So, who is responsible for mitigating this soil vapor intrusion? The New York State Department of Environmental Conservation (DEC) describes the conditions under which the state will conduct the vapor intrusion evaluations and the order in which the sites will be assessed. If exposures represent a concern due to indoor sources, then the state will provide guidance to the property owner and/or tenant on ways to reduce their exposure. If exposures represent a concern due to outdoor sources, then DEC will decide who is responsible for further investigation and any necessary remediation. Depending upon the outdoor source, this responsibility may or may not fall upon the party conducting the soil vapor intrusion investigation.
At sites where there are ongoing investigations, DEC will evaluate the vapor intrusion pathway as part of the remedial investigation. At sites where remedial decisions already have been made but which do not address vapor intrusion, DEC and DOH will seek to have the responsible party conduct vapor intrusion studies. If the responsible party is unwilling or unable to conduct an evaluation, or there is no responsible party to do so, DEC will use the criteria to rank the site for the likelihood of current of potential exposures.
DEC will initially review the existing data to determine if information is available to assess vapor impacts. If a problem is suspected, DEC may recommend additional sampling, monitoring or mitigation actions. Mitigation steps are intended to prevent exposures associated with soil vapor intrusion.
Mitigation measures may include:
- Sealing cracks in building foundations
- Adjusting the building's heating, ventilation or A/C system to maintain positive pressure to prevent infiltration or
• Installing a sub-slab depressurization system prevent vapor intrusion and subsequent human exposures
The decision to install sub-slab depressurization systems at structures where volatile chemicals are detected is made on a site-specific basis with many factors considered.