Vapor Intrusion (VI)

What is it and why should I care?

February 23, 2017

Farmington Hills, MI | Windsor, ON | Toronto, ON

Matthew Schroeder, PE and Jeffrey Bolin, CHMM

What is Vapor Intrusion?

Vapor Intrusion (VI)Conceptual Site

Model

Why Should We Care?

Text

10 years ago VI was not typically evaluated in RIs

Now VI concerns are often a driver for investigations and

remediations Included in ASTM Phase I standard

Recently added to Superfund scoring*

Why Should We Care?

Why Should We Care?

My site is closed!• We all heard MDEQ say “A deal is a deal”

but…

Why Should We Care?

VI is regulated differently depending on location, and the guidance is changing rapidly

• USEPA guidance (2015)

• State guidance (Michigan, Ohio, Indiana, and Illinois all revised/issued guidance within the last year)

• California, Massachusetts incorporating new science quickly (maybe before proven?)

Why Should We Care?

VI is regulated differently depending on location, and the guidance is changing rapidly

• Inconsistency across jurisdictions on what data is needed and what criteria apply

• Very conservative assumptions used to calculate screening levels

• Difficult to off-ramp once you exceed a screening level

Soil and groundwater?Sub-slab vapor?Indoor air?Models?Attenuation factors?OSHA criteria?

Criteria

Michigan’s Draft Rules (VI)

• Issued in June 2016, revised in October 2016

• Tiered approach to VI assessments• Tier 1 – Initial Screening Levels• Tier 2 – Generic Criteria (incorporate soil type, depth to groundwater)• Tier 3A – Generic Criteria (Use Facility-Specific Land Use & Building Specifications)• Tier 3B – Site Specific Data

• Vapor Intrusion Calculator Tool (under development)

• Generally tries to avoid Indoor Air Testing

Michigan’s Draft Rules (VI)

Note “Facility” Designation

Conceptual Site Model

The Perfect Storm

TCE and Vapor Intrusion

• TCE short-term exposure limits

• Reliability of science doesn’t seem to matter

• Response actions required within days

• Michigan using Department of Health and Human Services to circumvent process and force evacuations until response actions conducted

Image from NBC

How do I determine if VI is an issue at my site?

• Soil and groundwater data

• Subsurface soil gas

• Sub-slab soil gas

• Indoor air

What’s on the horizon (or closer)?

• Overcoming sampling variability• Passive, long duration indoor air sampling• Large volume sub-slab sampling

• Isotope analyses to differentiate sources

• Handheld GC to identify sources to indoor air

Takeaways

• Vapor intrusion assessment is changing rapidly, in the science, regulations, and public awareness

• More so than ever before, vapor intrusion is the driver for remediation/mitigation actions

• Vapor intrusion concerns can kill deals, cause evacuations, and lead to litigation liability

Questions?