Beware of Toxic Vapors Lurking Below
By Katie Zemtseff
Journal Staff Reporter
February 19, 2009
Changes in vapor intrusion rules could spawn a niche market for contractors
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Photos Courtesy of Farallon Consulting A roof-mounted blower, part of a sub-slab depressurization system, discharges contaminated vapors into the air, rather than into a confined space. |
If you work with contaminated properties in any way, a new environmental issue is likely to change the way you do business in the coming years. Called vapor intrusion, the issue could create a niche market for contractors and require more testing of properties.
Vapor intrusion happens when a property is contaminated and a chemical from it leaks into the groundwater. Once volatile organic compounds — such as gasoline, diesel or solvents — get into soil or groundwater, they evaporate and produce vapors that travel up through the soil. If a home or business happens to be located nearby, vapors can enter through crawl spaces or cracks in the foundation, causing unhealthy indoor air quality.
The state Department of Ecology has general language about vapor intrusion in its Model Toxics Control Act, adopted in 2001. Currently, Ecology requires vapor intrusion to be examined on a case-by-case basis with Ecology cleanup project managers deciding whether to investigate or not.
But a lot has changed since 2001. The science behind vapor intrusion has progressed, problems associated with it are better understood and the Environmental Protection Agency has released more information on the topic. To keep up with the changes, Ecology is starting a rulemaking process this month to clarify how to deal with the problem.
Changing Business
Pete Kmet, an environmental engineer with Ecology's Toxics Cleanup Program, said Ecology wants to add more specific requirements in testing for vapors and making sure cleanups address the potential for vapors to get into buildings.
“Yes, I think this will result in paying more attention to this potential exposure pathway,” he said. “It will put an added emphasis on checking to make sure vapors are not present at significant levels.”
Kmet said Ecology plans to issue guidelines this summer that clarify how to deal with vapor intrusion.
Martha Hankins, supervisor of the Policy and Technical Support Unit at Ecology's Toxics Cleanup Program, said the current law is confusing. The guidelines, she said, will clarify Ecology's current regulations and what Ecology expects of people investigating the issue. It will not carry legal weight until the information is codified in Ecology rules. But the changes are expected to be significant.
“It's a priority to address and clarify what is required under vapor intrusion,” she said. “It's not so much that our thinking has changed, it's just that we know more and can be more specific.”
Kmet said one reason for providing guidelines is to make sure consultants dealing with contaminated properties know vapor intrusion can be “a pretty significant issue at many sites.” Consultant knowledge varies greatly, he said.
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Photos Courtesy of Farallon Consulting Farallon employee Daniel Caputo collects sub-slab soil vapor samples. |
Rich McManus, principal engineer at Farallon Consulting, is concerned about vapor intrusion and how it could affect clients. McManus said everybody involved with the acquisition or sale of properties that have been contaminated should understand the importance of vapor intrusion and how it could affect them. Many, he said, do not.
“There may be this skeleton in the closet that none of us have been aware of until now,” he said. “Projects where (people) thought there were no problems, there could be problems that can come back to haunt you.”
McManus said there is also a “huge disparity” between the way individual projects are being managed, and he is looking forward to clarification in the guidelines.
McManus said New York has done a lot of work on vapor intrusion. New York issued a guidance document in 2006 on the issue and it has begun reassessing projects that previously were approved after cleanup to check for vapor intrusion.
In Washington, Kmet said vapor intrusion is unlikely to be an issue at most projects that have undergone cleanup. However, it could be an issue at sites where chemicals still in the ground have been capped. Ecology reviews these projects every five years, and would consider vapor intrusion to a greater degree after rules go into effect.
“It's really only those sites that still have significant amounts of solvent or other volatile chemicals left,” Kmet said, “that never really adequately cleaned up in the first place. Those are the sites that we're going to have to go back and take a second look at.”
Hankins said there are about 300 of those sites in the state, only some of which might have vapor intrusion issues.
Fixing the Problem
One way to fix vapor intrusion is to install a sub-slab depressurization system. This is often done by companies who have worked on similar systems for areas with radon problems on the East Coast. McManus said those companies are likely to see more business as the country begins to regulate vapor intrusion to a larger extent.
“They will be expanding ... into a more broad niche in more diverse locations in the country,” he said.
According to the Interstate Technology & Regulatory Council, sub-slab depressurization systems generally cost between $1 and $2 per square foot for residential structures and between $1 and $5 per square foot for commercial and other structures.
McManus used a sub-slab depressurization system, in- stalled by Advanced Radon Technologies of Spokane, to fix a vapor intrusion problem at an undisclosed gas station with a leaky underground storage tank. Prior to the fix, workers in a nearby strip mall complained that it smelled like gas inside, though it didn't smell outside.
It turned out that when it was windy, the wind would depressurize the building because of how the structure was designed, drawing vapors from the ground into the strip mall. Pipes, cracks in the concrete and construction joints were all letting unhealthy fumes into the building. In one cabinet, McManus said, “the smell of gas would have knocked you over.”
The sub-slab system used negative pressure to suck the vapors out of the soil below the building's foundation, before releasing them above the building's roof. The chemical levels were not strong enough to be problematic in outdoor air, but were in an enclosed space.
Scientists keep redefining the levels for which contaminants cause a problem in the human body. Because of this, McManus said once a project team is asked to investigate vapor intrusion, it will likely find a problem. “It doesn't take a lot to be considered an issue,” he said.
Farallon clients are beginning to run into situations where Ecology asks about vapor intrusion, he added.
McManus said the topic has changed the way his firm approaches projects. “You don't think of those dynamics when you normally think of cleanups,” he said. “(We) hadn't thought of environmental cleanups as having those issues and we're discovering they are actually significant issues and they do need to be addressed.”
McManus wants the entire industry to be aware of the problem.