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Will Your Next Building Run On Fumes? How To Address Vapor Intrusion Risk And Keep People Safe


One of the major environmental challenges property owners, developers and managers face is vapor intrusion. Vapor intrusion poses a threat to indoor air quality when volatile organic chemicals present in the property’s subsurface soil or groundwater seep into the building.

In extreme cases, these vapors can cause serious hazards including explosions and health effects. If a property is potentially impacted by vapor intrusion, several phases of investigation and remediation may be required, including mobilizations of drilling and laboratory contractors. As a result, multiple sample collection events may potentially increase costs and delay due diligence timelines, according to McAlister GeoScience, a team of geologists and engineers providing practical solutions faced by commercial and industrial real estate professionals. 

During the initial due diligence phase of most commercial real estate transactions, a Phase 1 Environmental Site Assessment, or ESA, is performed to identify potential environmental impacts at the property, including indoor air quality. If a potential risk is identified, such as a leaking underground fuel tank at or near the property, the recommendation is made to perform a Phase 2 ESA.  

Phase 2 ESA consists of collecting samples of soil, groundwater or soil vapor to better define the financial and environmental risks present. In the case of VOCs in the subsurface, the property should be evaluated for vapor intrusion risk utilizing the specific property and building characteristics, said David McAlister, founder of McAlister GeoScience. 

“These evaluations take time and should be performed by an environmental professional with appropriate training and experience to avoid unnecessarily killing your deal or alerting people to an unrealistic risk,” McAlister said. “I always advise my clients to plan ahead for the due diligence process. Do not go for the low-cost leader, and do not rush through the process. Essentially, do not trip over the dollar trying to pick up the pennies.” 

Bisnow spoke with McAlister about the effect of vapor intrusion on properties and some of the solutions to address these challenges.

Bisnow: Why is vapor intrusion a big issue when it comes to commercial real estate transactions?

McAlister: It is the fear of the unknown. If a vapor intrusion condition is actually present, the VOCs seeping into the building may present a cancer threat. This is especially true for what the Environmental Protection Agency calls sensitive receptors, such as children, the elderly, pregnant women and people with compromised immune systems.

Bisnow: What can be done to make the indoor air quality safe?

McAlister: The first thing we need to do when there is a potential risk is run some calculations and evaluate the property based on real data. Unfortunately, it doesn’t do any good to use the conservative values from the EPA’s attenuation factors, which determine vapor intrusion in a building with a crawl space and wooden floor structures. 

Each site is different and requires different engineering controls to mitigate subsurface vapors, such as a site using more modern concrete slab-on-grade construction techniques. It is imperative to hire a qualified environmental professional that can implement different methods depending on the building.

Another useful step is to collect subsurface soil gas and indoor air samples. However, this becomes challenging because fresh paint or carpet in the building can lead to false positives in the samples. If there are VOCs in the breathing zone of the building from subsurface contamination, we can implement building engineering controls, such as a venting system similar to what you would see to mitigate radon gas.

Bisnow: How does McAlister GeoScience approach vapor-contaminated buildings?

McAlister: A carefully implemented scientific investigation performed in a step-wise iterative process is the best approach. Don’t skip steps or cut corners. Due diligence is a very important process. There are plenty of horror stories out there when due diligence was abbreviated and if you are a seasoned commercial real estate professional, you have heard them all.  

We are careful to follow the ASTM guidelines for Phase 1 and Phase 2 ESAs, as well as vapor encroachment guidance. When it comes to mitigation, our geologists and engineers always take the time to look at problems objectively and develop a set of options and solutions making sense for the specific property and its intended use.

Bisnow: What are some of the most common challenges you are seeing?

McAlister: The type of property most often falling into these issues of a vapor intrusion threat is your standard local dry cleaning retailer, usually located in a small shopping center. The unfortunate truth is our most effective dry cleaning chemicals are carcinogenic at very low concentrations. Imagine trying to lease the space next to an active dry cleaner to a daycare center. Believe it or not, this happens and it can be a real challenge.  

Bisnow: What makes McAlister GeoScience stand out from other companies?

McAlister: Here at McAlister GeoScience, we take our time and go through all the steps carefully, keeping public safety in mind. This does not mean the process requires two years in escrow or hundreds of thousands of dollars in consultant fees. We have multiple solutions to help you get your deal done efficiently, preventing it from turning into an endless research project. 

We’ve been successfully helping our clients land their deals with applied engineering, science, chemistry, geology and physics for over a dozen years now. We hope to extend this level of service to many more commercial and industrial real estate professionals for years to come.

This article was produced in collaboration between Studio B and McAlister GeoScience. Bisnow news staff was not involved in the production of this content.

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