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This presentation is an excerpt from the 2-day vapor intrusion training course that Dr. Hartman has been presenting to Federal & State regulatory agencies, DOD facilities, agencies in Australia, Israel & Brazil, and numerous stakeholders around the country. The training has been given to 16 locations around the United States by the end of 2017.

Lecture notes are at the bottom of each slide so that if played out as a hard-copy, the presentation can be a useful reference document.

This part of the webinar gives an overview of what the VI pathway is and why regulators, consultants, project managers, property owners, companies, banks, lawyers, and insurance companies need to be concerned about it.

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Vapor intrusion refers to the upward migration of contaminants in the vapor phase from groundwater, soil, or soil gas contamination sources.

Key criteria to the risk determination are the risk level, the toxicity of the contaminant, and the exposure factors. These parameters are often much more important than model parameters such as soil porosity and pressure gradients.

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In some cases, there is a real threat to occupants.

But in the majority of cases, the risk to occupants is exaggerated, hence the perception is greater than the real risk. Nevertheless, you need to worry about it because the EPA has identified it as a risk pathway, numerous states have their own guidance or policies, and citizen groups and of course, attorneys are making it an issue.

Vapor intrusion sensationalism!

Vapor intrusion cases making headlines around the country – even the National Enquirer!

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The EPA & many State guidances use the distance criteria listed above to screen sites needing to assess the pathway.

At sites with existing contamination but no current buildings, the pathway will need to be assessed when development is proposed.

Attorneys and community activist groups can expand these criteria beyond the EPA limits.

In some recent cases, concern about the safety of burrowing animals, and fruits & vegetables has been the reason to assess the vapor intrusion pathway.

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The list of compounds that are in the EPA VI guidance and some State guidances include VOCs and semi-VOCs.

The TPH aliphatics are particularly problematic because their proportion in petroleum vapor is high and their toxicity is unknown.

The semi-VOCs are particularly problematic because the risk-based screening levels (RBSL) are typically very low (e.g., for PCBs, the RBSL is 10 to 100 times lower than benzene).

Common sites that may be susceptible for vapor intrusion problems are any locations containing VOCs. Most commonly, USTs, tanks, piping, and re-fueling operations associated with petroleum hydrocarbons. In the colder climates, homes with internal oil tanks are potential candidates.

Common sources for chlorinated compounds are dry cleaners (PCE), engine & parts cleaning areas with vapor degreasers (TCE, TCA) and any circuit board manufacturing facility.

Semi-volatile sites include MGP sites and any sites with electrical power facilities.

Contamination may exist in the soil, groundwater, or as vapor clouds. Structures overlying or near these sources may be at risk.

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For the vapor intrusion risk pathway, acceptable concentration levels are 100 to 10,000 times lower than acceptable levels for soil and water. So essentially, this increases the number of sites that have to be evaluated.

This table gives a summary of the TCE and benzene groundwater values which exceed the 1 in 1 million cancer risk using the EPA version of the J-E spreadsheet. The default vapor intrusion criteria currently used by EPA and many other agencies are so conservative that few sites are screened out in the screening evaluation step. Some of the values are below laboratory detection levels meaning that even the non-detects fail. Further assessment requires more data which means more expense.

What does it all mean?

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The result is that the vapor intrusion pathway has legs, meaning it will be a concern for quite some time.

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In this part of the webinar, we will review some of the vapor intrusion guidance documents in the United states. If you are a consultant or responsible party, you need to know which agency has jurisdiction and what their vapor intrusion policy is in order to know what approaches are allowed and what the allowable levels are.

The hottest VI Regulatory topics as of December 2017. Some of the previous-hot topics have cooled down, but there still exists a couple of very hot ones.

A summary of the good points, bad points and ugly points in the 2015 EPA OSWER guidance.

The conflicting information & poor writing style will lead to more confusion for environmental professionals which will lead to an increase in the number of sites that need a vapor intrusion assessment.

A summary of the good points, bad points and ugly points in the 2015 EPA OUST guidance.

Despite some flaws, this guidance will lead to a reduction in the number of sites that need a vapor intrusion assessment.

EPA-OUST guidance adopted exclusion criteria for UST sites. Note requirement for clean soil

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These are the States that have adopted exclusion criteria for petroleum VI sites as of November 2015. If the criteria are meant, the vapor intrusion pathway is considered to not be an issue and can be thrown into the VI out basket. It is likely more States will be doing the same. The recently released ITRC guidance also contains exclusion criteria.

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Based upon the 2015 EPA OSWER guidance, allowable levels for benzene in groundwater will be ~3300 times lower than the exclusion criteria by EPA-OUST (Office of Underground Storage Tanks).

Regardless, OSWER is claiming jurisdiction for all petroleum sites except for UST sites. So the lower screening values will apply at all of these sites.

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Soil gas allowed values for benzene. The OSWER values are far below California’s and 100,000 times below EPA-OUST value. This is because the OSWER values do not incorporate bioattenuation.

