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Vapor intrusion announcements
Vapor intrusion is the process of vapors migrating from volatile chemicals in contaminated soil or ground water through subsurface soils and/or preferential pathways (such as underground utilities) and impacting the indoor air quality of any overlying buildings. The volatilization to indoor air pathway (VIAP) is the exposure pathway that evaluates the risk posed from vapor intrusion and direct volatilization.
Following are announcements related to vapor intrusion, including guidance document updates and other valuable information.
Past email communications
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November 20, 2023: EGLE RRD rescinds 2021 Addendum to 2013 Vapor Intrusion Guidance Document
Remediation and Redevelopment Division rescinds the 2021 Addendum to the 2013 guidance document for the vapor intrusion pathway for the acute vapor hazards associated with petroleum releases at Part 213 sites
The Michigan Department of Environment, Great Lakes, and Energy (EGLE), Remediation and Redevelopment Division hereby rescinds the 2021 Addendum to the 2013 Vapor Intrusion Guidance Document (Acute Addendum) for acute vapor hazards (toxicants) associated with petroleum releases at Part 213 sites. The Acute Addendum was created to clarify expectations for complying with Section 21307 and to address vapor hazards from acute toxicants for leaking underground storage tank releases.
Note that the Acute Addendum addressed only Part 213 releases, which are mostly only petroleum compounds, and the vapor intrusion to the indoor air pathway. While most Part 213 releases are petroleum, it is possible for a Part 213 release to include chlorinated compounds and other hazardous substances. In instances where chlorinated compounds or other hazardous compounds are released at a Part 213 site, additional consideration of the vapor intrusion to indoor air pathway is necessary.
To ensure EGLE’s guidance is protective of public health and representative of real-world scenarios, EGLE has evaluated data collected at over 90 petroleum contaminated sites. Of the 19 chemicals addressed in the Addendum, ethanol, diisopropyl ether, n-propylbenzene, and toluene are either additives of petroleum or the base components of petroleum and are the acute toxicants associated with Part 213 petroleum releases. EGLE’s data evaluation determined soil gas screening levels were not exceeded for any of these compounds except toluene. Toluene did not exceed soil gas screening levels at most sites; however, at a small number of sites where soil gas samples were collected very near or within a petroleum non-aqueous phase liquids (NAPL) body, toluene concentrations exceeded screening levels. Petroleum vapors, including toluene, rapidly degrade under aerobic conditions, therefore, the likelihood of an acute exposure from a petroleum hydrocarbon is extremely low. Based on the data evaluation, EGLE determined the sampling plan outlined in the addendum is unnecessary and the potential risks from acute petroleum hydrocarbons can be evaluated the same as other hydrocarbons at Part 213 sites.
Section 21307(2)(a) requires that acute vapor hazards from a petroleum release be evaluated. For acute hazards from potentially acute toxicants, if a potential source of vapors is present (NAPL is present or soil and/or groundwater screening levels are exceeded), there are generally 2 options for the evaluation: 1) Use vertical or horizontal separation distances to screen out a structure; 2) Use a hierarchy of soil gas and air data – if soil gas exceeds screening levels, collect sub-slab samples; if sub-slab samples exceed screening levels, collect indoor air samples. Site specific or alternative options may also be proposed for evaluation. This evaluation of the acute vapor hazards is only applicable to new releases and releases conducting initial response actions. If, at any point in the evaluation, petroleum odors have been identified in a structure, NAPL has been found to be entering directly into the structure, and/or fire and explosion hazards potentially exist, then mitigation and/or increased monitoring frequency will be necessary as part of the initial response actions under Section 21307.
Guidance on petroleum vapor intrusion and sampling for the risk evaluation from non-aerobically degrading acute toxicants will be released in the near future. In the interim, these will be evaluated on a site-by-site basis.
- Questions regarding this rescission may be directed to Nick Swiger, Technical Support Unit Manager, at SwigerN@Michigan.gov or 231-429-8926 or Matt Williams, Volatilization to Indoor Air Specialist, at WilliamsM13@Michigan.gov or 517-881-8641.
- Questions regarding the toxicology may be directed to Dr. Shane Morrison at MorrisonS5@Michigan.gov or 517-230-7570.
- Questions regarding the application of the guidance to a specific site should be directed to district staff where the site is located.
