SciWorks Radio is a production of 88.5 WFDD and SciWorks, the Science Center and Environmental Park of Forsyth County, located in Winston-Salem.
Recently it has come to the public's attention that two Winston-Salem middle schools are situated within range of a toxic groundwater waste plume. The concern is not the water itself, but the chemical entering the buildings in the form of gas. This is called vapor intrusion.
It is a common problem with tried and true mitigation processes. This week, national leading experts on the topic were invited to The Children's Museum of Winston-Salem and to SciWorks to better inform the community about what's happening.
Basically, there is contaminated groundwater containing PCE, which is a dry-cleaning chemical normally, and some TCE underneath the schools. And typically a building will suck up that contamination into the classrooms. The evidence thus far is that it's not above the state screening levels, but there is cause for concern.
That's Lenny Siegel, Executive Director of the Center of Public Environmental Oversight. This weekend tests will be conducted to find more about the plume.
In major urban areas where there are dry cleaners, there are other industrial activities, it's actually fairly common, and we don't know about it because people haven't looked.If indeed sampling shows that it is unacceptable, or someone says that they're worried that it will be unacceptable in the future, there are things that can be done to protect the occupants of the building.
Mr. Siegel says that the best way to mitigate this problem year-round is to increase the air pressure within the building. That keeps the harmful vapor from rising through the floor. It is a relatively simple solution, with a successful history.
PCE is the principle dry-cleaning chemical perchloroethylene or tetrachloroethylene, It's still widely used in most of the country. TCE is trichloroethylene. It is a solvent that has been used widely in electronics, aerospace, and it's used to clean boilers in schools. So, it's a widespread solvent that's been phased out gradually across the country. Short-term exposure to PCE isn't much of an issue.
According to Siegel, PCE vapor at normal levels carries an extremely low risk. There is a one-in-a-million chance of negative health effects if one is exposed to the chemical vapor for 24 hours a day, over the course of 30 years. The other chemical of concern is less likely to be present, but it does run a much greater risk.
If somehow they find that TCE levels are elevated, that's a concern because TCE is believed to cause, in some cases, cardiac birth defects amongst women who have been exposed in the first trimester of pregnancy.
According to Mr. Siegel, the science shows that exposure to TCE need only be from one day to three weeks to potentially cause this birth defect.
The diseases one is worried most about with exposures to both chemicals are cancers, but they can also cause neurological disease. There are a whole range of things at various doses that might be caused by exposure.
So, how hard will it be to clean this up?
Groundwater contamination is rather complicated. It occurs at various levels and for vapor intrusion you're mostly concerned about loose soil near the surface, but there's also contamination much deeper. Sometimes you clean up the groundwater nearest the surface, and if the stuff is still down below, it may move back up and sort of fill in the gap. I liken it to trying to clean up a dirty lake one scoop at a time. The other stuff is going to move to where you cleaned up. It turns out to be very difficult to clean up groundwater that's contaminated with these substances that can move back and forth depending on what's happening with the water pressure under the ground. Even the best sampling techniques don't always solve the problem because, as one of the top scientists in the field has said, “it's dark down there. You can just sample spots here and there. You don't really have a complete picture because you're almost blind.
This Time Round, the theme music for SciWorks Radio, appears as a generous contribution by the band
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