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As of January 2015, 36 states have VI guidance.

Some recent updates/revisions made by some States since summer 2017.

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ITRC released a vapor intrusion guidance document in 2007. It consisted of 2 documents: A practical guideline and a separate scenarios document.

ITRC released new guidance specifically for petroleum hydrocarbon sites in October 2014. Web-based and classroom training are currently available. Go to: www.itrcweb.org.

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Appendix G of the ITRG PVI Guidance is a toolbox that describes investigation methods and analysis methods.

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ASTM convened a technical workgroup in 2005 to write a standard for vapor intrusion as it applies to property transactions. The standard was originally released on March 3, 2008. A revised standard was released in June 2010.

In November 2013, the Phase 1 standard was updated to include vaporintrusion as a REC.

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The Standard identifies the following search distances. Note the long distances.

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Liability concerns is a big part of vapor intrusion. Those at risk include consultants, property owners (past, current & future), lenders, and insurance companies.

One of the currently hot topics is the Federal and State agencies shift away from the use of models to demonstrate the VI pathway is not a risk. More and more states are jumping on the band-wagon. EPA has removed the Excel version of the J-E models from its website and has replaced it with the vapor intrusion screening level (VISL) calculator.

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EPA surprisingly released a new version of the J‐E model as an Excel workbook in September 2017 .  However the text on the ReadMe page in the workbook says this model does not replace the VISLs.  Then what’s the point of the spreadsheet?

A quick run using the new model gives screening values for a residence about 5 times higher than the VISL and 

The current hottest topic throughout the VI world: Short term TCE exposure

The Johnson study upon which current short-term standards are based was actually an oral exposure not inhalation and the results of the study can not be replicated although many studies have tried to do so. So why have the results been adopted?

A recent study in 2017 being conducted by an industry group could not repeat the dosages in the Johnson study. What does this tell you?

Recent text from a November 2016 document released by EPA R7 which says that the period of exposure for short-term TCE effects is not over a 21 day period but at any time during the 21-day period. The standards they set for residential vs commercial assume an exposure of roughly 48 ug of TCE.

So does this mean exposures as short as 6 minutes could cause harmful effects?

In April 2016, Massachusetts announced it was re-opening 1000 TCE sites using lower allowed levels.

In May 2017, Michigan announced it was reevaluating 4000 TCE sites with lower allowed levels.

This is a partial list of States that are re-opening TCE sites to re-assess the VI pathway.

There are 2 options for assessing the short-term TCE exposure.

One is to collect samples over a period of time, such as the 21 day exposure period. However passive collectors have serious limitations, incorrect exposure period for non-residential receptors, no resolution (only 1 data point) and no real-time feedback. If the exposure period of concern is 24 hours or a few days, passive collectors also become prohibitively expensive.

The second option is to use continuous analyzers.

Picture of the Vaporsafe continuous monitoring system.

14 days of PCE concentrations inside an active Print Shop: every night values increased, but were low during the day. It was determined to be due to the HVAC system.

But the continuous monitoring showed that values were below allowable levels during the period when people were working.

The dot in red shows the results if you had deployed a passive collector for 14-days. If a 14-day passive sample was collected, the one value would have been biased high & indicated a problem. A false positive.

TCE in Master Bed vs. time. Air Infiltration Units turned off after a few days, then SSD turned off a few days later. Note that the mean TCE concentration during air filtration was 1.9 ug/m3, then jumped to 4.2 ug/m3 while SSD was operating. Once SSD was turned off, the mean concentration dropped to 2.6ug/m3. We observed daily fluctuations, but the key point is that the SSD system operation resulted in higher mean and peak concentrations, and this was detectable using high resolution chemical analyses.

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Six days of continuous monitoring of TCE at another large commercial warehouse in San Diego. The huge increases occur at about the same time every day. What is causing this to happen?

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Comparison of the indoor TCE values to barometric pressure shows an increase in TCE concentrations when there is a drop in barometric pressure.

Comparison of the indoor TCE values to sub-foundation pressure shows a direct correlation between indoor air concentrations to positive pressure under the slab.

TCE indoor air concentrations in a furniture manufacturing facility. Concentrations were low at night, but then increased during the work day. If vapor intrusion was the source, values should have increased at night when the facility was closed up. The opposite was observed. What was the TCE source?

Ohio EPA’s rapid response actions for TCE in Groundwater (August 2016)

Ohio EPA’s rapid response actions for TCE in Sub-Slab Soil Gas (August 2016)

These are some of the options if urgent response is needed. Continuous monitoring can help decide which of the remedies is mitigating the problem.

TCE concentrations in 4 locations in an operating facility. Note instant drop when the mitigation system was started-up

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TCE concentrations in a basement at an industrial facility.  Values for approximately a month ranged from 4 ug/m3 to 14 ug/m3.  But when the two floor sumps were sealed up, values crashed to zero within a couple of hours. 

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