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October 11, 2023: EGLE RRD issues guidance for the evaluation of a dispersed source in urban fill for the VIAP
EGLE RRD issues guidance for the evaluation of a dispersed source in urban fill for the VIAP
The Department of Environment, Great Lakes, and Energy (EGLE), Remediation and Redevelopment Division (RRD) has issued guidance on the evaluation of a dispersed source in urban fill for the volatilization to indoor air pathway (VIAP). RRD has recognized the challenge urban fill has presented property owners and developers when evaluating the VIAP. The guidance outlines and clarifies RRD’s expectations with site characterization for all contaminants associated with urban fill and for when this evaluation process is applicable. In addition, several options for the evaluation of the VIAP are provided to give property owners and developers maximum flexibility. Training on the use and applications of the document will be provided in the next few months.
With the public release of this guidance, RRD will be rescinding the Vapor Paper entitled “Evaluating Mercury in the Soil for the Volatilization to Indoor Air Pathway (VIAP)” that was released on December 3, 2019 to guide EGLE staff.
Questions regarding this document may be directed to Matt Williams, Volatilization to Indoor Air Specialist, at WilliamsM13@Michigan.gov or 517-881-8641 or Nick Swiger, Technical Support Unit Manager, at SwigerN@Michigan.gov or 231-429-8926. Questions regarding the application of the guidance to a specific site should be directed to district staff where the site is located.
Resources: Evaluation of a Dispersed Vapor Source in Urban Fill Under Part 201
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October 3, 2023: Updated Cover Sheets: Site-specific target levels and Part 213 Submittals
Site-specific target levels and Part 213 Submittals
The Michigan Department of Environment, Great Lakes, and Energy (EGLE), Remediation and Redevelopment Division (RRD) has updated the cover sheets for Part 213 submittals to reflect a change in the site-specific target level (SSTL) review process under Part 213. The previous reference to Section 20120b of Part 201 that specified a 90-day timeframe for the department to review site-specific criteria has been removed because it does not apply to SSTLs developed as part of corrective actions implemented under Part 213. Under Part 213, SSTLs are neither approved nor denied. Rather, corrective actions are determined to be protective of public health, safety, welfare, and the environment through the selective audit of Final Assessment Reports and Closure Reports.
The cover sheets for submittals under Part 213, including Initial Assessment Report (EQP4002), Final Assessment Report (EQP4000), Supplemental Information Report (EQP4001), and Closure Report (EQP4008) are updated with SSTL-related information, appearing in item #2 of the cover sheets.
The appropriate “yes” checkboxes must be marked to indicate that SSTLs (for any pathway) have been developed by the owner/operator (O/O) or that the 2020 volatilization to indoor air pathway (VIAP) screening levels are used as VIAP SSTLs with associated documentation. If the report does not rely on SSTLs developed by the O/O or the use of the 2020 VIAP screening levels, then the appropriate “no” checkboxes in item #2 of the cover sheet should be marked. There are no checkboxes on the cover sheets related to generic risk-based screening levels or RRD-developed SSTLs.
RRD will provide feedback on SSTLs as appropriate through the selective audit of Final Assessment Reports and Closure Reports. It is also RRD’s intent to provide feedback on SSTLs presented in reports that were not selected for audit or in non-auditable reports to ensure that corrective actions are protective of public health, safety, welfare, and the environment.
- For questions related to the Part 213 program, please contact Dr. Steve Beukema, Part 213 Program Specialist, at BeukemaS@Michigan.gov or 269-547-0125.
- For questions related to VIAP SSTL development, please contact Dr. Shane Morrison, RRD Toxicology Specialist, at MorrisonS5@Michigan.gov or 517-230-7570.
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August 7, 2023: Remediation and Redevelopment Division reissues Non-Aqueous Phase Liquid Characterization, Remediation, and Management for Petroleum Releases Guidance
Remediation and Redevelopment Division reissues Non-Aqueous Phase Liquid Characterization, Remediation, and Management for Petroleum Releases Guidance
The Department of Environment, Great Lakes, and Energy, Remediation and Redevelopment Division (RRD) has updated and reorganized its guidance for the characterization, remediation, and management of petroleum non-aqueous phase liquids (NAPL). It provides current references (e.g., department name, statute, and rules), clarifies RRD’s expectations with NAPL characterization using a multiple lines of evidence approach, clarifies when generic criteria or risk-based screening levels can be utilized, and outlines how to move a site with petroleum NAPL to closure or no further action. In addition, an example multiple lines of evidence evaluation table is provided as an appendix to give all users a tool and an example of how to organize site data for the evaluation of petroleum NAPL in the development of the conceptual site model. Training on the use and applications of the document will be provided in the next few months.
- Questions regarding this document may be directed to Nick Swiger, Technical Support Unit Supervisor, at SwigerN@Michigan.gov or 231-429-8926.
- Questions regarding the application of the guidance to a specific site should be directed to staff in the district office where the site is located.
