Before 2003, the New York State Department of Environmental Conservation (DEC) cleaned up contaminated sites under certain set guidelines and to meet certain standards that they had at the time.

In late 2002, early 2003, research regarding vapor intrusion, which is the process by which volatile chemicals move from a subsurface source into the indoor air of overlying or adjacent buildings, began to yield more information.

After learning about the new threats of vapor intrusion, DEC staff went through records of sites that the DEC was involved with, either in an oversight or a managing capacity. The sites that were cleaned up prior to 2003 and where remedial decisions had already been made, which include over 400 in New York State and approximately 80 on Long Island, are now going to be prioritized and then addressed and evaluated for potential vapor intrusion. The process of prioritizing the sites is expected to be completed by December, according to the DEC.

Of the 400+ sites, two are located within Levittown, including American Drive-In Cleaners and Arba Cleaners.

"All of the sites are going to be prioritized and we will be doing investigations based on sites that have the highest risk potential and those will be addressed and investigated first," said Maureen Wren, public information officer for the DEC. "Every site will be evaluated on a case-by-case basis and if there is a need for DEC or Department of Health staff to conduct indoor air quality tests, the homeowner, business owner or other property owner would be involved."

According to the DEC, they will ask the party responsible for contaminating the site to pay for and perform the vapor intrusion evaluation, as well as any site investigations and the installation and long-term operation and monitoring of any mitigation system which would be required. If the responsible party refuses to perform these activities, or if no viable entity remains, the state will take responsibility for them, and will pursue cost recovery as in any Superfund site. This is the same with groundwater contamination.

According to the DEC's website, vapors can enter buildings in two different ways. In rare cases, vapor intrusion is the result of groundwater contamination, which enters basements and releases volatile chemicals into the indoor air. In most cases, vapor intrusion is caused by contaminated vapors migrating through the soil directly into basements or foundation slabs. Although the DEC historically has evaluated soil-gas pathways, improvements in analytical techniques and the knowledge gained from remedial sites in New York and other states has increased their understanding of how vapor intrusion occurs.

"Historically, we thought that vapor intrusion was only an issue where the source of the contaminants was very shallow and the magnitude of the contamination was very great. We now know that our previous assumptions about the mechanisms that could lead to exposure to vapor intrusion were not complete. The result is that additional work may be required to investigate or remediate sites that are in the operational or monitoring phase, or that have already been closed. Separate ranking systems have been developed to account for the two different sources of contaminated vapors. Because we now recognize the need to take a different sampling approach, when the Department evaluates a site for vapor intrusion, both sources can now be effectively considered," according to the NYSDEC's website.

According to the DEC, the evaluation at a specific site will initially involve a review of existing environmental data to see if sufficient information is already available to assess possible vapor impacts. If a vapor intrusion problem is suspected, the DEC may recommend additional sampling, monitoring or mitigation actions. Additional sampling would be used to determine the extent of soil vapor contamination and to verify initial findings. Monitoring, or sampling on a recurring basis, is typically conducted if there is a significant potential for vapor intrusion to occur if building conditions change. Mitigation steps are intended to prevent exposures associated with soil vapor intrusion. Mitigation may include sealing cracks in the building's foundation, adjusting the building's heating, ventilation or air-conditioning system to maintain a positive pressure to prevent infiltration of subsurface vapors, or installing a sub-slab depressurization system beneath the building. In most instances, mitigation of residential structures will require a sub-slab depressurization system, according to the DEC's website.

The DEC's website further explains the testing process. "Subsurface vapor samples consist of both soil vapor samples collected from the ground away from buildings (soil gas samples) and sub-slab soil-vapor samples collected from immediately beneath the foundation or slab of a building (sub-slab samples). Indoor air samples are collected from the basement or crawlspace and from the lowest level of living space. We collect these samples primarily during the heating season, because we believe that soil vapor intrusion is most likely to occur when a building's heating system is in operation and air is being drawn into the building. Outdoor air samples are collected outside of the buildings, and are used to characterize site-specific outdoor air background conditions. The length of a soil vapor investigation will depend on the data that is collected during the investigation, and is only considered to be complete when all of the exposures and potential exposures have been addressed."