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What’s Acceptable for Soil Gas Analysis? BY BART SIMMONS, Ph.D. Soil gas analysis has been established as a powerful cost-effective technique for finding and defining soil and groundwater contamination. Many studies have documented the limitations of sampling soil for assessing contamination with volatile organics, and soil gas analysis provides a near-real-time alternative. Analysis of soil gas can also save costs for installation of groundwater monitoring wells. However, since soil gas analysis is not based in a traditional laboratory, it has fallen outside the realm of standard methods and normal quality systems standards. The Los Angeles Regional Water Quality Control Board, recognizing the importance of standardized analysis, established “Interim Guidance for Active Soil Gas Investigation,”which established detailed specifications for survey design, calibration and analysis. However, there are no widely-accepted soil gas methods. Passive soil gas has also proven to be cost-effective for site assessment; sorbents made of charcoal or Tenaxª can be buried at shallow depths, recovered, desorbed, and analyzed to provide detailed profiles of soil and/or water contamination. The Environmental Laboratory Accreditation Program (ELAP) in the Department of Health Services, does not have a Field of Testing for soil gas analysis. Because of the desire to include it in the accreditation program, a compromise has been established, in which ELAP will certify a mobile laboratory for the analysis of volatile organics using water methods, but will not certify the soil gas sampling methods. The need for soil gas standards is a high priority. Marcia Davies, who is a member of the Board of Directors for the National Environmental Laboratory Accreditation Conference (NELAC) and is head of the Hazardous, Toxic, and Radioactive Waste program for the Army Corps of Engineers, has identified soil gas analysis as a priority for NELAC field standards. NELAC is planning to expand its standards to include field analysis not done in a fixed laboratory; NELAC membership will be voting on the issue at the annual NELAC meeting in San Antonio in July. It is proposed that NELAC create a standing committee on Sampling and Field Measurements, which could propose standards on techniques like soil gas measurement. Like many field methods, soil gas analysis uses methods
which are not included in the usual Environmental Protection Agency (EPA) compendia of approved methods. EPA has
announced its intent to establish a Performance-Based Measurement System (PBMS), which could provide the flexibility
needed for soil-gas analysis and other field measurements. EPA program representatives recently reached agreement
on the language of a PBMS standard; the proposal was to be included as an appendix to the NELAC Quality Systems
standards by mid-April. The proposed changes to the NELAC standards can be downloaded from the NELAC web site at: Soil gas analysis, both passive and active, is an established technique for site assessment. Uniform national standards for these techniques will require more flexibility than existing lab certification allows; NELAC standards and the emerging PBMS will provide an opportunity for consistent and flexible standards. Comments to this column are welcome. Bart can be reached at: bsimmons@ix.netcom.com or you can send comments to the editor at: editor@grac.org Bart Simmons, Ph.D., is the Chief of the Hazardous Material Laboratory, Department of Toxic Substances Control, Berkeley, CA. |