Vapor Intrusion Assessments & Hidden Risks

Vapor Intrusion: A hidden risk for new developments

VAPOR INTRUSION: A hidden risk for new developments

Development stakeholders have an array of risks to consider when constructing each new property or redevelopment of existing properties: placement of utility lines, safety compliance, the storage of hazardous materials, dry cleaning operations, industrial facilities, and manufacturing for example. But there is another invisible risk beneath a property’s surface that could degrade the quality of your building, property and indoor environment, before it’s even finished: vapor intrusion, a problem that often goes unnoticed to building occupants.

A site assessment is necessary to determine just how invasive these intrusive vapors will be in your building.

Consider Vapor Intrusion Assessment for Your Property

Vapor intrusion occurs when there is a migration of volatile organic compounds (VOCs) or chemicals from a subsurface source (i.e., contaminated groundwater or soil) into an overlying building’s indoor air. Vapors in soil gas enter buildings through:

cracks in the foundation
openings for utility lines, plumbing and other conduits, such as electrical outlets

Examples of volatile and semi-volatile chemicals include de-greasers, dry-cleaning solvents, gasoline and petroleum (including benzene), naphthalene, polychlorinated biphenyls (PCBs), and certain pesticides. In late 2016, the EPA began risk evaluation of many chemicals associated with vapor intrusion.

In extreme cases, the vapors may accumulate into dwellings or occupied commercial and industrial buildings to airborne concentrations that may pose:

Near-term safety hazards (e.g., explosion)
Acute and adverse health effects

In buildings with lower concentrations of vapor-forming chemicals arising from vapor intrusion, the main concern is whether the chemicals may pose an unacceptable risk of health effects due to long-term (i.e., chronic) exposure.

So how do you know vapor intrusion should be investigated on your property/development? In the EPA’s terms, vapor intrusion is a potential concern at any building–existing or planned-building located near soil or groundwater that is contaminated with VOCs. This includes contaminated sites located within the near vicinity of your property. In general, sites most commonly contaminated with VOCs in the commercial and industrial areas may include the current or former businesses of following nature:

Manufacturing plants
Chemical processing plants
Landfills
Warehouses
Train yards
Dry cleaners
Gas stations
Coal gasification plants
Printers
Automobile repair shops
Any site where USTs (underground storage tanks) are leaking

Courtesy of MASSDep – This illustration portrays the potential for vapor intrusion on differing types of properties.

Developers and Property owners should also keep in mind that vacant properties may contain VOC contamination. As you can see in the illustration above, wind effects, groundwater flow, and stack effects (pressure differences inside and outside a building caused by differences in indoor and outdoor temperatures) are all factors when assessing vapor intrusion.

The EPA recommends that if vapor intrusion is a concern on your property, a risk assessment by qualified personnel is necessary to evaluate the degree of risk to future building occupants. If you are not sure based solely on the property’s location or current state whether a risk assessment should be conducted then it I necessary to research the history of the property, surrounding properties, site geology and hydrogeology, among other site characteristics, before beginning sampling and analysis.

Sampling and Analysis of Vapor Intrusion

Until fairly recently, there wasn’t much reason to believe vapor intrusion was anything more than an indoor air issue that could be assessed through indoor air sampling. In past years, many environmental consultants and services providers did not account for potential vapor intrusion impacts in Phase 1 site assessments. Omega principals know from decades of experience that vapor intrusion is a holistic environmental issue requiring multiple lines of evidence to form the most accurate site characterization and the best solution for mitigation. The initial step in creating a vapor intrusion mitigation plan is forming a conceptual site model, but first, sampling and analysis will be necessary through a combination of the following methods:

Characterize the nature and extent of subsurface vapor sources using:

1. Indoor Air Sampling
2. Sub-Slab Soil Gas Sampling
3. Soil Gas Sampling
Compare sample concentrations to health-based screening levels
Conduct and interpret human health risk assessment:

Perform indoor air risk analysis (modeling indoor-air risks using modified Johnson and Ettinger model for soil-gas and groundwater) to evaluate the potential for vapor intrusion.

Evaluate the vapor intrusion modeling results to determine whether the concentrations of VOCs detected in the soil vapor samples at the site present any potential unacceptable health risks to the workers/tenants inside the building.

If you think your property may be at risk for vapor intrusion or other subsurface contamination, Omega can help you characterize the issue and form a cost-effective mitigation plan. Please call us at (949) 252-2145 for more information.

Omega Environmental Services, Inc. has qualified and certified professionals (Certified Industrial Hygienists, Professional Engineers, Hydrologists, Geologists, Certified Asbestos Consultants, Certified Lead Professionals, Toxicologists) that have the expertise to assist businesses in assessing and managing hazardous materials and facilitating construction.

Sources and Further Reading on Vapor Intrusion