With regard to industrial properties and brownfields clean ups, perhaps no issue clean up standard has garnered more attention and increased scrutiny than indoor air. It looks like 2012 could be the year when EPA finally updates its decade old draft guidance.
EPA never finalized its 2002 draft guidance on assessing indoor air risks ("OSWER Draft Guidance for Evaluating the Vapor Intrusion to Indoor Air Pathway from Groundwater and Soils"). The lack of official guidance has left a regulatory void regarding clean up standards. In 2009, the Inspector General sharply criticized EPA for failing to develop final guidance (IG Report). EPA responded to the IG report by promising to finalize new vapor intrusion guidance by the fall of 2012.
What is vapor intrusion?
Chemicals in soil and groundwater can volatilize into the air and come up through basements and slabs into buildings. For well over a decade, EPA has required clean up plans to include an assessment and evaluation of the risks posed by vapor intrusion into buildings.
The typical process for evaluating risk had been to plug soil and groundwater sampling data into a model ("Johnson & Ettinger Model") to predict indoor concentrations within existing and future structures at a site. If concentrations were too high in an existing building, EPA would require either additional clean up or a mitigation system (similar to a radon mitigation system) to reduce concentrations. If concentrations were too high in soil and groundwater even where no current building existed, EPA could force deed restrictions to prevent future construction in those areas of the site.
Virtually all industrial and brownfield properties have the potential to present vapor intrusion risks including current and former manufacturing and chemical processing plants, warehouses, landfills, dry cleaners, and gas stations.
Why is new guidance on vapor intrusion such a big deal?
When EPA guidance is updated, it will likely lead to more conservative assumptions. More than likely, EPA will require more data gathering beyond just simple modeling. For example, EPA already has moved toward requiring more subslab sampling to evaluate concentrations of chemicals directly beneath buildings.
Updated guidance could possibly lead EPA to re-open sites that had previously had their clean ups blessed by state or federal regulators. for example, Superfund (CERCLA) requires EPA to review site clean ups every five years. Would updated guidance require re-evaluation of these sites?
New guidance could also lead to more toxic tort litigation if plaintiffs claim prior investigations were not adequate or assumptions become more conservative. Or, it could impact development plans or financing.
EPA Release First New Guidance
In February 2012, U.S. EPA's Superfund division released a new document titled Superfund Vapor Intrusion FAQs. The new document isn't the final guidance EPA promised in response to the IG report. However, it does provide some insights into what the new guidance will look like once its released.
Using the answers to questions in the new FAQ, one can gain insights into the direction EPA likely to head with new final guidance on evaluating vapor intrusion, including the following:
- Evidence from sites since 2002 show that concentrations of pollutants in indoor air are difficult to predict by extrapolating from samples to modeling;
- EPA recommends modeling only as a way to potentially screen out a site and will be more appropriate for evaluating future buildings on-site;
- EPA will move to requiring more soil gas sampling and sub-slab sampling to determine vapor intrusion concentrations;
- More conservative assumptions are going to be built into the model which will make it much more likely a site will fail screening values (for example, EPA will incorporate an assumption that it is about 10 times more likely vapors will move into buildings from deep soil-gas;
- New screening values will be developed; and
- At CERCLA and other regulatory sites, EPA is more likely to require community involvement in sites where vapor intrusion is being studied.