideration for PFAS remediation sites in the future.
Results/Lessons Learned. Moisture control during process vapor sampling is necessary if large (greater than several liters of air) sample volumes are collected. Viable moisture control approaches include choosing a sampling media which is not adversely affected by condensation/humidity, limiting the sample volume, or having a vapor conditioning step prior to the sampling media, Controlling moisture during sample collection will affect the sample composition, and TerraTherm has developed methods to account for this crucial step in sample collection. Investing the additional effort and money to perform method development before the start of a remedial program can help ensure success of the project. Clear and constant communication with the analytical laboratory is key when implementing any non-standard sampling program, and especially a process vapor sampling program where results are subsequently used to measure the progress and performance of the thermal remedy. Use of modified or non-standard vapor analytical methods can be an integral part of a thermal remediation project when semi-volatile compounds are present.