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April 6, 2023: EGLE RRD specifies soil gas sampling requirements for Final Assessment Reports
EGLE RRD specifies soil gas sampling requirements for Final Assessment Reports
The Department of Environment, Great Lakes, and Energy (EGLE), Remediation and Redevelopment Division (RRD), is publishing the following policy to clarify the number of soil gas sampling events required for a Final Assessment Report (FAR). This policy was developed based on RRD's current knowledge of biodegradation of petroleum vapors and developed to be protective of human health and the environment while allowing corrective actions to move forward at petroleum releases regulated under Part 213, Leaking Underground Storage Tanks, of the Natural Resources and Environmental Protection Act, 1994 PA 451, as amended. The policy will reduce the number of unnecessary FAR extension requests related to obtaining multiple rounds of soil gas samples prior to FAR submission. It will also allow FARs to be submitted with ongoing soil gas sampling proposed in corrective action plans, as appropriate.
If an owner or operator is using soil gas samples to evaluate the volatilization to indoor air pathway (VIAP) as part of a risk-based corrective action site assessment, RRD has decided that it is often not practicable to conduct multiple soil gas sampling events prior to the due date for a FAR, as required by Section 324.21311a. Thus, multiple rounds of soil gas sampling is not required for the purposes of a FAR. This is consistent with the approach for delineating the extent of groundwater contamination, which is often based on a single groundwater sampling event in the FAR and followed up with multiple sampling events prior to closure to demonstrate groundwater plume stability. As appropriate, a corrective action plan to address the VIAP would include additional soil gas sampling with a contingency plan to address unacceptable risks.
RRD is developing guidance for evaluating the VIAP for petroleum releases regulated by Part 213. Until such guidance is finalized, the following recommendations from Table 4‑1 and 5-3 in the 2013 Guidance Document for the Vapor Intrusion Pathway are offered to evaluate the VIAP prior to closure. Generally, when evaluating VIAP risks from petroleum, use row 1 when evaluating the VIAP risk from soil/groundwater, use row 2 when evaluating from non-aqueous phase liquid (NAPL) that is stable (residual or mobile NAPL), and use row 3 when evaluating from NAPL that is not stable (migrating NAPL).
- For questions regarding the Soil Gas Sampling Requirements for Final Assessment Reports, please contact Steve Beukema, Part 213 Program Specialist, EGLE, RRD, at 269-547-0125, or BeukemaS@Michigan.gov.
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March 14, 2023: EGLE RRD recommends reassessment of petroleum vapor intrusion pathway
Remediation and Redevelopment Division recommends reassessment of petroleum vapor intrusion pathway after update to the precluding factors checklists
On January 10, 2023, the Michigan Department of Environment, Great Lakes, and Energy (EGLE), Remediation and Redevelopment Division (RRD) revised the Precluding Factors Assessment Checklists for PVI Separation Distances. The revised Precluding Factors Assessment for the PVI Lateral Inclusion Zone Checklist and the Precluding Factors Assessment for the PVI Vertical Separation Distances Checklist update and clarify the use of both the lateral and vertical distances to appropriately screen out structures and properties from further evaluation of the volatilization to indoor pathway (VIAP) for petroleum releases.
If an Owner or Operator (O/O) previously submitted a Final Assessment Report (FAR) or Closure Report (CR) under Part 213, Leaking Underground Storage Tanks, of the NREPA, and received an insufficient information determination or denial due solely to evaluation of the VIAP, RRD recommends the O/O reevaluate the submittal.
After reevaluation, RRD recommends the O/O revise their FAR or CR to include this updated evaluation and resubmit a revised FAR or CR to the RRD District Office for audit under Part 213 if the following information is true for their submittal:
- the O/O determines that the PVI separation distances would now apply,
- the O/O can demonstrate the VIAP has been adequately evaluated, and
- the O/O can demonstrate any exposure risks will be appropriately addressed as part of the corrective action in the FAR or any exposure risks have been appropriately addressed as part of a corrective action completed for the CR.
Additional information can be found by viewing the webinar Petroleum Vapor Intrusion - Updates to the Lateral Inclusion Zone Checklist and Vertical Separation Checklist.
- For questions regarding the Precluding Factors Assessment Checklists for PVI Separation Distances and the VIAP in general, please contact Matt Williams, EGLE, RRD, at 517-881-8641, or Williams13@Michigan.gov.
Technical contacts
Dr. Shane Morrison, Toxicology Volatilization to Indoor Air Specialist, MorrisonS5@Michigan.gov or 517-230-7570.
Matt Williams, Volatilization to Indoor Air Specialist, WilliamsM13@Michigan.gov or 517-881-8641.