Evidence of a sewer vapor transport pathway at the USEPA vapor intrusion research duplex (original) (raw)
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The Science of the total environment, 2018
Sewer systems have been recently recognized as potentially important exposure pathways to consider during vapor intrusion assessments; however, this pathway has not been well-characterized and there is need for additional information about the occurrence of volatile organic compounds (VOCs) in sewer systems. This paper reports the results of sewer gas sampling conducted in a sanitary sewer over the years of 2014-2017. Sewer gas samples were collected and analyzed using several different techniques, including TO-15 (grab), TO-17 (passive), Radiello® (passive) and a novel continuous monitoring technique, the Autonomous Rugged Optical Multigas Analyzer (AROMA). The applicability of each of the different approaches used in this study is discussed in the context of investigating sanitary sewers as a vapor intrusion alternative pathway. The data confirmed that trichloroethylene (TCE) concentrations in sewer gas were detected adjacent to and extending hundreds of feet away from a previousl...
A conceptual model for vapor intrusion from groundwater through sewer lines
Science of The Total Environment, 2019
chloroform, benzene, and tetrachloroethylene, are commonly detected in background sewer vapors. • Sites at higher risk for sewer VI are those with direct interaction between sewers and contaminated groundwater. • At direct interaction sites, median VOC attenuation was 80× from groundwater to sewer vapor, versus 7,900× at other sites. • Within sewer lines, VOCs attenuate away from the source usually with N80% concentration decrease over a distance of 500 ft. • At buildings impacted by sewer VI, 40 to 50× attenuation was seen between VOCs in the sewer line and the building.
Environmental Research, 1986
Simultaneous monitoring of the vapors in several sewer headspaces by three directreading instruments, the Century OVA flame ionization detector, a 10.2 eV H-Nu Photoionization Detector, and a Hydrogen Sulfide Ecolyzer revealed that the majority of condensable organic vapors in areas of the Metropolitan Sewer District of Cincinnati appeared to be saturated aliphatic organics, except during short, unpredictable episodes. The monitoring was performed in the wet well of a sewage treatment plant, in sewers near two chemical plants, and in three other different sewers. The approach outlined in this paper does not require the use of gas chromatography-mass spectrometry (GC-MS) analysis.
Water, Air, & Soil Pollution, 2014
A gas-phase tracer test (GTT) was conducted at a landfill in Tucson, AZ, to help elucidate the impact of landfill gas generation on the transport and fate of chlorinated aliphatic volatile organic contaminants (VOCs). Sulfur hexafluoride (SF 6) was used as the non-reactive gas tracer. Gas samples were collected from a multiport monitoring well located 15.2 m from the injection well, and analyzed for SF 6 , CH 4 , CO 2 , and VOCs. The travel times determined for SF 6 from the tracer test are approximately two to ten times smaller than estimated travel times that incorporate transport by only gas-phase diffusion. In addition, significant concentrations of CH 4 and CO 2 were measured, indicating production of landfill gas. Based on these results, it is hypothesized that the enhanced rates of transport observed for SF 6 are caused by advective transport associated with landfill gas generation. The rates of transport varied vertically, which is attributed to multiple factors including spatial variability of water content, refuse mass, refuse permeability, and gas generation.
Vapor intrusion in urban settings: effect of foundation features and source location
Procedia Environmental Sciences, 2011
In many urban settings, groundwater contains volatile organic compounds, such as tricholoroethene, tetrachloroethene, benzene, etc., at concentrations that are at or slightly below non-potable groundwater standards. Some non-potable groundwater standards do not protect against human health risks that might result from vapor intrusion. Vapor intrusion is a process by which vapor phase contaminants present in the subsurface migrate through the soil and ultimately enter a building through foundation cracks. The end result is a decrease in air quality within the building. Predicting whether or not vapor intrusion will occur at rates sufficient to cause health risks is extremely difficult and depends on many factors. In many cities, a wide-range of property uses take place over a relatively small area. For instance, schools, commercial buildings and residential buildings may all reside within a few city blocks. Most conceptual site models assume the ground surface is open to the atmosphere (i.e. green space); however the effect that an impervious surface (e.g. paving) may have on vapor transport rates is not routinely considered. Using a 3-D computational fluid dynamics model, we are investigating how the presence of impervious surfaces affects vapor intrusion rates. To complement our modelling efforts, we are in the initial stages of conducting a field study in a neighborhood where vapor intrusion is occurring.
2001
This study focuses on the status of the vadose zone remediation along 1600 ft of the process sewer line between the M-Area security fence and the M-Area settling basin. Three soil vapor extraction (SVE) units 782-5M, 782-7M, and 782-8M, connected to 4 vertical wells and 3 horizontal wells have been addressing the vadose zone volatile organic contamination (VOC) since 1995. The specific objectives of this study were to obtain soil gas and sediment samples, evaluate SVE units and vadose zone remediation, and make recommendations to address further remediation needs.
Contribution of domestic effluents to hydrocarbon levels of dry weather flow in combined sewers
Urban Water Journal, 2006
The importance of hydrocarbon contamination of the sewer network has been reported by many authors recently. Most of the studies are focused on the introduction of such pollutants into combined sewers by street and roof stormwater, but few evaluate the contribution of domestic inputs to hydrocarbon pollution. As a consequence, this workcarried out on the framework of the OPUR (Observatory of Urban Pollutants) research program-assesses the resolved aliphatic (AH), unresolved complex mixture (UCM) and polycyclic aromatic hydrocarbon (PAH) concentrations of domestic effluents (DE) and evaluates the role played by such effluents on the hydrocarbon levels of dry weather flow (DWF) in combined sewers. Results show hydrocarbon concentrations in the 200 -300 mg Á l 71 , 300 -1 000 mg Á l 71 and 0.9 -1.4 mg Á l 71 ranges for AHs, UCM and the 16 PAHs of the US-EPA, respectively. The assessment of hydrocarbon fluxes conveyed by domestic effluents on the scale of the 'Le Marais' experimental urban catchment (42 ha, centre of Paris) reveals the predominant contribution of domestic inputs to the DWF pollution and highlights the unsuspected role of households.
Vapor Intrusion Investigations and Decision-Making: A Critical Review
Environmental Science & Technology, 2020
At sites impacted by volatile organic compounds (VOCs), vapor intrusion (VI) is the pathway with the greatest potential to result in actual human exposure. Since sites with VI were first widely publicized in late 1990s, the scientific understanding of VI has evolved considerably. The VI conceptual model has been extended beyond relatively simple scenarios to include nuances such as biological and hydrogeological factors that may limit the potential for VI and alternative pathways such as preferential pathways and direct building contact/infiltration that may enhance VI in some cases. Regulatory guidance documents typically recommend initial concentration-or distance-based screening to evaluate whether VI may be a concern, followed by a multiple-lines-of-evidence (MLE) investigation approach for sites that do not screen out. These recommendations for detailed evaluation of VI currently focus on monitoring of VOC concentrations in groundwater, soil gas, and indoor air and can be supplemented by other lines of evidence. In this paper, we summarize key elements important to VI site characterization, provide the status and current understanding, and highlight data interpretation challenges as well as innovative tools developed to help overcome the challenges. Although there have been significant advances in the understanding of VI in the past 20 years, limitations and knowledge gaps in screening, investigation methods, and modeling approaches still exist. Potential areas for further research include improved initial screening methods that account for the site-specific role of barriers, improved understanding of preferential pathways, and systematic study of buildings and infrastructure other than single-family residences.