The Pennsylvania Department of Environmental Protection (PADEP) Land Recycling Program released revisions to the Technical Guidance Manual for Vapor Intrusion into Buildings from Groundwater and Soil under Act 2 on November 19, 2016; the new guidance will be effective January 18, 2017. After the initial presentations by PADEP, PennJersey Environmental Consulting has reviewed the new guidance in detail. While both agencies expect environmental professionals to use professional judgment, there are notable differences between the PADEP guidance and the New Jersey Department of Environmental Protection (NJDEP) Vapor Intrusion Technical Guidance, version 4.0, that are worth discussing in terms of the policies and science.
- PADEP allows an interim modeling step to calculate potential indoor air concentrations from the sub-slab or near slab soil gas data and conservative attenuation factors. These modeling options include the Johnson and Ettinger model or the American Petroleum Institute’s BioVapor for petroleum releases. NJDEP’s guidance states that soil gas data should be compared to the applicable soil gas screening level but allows the development of site-specific soil gas screening levels using the Johnson and Ettinger model based on site-specific factors not reflected in the default screening levels.
- As with the rest of the PADEP Land Recycling Program, use of a human health risk assessment is permitted to develop site-specific standards for vapor intrusion, including the use of a 10-4 cumulative cancer risk factor and a hazard index of 1. NJDEP allows human health risk assessment only in limited circumstances as specified in the Remediation Standards (N.J.A.C. 7:26D); modification of the toxicity data using less than a 10-6 cancer risk for individual compounds, as well as the 10-4 cumulative risk, is not allowed.
- Instead of the calendar-based “heating season” from November 1 – March 31 used by NJDEP for the collection of indoor air samples under a worst case condition, PADEP uses a temperature differential of 15 °F between the minimum indoor air and average outdoor temperature as the criterion for collecting indoor air data. Moreover, PADEP states that “If a building is not heated, then indoor air samples collected at any time of the year may be used for screening.” Investigators based in NJ have encountered data rejection if indoor air samples were collected as little as one week outside of the heating season, even if the weather dictated that the building was being heated and generating a stack effect. Alternatively, weather during the heating season may be warm enough that heating is not required during the day, and that windows are opened for ventilation – resulting in additional dilution of the indoor air and a low bias to the data compared to colder weather.
- PADEP allows mitigation to be performed at any time in the process in lieu of sampling and a complete evaluation of the VI pathway. Current or future plans for use of the inhabited building will determine the need for VI pathway evaluation. NJDEP allows the installation of mitigation systems using the assumption that the VI pathway is completed and requires mitigation; however, the investigator must report an Immediate Environmental Concern (IEC) and follow the regulatory and guidance provisions related to IECs. To avoid the “voluntary” IEC designation, the investigator would need to conduct the required receptor evaluation and collect sub-surface soil gas and indoor air samples to complete the receptor evaluation and prove that the mitigation is protective.
- PADEP’s guidance states that soils are a potential VI source in the unsaturated zone when they exceed statewide health standard screening values within specified distances to an occupied structure. NJDEP’s soil remediation standards include inhalation as a direct contact pathway; however, NJDEP’s VI guidance is clear that remediation standards should not be utilized because the standards were not developed for the VI pathway. NJDEP’s guidance states that the use of professional judgment should consider the volatile contaminant concentrations in soil, the proximity of the occupied structures, the biodegradation rate of the compounds, and the ultimate remedy, e.g., excavation, in situ treatment or other approaches.
- PADEP’s guidance states that crawl spaces are not regarded as occupied space. NJDEP considers a crawl space as a potentially occupied space and subject to the indoor air screening levels, even though crawl spaces are not occupied.
- PADEP has developed guidelines for activity and use limitations (AULs) to maintain the attainment of the statewide health standard. At present, there is not a specific deed notice (institutional control) or Remedial Action Permit in NJDEP’s program to address long-term vapor intrusion issues.
- PADEP recognizes the variability in indoor air data and allows the collection of multiple indoor air samples to determine compliance, stating that the “…two sampling events should occur at least 45 days apart for statistical independence.” In discussing this with PADEP, when multiple samples are collected, there should be a statistical evaluation supporting compliance; that is, a trend, or for larger data sets, the 75%/10x test or the 95th percent upper confidence level of the mean. Despite specific compliance and attainment guidance that allows compliance averaging of soil and groundwater data for comparison with the Soil Remediation Standards and Ground Water Quality Standards, NJDEP’s VI guidance states that “The results cannot be averaged for comparison to the appropriate screening level.” NJDEP’s prohibition extends to both spatial averaging on one or more dates and the averaging of the same sample location on different dates. NJDEP’s prohibition of averaging flies in the face of the scientific evidence, demonstrating the variability of indoor air concentrations. In his seminal study of indoor air levels of trichloroethene, Johnson concluded that the data varied by three orders of magnitude and that decision making based on a single point sample datum subjected the decision maker to the potential for false positives (taking action when the true aggregated exposure does not exceed the screening level) or, worse, a false negative (where the true aggregated exposure exceeds the applicable screening level). As an LSRP, the latter is inappropriate even if the standard of care as specified by NJDEP’s guidance has been met.
To paraphrase W.C. Fields, this is a situation where, all in all, I’d rather be in Pennsylvania. More seriously, I am tempted to substitute the PADEP guidance for NJDEP’s because there are more options to use the current science to assess potential vapor issues. The Licensed Site Remediation Professional Licensing Board’s regulations include a provision from the Site Remediation Reform Act, at N.J.A.C. 7:26I-6.3(c), which states:
(c) When there is no specific technical guidance issued by the Department, or in the judgment of the LSRP the guidance issued by the Department is inappropriate or unnecessary to meet the remediation requirements listed in (a) above, the LSRP may use the following additional guidance provided that the LSRP includes in the appropriate report a written rationale concerning why the technical guidance issued by the Department is inappropriate or unnecessary to meet the remediation requirements listed in (a) above, and justifies the use of the guidance or methods that were utilized:
- Any relevant guidance from the U.S. Environmental Protection Agency or other states;
- Any other relevant, applicable, and appropriate methods and practices to ensure the protection of public health and safety and the environment.
It can be argued that PADEP’s VI guidance, with the exception of the NJDEP’s screening levels, from which an LSRP cannot vary, meets the standard of care established by the legislature and codified by the licensing board. Granted there are programmatic differences in the two documents that cannot be easily resolved, but for the technical reasons discussed above, the PADEP’s guidance could be utilized successfully in New Jersey. More importantly, it is hoped that the presentation of these technical differences spurs discussion of how to improve the NJDEP’s guidance in light of the advancement of the science.
– Rodger A. Ferguson, Jr., LSRP
PennJersey President Rodger Ferguson is an active member of the LSRPA Steering, Risk Management and Loss Prevention, and Regulatory Outreach Committees, and currently serves as the Treasurer of the organization and on its Board of Trustees. Mr. Ferguson is a key participant in NJDEP stakeholder groups established for the Technical Requirements for Site Remediation, Remediation Standards, and guidance documents, including the committees established to evaluate alternative and clean fill material protocols (as stakeholder co-chair) as well as the quality assurance and analytical laboratory methodologies required for the investigation of contaminated sites. Mr. Ferguson earned his Bachelor of Science degree in Analytical Chemistry from Ursinus College in 1983 and has 30+ years’ experience in the environmental field. When Mr. Ferguson isn’t at the helm steering PennJersey, he enjoys spending time with his family, rescuing old houses, coaching lacrosse, and suffering with Philadelphia’s professional sports’ teams.
• Licensed Site Remediation Professional 573794
• UST Closure and Subsurface Evaluator 455706