The most common disposal method in the United States for municipal solid waste (MSW) is burial in landfills. Until recently, air emissions from these landfills were not regulated. Under the New Source Performance Standards and Emission Guidelines for MSW landfills, MSW operators are required to determine the nonmethane organic gas generation rate of their landfill through modeling and/or measurements. This paper summarizes speciated nonmethane organic compound (NMOC) measurement data collected during an intensive, short-term field program. Over 250 separate landfill gas samples were collected from emission sources at the Fresh Kills landfill in New York City and analyzed for approximately 150 different analytes. The average total NMOC value for the landfill was 438 ppmv (as hexane) versus the regulatory default value of 4000 ppmv (as hexane). Over 70 individual volatile organic compounds (VOCs) were detected and quantified in the landfill gas samples. The typical gas composition for this landfill was determined as well as estimates of the spatial, temporal, and measurement variability in the gas composition. The data for NMOC show that the gas composition within the landfill is equivalent to the composition of the gas exiting the landfill through passive vents and through the soil cover.

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Many cross-sectional studies have been published where the levels of volatile organic compounds (VOCs) were measured in indoor air at one or two locations for houses or offices. This study provides longitudinal data for a commercial retail building and also addresses spatial variability within the building. The data suggest that spatial and temporal variability are important considerations for compounds emitted from indoor sources. Elevated concentrations were found in retail spaces with no apparent emission sources due to their proximity to other retail spaces with emission sources.

Our understanding of vapor intrusion has evolved rapidly since the discovery of the first high profile vapor intrusion sites in the late 1990s and early 2000s. Research efforts and field investigations have improved our understanding of vapor intrusion processes including the role of preferential pathways and natural barriers to vapor intrusion. This review paper addresses recent developments in the regulatory framework and conceptual model for vapor intrusion. In addition, a number of innovative investigation methods are discussed.

There has been a great deal of recent interest in evaluating the potential for vapor transport from subsurface contamination into nearby buildings. There does not exist, however, any method for calculating whether buildings that are not directly over the source of contamination may be impacted. For simplicity, typical modeling approaches for estimating vapor migration through soil into buildings assume that the contaminated plume or soil lies directly underneath the building. The models do not take into account the lateral distance, if any, between the source of VOC emissions and the indoor space. This paper presents an approach to calculate diffusion-limited emission fluxes as a function of lateral distance and evaluates the significance of these emissions over relatively short lateral distances from the source. A theoretical, mathematical approach was used. The results show that soilgas concentration and emission flux are both a decreasing exponential function of the lateral distance from the edge of the contaminant plume. Based on our calculations, the emission flux and the soil-gas concentration are insignificant within a relatively short lateral distance from the source (e.g., 30 m).

A large number of states have issued guidance addressing the vapor intrusion pathway making it difficult to keep up with various policies and requirements. We have compiled and reviewed guidance from 35 states, half of which have issued documents within the last three years. A comparison of policies among states shows reasonable consistency in some areas-for example, 20 of 23 states that provide an exclusion distance for subsurface sources of chlorinated volatile organic compounds (VOCs) use a distance of 100 feet. However, more commonly, the policy decisions vary widely. Among states, indoor air screening concentrations for the same VOC vary by more than 2,000 times and subsurface screening concentrations vary by more than 2,000,000 times. These wide discrepancies suggest a need for communication and consensus building in order to increase consistency in the management of the vapor intrusion pathway. O

Regulatory requirements for the evaluation of vapor intrusion vary significantly among states. For site owners and responsible parties that have sites in different regulatory jurisdictions, one challenge is to know and understand how the requirements or expectations for vapor intrusion differ from one jurisdiction to the next. Differences in requirements can make it difficult to manage sites in a consistent manner across jurisdictions. Eklund, Folkes, et al. (2007, February, Environmental Manager, 10–14) published an overview of state guidance for vapor intrusion in 2007 that provided a detailed summary of pathway screening values and other key vapor intrusion policies. An update by Eklund, Beckley, et al. (2012, Remediation, 22, 7–20) was published in 2012, which expanded the evaluation to additional states. Since that time, numerous states have substantially revised their guidance and some states that did not have vapor intrusion‐specific guidance have issued new guidance. This article provides an update to the 2012 study. For each state, the review includes tabulations of the types of screening values included (e.g., groundwater, soil, soil gas, indoor air) and the screening values for selected chemicals that commonly drive vapor intrusion investigations (i.e., trichloroethylene [TCE], tetrachloroethylene, and benzene) along with other compounds of potential interest. In addition, for each state, the article summarizes a number of key policy decisions that are important for the investigation of vapor intrusion including: distance screening criteria, default subsurface to indoor air attenuation factors, mitigation criteria, and policies for evaluation of short‐term TCE exposure.

The emission flux (masdtime-area) of tritiated water from TA-54 was measured to support the characterization of radioactive air emissions from waste sites for the Radioactive Air Emissions Management (RAEM) program and for the Area G Performance Assessment. Measurements were made at over 180 locations during the summers of 1993 and 1994, including randomly selected locations across Area G, three suspected areas of contamination at Area G, and the property surrounding TA-54. The emission fluxes of radon were measured at six locations and volatile organic compounds (VOCs) at 30 locations. Monitoring was performed at each location over a several-hour period using the U.S. EPA flux chamber approach. Separate samples for tritiated water, radon, and VOCs were collected and analyzed in off-site laboratories. The measured tritiated water emission fluxes varied over several orders of magnitude, from background levels of about 3 pCi/m2-min to 9.69~10~ pCi/m2-min near a disposal shaft. Low levels of tritiated water were found to have migrated into Pajarito Canyon, directly south of Area G. The tritium flux data were used to generate an estimated annual emission rate of 14 Curies/yr for all of Area G, with the majority of this activity being emitted from relatively small areas adjacent to several disposal shafts. The estimated total annual release is less than 1% of the total tritium release from all LANL in 1992 and results in a negligible off-site dose. Based on the limited data available, the average emission flux of radon from Area G is estimated to be 8.1 pCi/m2-min. The measured emission fluxes of VOCs were < 100 pg/m2-min, which is small compared with fluxes typically measured at hazardous waste landfills. The air quality impacts of these releases were evaluated in a separate report. iv Radian Corporation I 1.3 Obiectives This study is being performed for several reasons: e 'Emissions data are needed to support the Radioactive Air Emissions Management (RAEM) program's characterization of radioactive air emissions from waste sites to assure compliance with the National Emission Standards for Hazardous Air Pollutants (NESHAP) for radionuclides. e Although not a regulatory requirement, there is a need to characterize non-radioactive air emissions to determine if the Laboratory's waste operations are releasing toxic amounts of pollutants. e The Department of Energy (DOE) requires that all facilities follow Best Management Practices (BMP) with regards to all of their activities. Quantifying releases of pollutants, even though not required by regulators, is a BMP. The specific objectives of the test program were to: e Measure the emission flux (masdtime-area) of tritium, VOCs, and radon at a series of twenty points across Area G; e Measure the emission flux of tritium at a series of points in and around Area G where relatively high levels of tritium are suspected (Le., ''hot spots"); e Measure the emission flux of tritium at 20 locations and the emission flux Radian Corporation 1-3-_ I _ _ _-'Replaced point TR1-29 specified...