Around the country, communities are beginning to understand that sites contaminated with toxic industrial chemicals pose another danger to surrounding neighborhoods: vapor intrusion. Families who had contaminated groundwater in their neighborhood–and believed that the problem was taken care of after being connected to clean water–are now being told that the air in their homes might be contaminated by vapor coming from the contaminated groundwater.
It can be a real problem for families living close to Superfund or contaminated sites that were never completely remediated. Many times the original contamination was never cleaned up–especially if it was not considered a serious problem either because neighbors had a different source of water to begin with or had been switched to a safe water supply–and the chemicals were allowed to keep contaminating the groundwater. Those chemicals in the groundwater may now be turning into gases and threatening homes with vapor.
There are several ways that toxic vapor can intrude into the air inside homes and threaten the families who live there. But how does that happen? Here are nine elements that are present in typical vapor intrusion scenarios:
1. Chemicals were dumped, spilled, or buried at or around a factory, dry cleaner, or other business. Sometimes, these chemicals were dumped as many as 50-60 years ago by companies that were careless or lazy or ignorant of the dangers of behaving this way.
2. The chemicals are volatile chemicals (also called volatile organic compounds or VOCs). This means that over time they can volatilize, or turn into a gas. Some examples of these types of chemicals are TCE, DCE, PCE, vinyl chloride, and petroleum-based chemicals.
3. The chemicals were not cleaned up after they were dumped on the ground or were buried on the property. They remained there, sometimes for many years.
4. The soil between the ground surface and the groundwater is porous at the contaminated site. This allowed the chemicals to bleed down through the soil into the aquifer, contaminating the groundwater.
5. The groundwater underneath the contamination is shallow. In most vapor intrusion cases, there is not a great distance between the contaminated groundwater and the basements of buildings or homes above. Usually the distance is between 5 – 40 feet. The shallower the groundwater, the more likely that there will be a vapor problem.
6. The groundwater flows towards homes and businesses. If this is the case, contaminated groundwater can end up directly beneath homes and businesses, turn into a gas and migrate up through the soil and into the homes in a neighborhood. And this can happen even if the family is not (or is no longer) using groundwater to supply water to the home.
7. Homes that are near the contaminated site. Homes that are near the original source of the contamination are most at risk. Most homes that are in danger of vapor intrusion are less than ½ a mile from the contamination source.
8. Older homes are the most vulnerable. These homes sometimes have open crawl spaces, dirt basements, or cracked concrete floors which makes it easier for gas to enter the home. However, even newer homes are at risk. Newer concrete floors can have tiny cracks, and many homes have an opening for a sump pump as well. Volatile chemicals are very persistent and only need a tiny opening to invade a home.
9. Vapors can be present on every level of a home. Do not assume chemicals in vapor form stay in the basement. Gases can travel up through a stairwell or circulate throughout the HVAC system or through spaces behind the walls. For this reason, it is not enough just to test the basement. You need to test every floor for vapor.
Vapor intrusion is being revealed as potentially a major problem all across the country. Superfund sites and other contaminated sites that were not properly cleaned up are still bleeding volatile chemicals into the soil, down to the groundwater and into neighborhoods, potentially in the form of vapors. If you live near one of these sites, demand testing for vapor intrusion in your neighborhood.