Overview of state approaches to vapor intrusion: 2018

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.     

Disinfection and dewatering of wastewater solids by interstitial vapor generation.

Disinfection of wastewater solids (waste activated solids [WAS]) by interstitial vapor generation was investigated. In addition to the magnitude of disinfection, the amount of water removed and cost relative to traditional residuals disinfection processes was also examined. The process of interstitial vapor generation occurs as a result of the rapid heating of liquid in the interstices of the solid-liquid array. Intense heating causes boiling of the slurry liquid, resulting in an expanding vapor front that simultaneously dewaters the wastewater solids and contributes to the destruction of viable pathogenic microorganisms. Objectives of the study were threefold: (1) to validate disinfection of WAS using the interstitial vapor technique; (2) establish the degree of possible drying of the residuals using the techniques; and (3) establish the key operating variables for the process. Results showed a significant reduction in the most probable number of total coliforms and Escherichia coli (E. coli). Specifically, greater than four-log unit reductions were produced for both total coliform and E. coli bacteria. In addition to quantifying the reduction in bacteria, the percent solids were increased from an initial amount of 7.6% (mass basis) to a final solids content greater than 90% using optimal processing conditions. Cost comparisons were also conducted and shown to be quite favorable when compared with traditional disinfection methods such as lime addition. Because of the high level of E. coli reduction achieved, the process of interstitial vapor generation is shown to be capable of converting a class B biosolids into a class A pathogen reduced product. For example, an initial most probable number (MPN) of 1.2 x 10(6) E. coli bacteria were reduced to 19 at the extreme conditions of the process, well below the requirement of an MPN of 1000 for fecal coliform bacteria. Given its ability to disinfect and dewater wastewater solids, the interstitial vapor generation process was found to be a robust and beneficial technique to produce an environmental and publicly acceptable recyclable biosolids resource.     

On-Site Gas Chromatography/Mass Spectrometry (GC/MS) Analysis to Streamline Vapor Intrusion Investigations

Distinguishing between vapor intrusion and indoor sources of volatile organic compounds (VOCs) is a significant challenge in conventional vapor intrusion assessments. For this research project, the authors developed a step-by-step protocol to streamline building-specific investigations by using on-site gas chromatography/mass spectrometry (GC/MS) analysis and building pressure manipulation to determine the source of VOCs in indoor air during a 1-day field investigation. Protocol validation included implementation in industrial buildings and testing alongside conventional methods. The new protocol compares favorably to conventional approaches, yielding more definitive results in less time. This article presents three case studies which illustrate application of the protocol.     

Carrots and Sticks: New Brunswick and Maine Forest Landowner Perceptions Toward Incentives and Regulations

The governments of countries that allow private land ownership have two main tools to motivate landowner behavior: regulations and incentives. This research examines landowner preferences toward these policy tools and asks specifically: Do private forest landowners in New Brunswick and Maine believe that regulations and/or incentives are effective means to motivate responsible stewardship? Can landowners identify explicit regulations and policies that restrict property rights? Also, we were interested to see if any discernible differences existed between these adjacent jurisdictions from different countries, but that share similar forests and a similar settlement history. We identified and interviewed diverse landowners, recorded and transcribed our discussions, and analyzed the results using a grounded theory approach. Findings suggest that both New Brunswick and Maine participants are fairly comfortable with most regulations and many agreed that a combination of incentives and regulations are in fact useful. Furthermore, landowners in New Brunswick discussed non-monetary incentives as a mechanism to reward “good” stewardship; while Maine respondents articulated a degree of responsible stewardship that transcends a need to incentivize landowners. This study demonstrates that diverse landowners may be more comfortable with environmental regulations than previously understood and may be interested in non-monetary incentives.     

Capturing Old-Growth Values for Use in Forest Decision-Making

Old-growth forests have declined significantly across the world. Decisions related to old growth are often mired in challenges of value diversity, conflict, data gaps, and resource pressures. This article describes old-growth values of citizens and groups in Nova Scotia, Canada, for integration in sustainable forest management (SFM) decision-making. The study is based on data from 76 research subjects who participated in nine field trips to forest stands. Research subjects were drawn from Aboriginal groups, environmental organizations, forestry professionals, and rural and urban publics. Diaries, group discussions, and rating sheets were used to elicit information during the field trips. Findings show that different elicitation techniques can influence the articulation of intensity with which some values are held. In addition, certain values are more often associated with old-growth than with other forest-age classes. Some values associated with old-growth are considered more important than others, and some silvicultural treatments are perceived to compromise old-growth values more than others. Demographic characteristics, such as constituency group, gender, and age, are shown to influence value priorities. Ideas on how to incorporate old-growth values into SFM decision-making are highlighted.     

Overview of state approaches to vapor intrusion

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. © 2012 Wiley Periodicals, Inc.