Vapor Intrusion – What is it?

Certain chemicals, when released within the ground can volatilize/ become a vapor and travel through the subsurface while other compounds such as methane gas are generated by buried decaying organic materials. Risk to human health occurs when the potentially harmful vapors or gases enter and accumulate within buildings. Frequently encountered volatile chemicals used for dry cleaning, in manufacturing processes for degreasing metals, and petroleum-based fuels include compounds such as trichloroethylene (TCE), tetrachloroethylene (PCE), benzene, and naphthalene. Buried organic materials can include waste (municipal refuse or industrial byproducts) and/or naturally occurring organic deposits associated with water bodies or wetlands.

Why is Vapor Intrusion a concern?

The accumulation of vapors within indoor air can pose immediate (acute) or long term (chronic) risks to human health through exposure. Methane or petroleum-based vapors could pose an explosion risk.

Learn More – Frequently Asked Questions:

Where do volatile vapors come from?

Volatile chemicals are emitted from contaminated soil and groundwater while methane is generated through degradation of organic material. Potential sources of contamination and the resulting vapors include:

  • Accidental Spills
  • Wastewater Discharge
  • Landfills and Waste Sites
  • Historical or Illegal Dumping
  • Buried Organic Material

The release of these harmful contaminants may have occurred recently or historically (sometimes several decades prior) and may be unknown to current owners and occupants.

What are the applicable regulations?

Contaminated sites are regulated by the United States Environmental Protection Agency (USEPA) and State agencies.

Clean up and risk evaluation criteria include USEPA-established Air Screening Levels (VISLs). State agencies may have additional cleanup standards for sub-slab vapor, soil gas, and indoor air.

How is the risk from volatile vapors and methane addressed?

The most common mitigation strategies include a combination of: removing/treating the source of the volatile vapors or methane, sealing cracks or openings within existing slab or basement floors and walls, and removing volatile vapors or methane from the subsurface via passive or active venting systems before they enter the building or breathing space.

How Can Sigma Help?

Sigma has decades of experience evaluating and addressing vapor intrusion concerns at existing facilities and new developments for residential, commercial, retail, industrial, healthcare, and public/governmental entities. We will assist you by identifying and effectively and efficiently managing your potential risk through our systematic approach that includes:

  • Evaluation and definition of the potential risk through investigation of the site history and current conditions.
  • Development of an appropriate source reduction/remediation and vapor mitigation strategy.
  • Implementation and documentation of remediation and mitigation system installation.
  • Commissioning of mitigation systems to ensure effectiveness.
  • Implementation of long-term monitoring (including continuous remote monitoring, when appropriate) and system maintenance ensuring effective mitigation, risk management, and compliance with regulatory continuing obligations.

We can help you evaluate and address your risk limiting liability, contact us using the form below.

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