Since the 1990s, the Maine DEP has relied on two cleanup guidelines for contaminated soil: 1) the Remedial Action Guidelines (commonly referred to as the RAGs), and 2) the Procedural Guidelines For Remediation Of Oil Contaminated Soil (until recently referred to as the Decision Tree). The RAGs target non-petroleum contaminants such as heavy metals and solvents, while the Decision Tree address petroleum releases such as gasoline or fuel oil.
The RAGs are based on the risk posed to human health through ingestion, or inhalation of, or skin contact with the contaminant. Because the risk will vary depending on the setting (e.g., a residence compared to a factory), the DEP established guidelines for Residential, Adult Worker, and Trespasser settings, with the Residential being the most stringent and the Trespasser the least stringent. The RAGs also have a category for ground water leaching, that is, the likelihood that a contaminant in soil will leach ground water.
In contrast to the RAGs, the Decision Tree guidelines are based only on the potential for oil to leach into ground water, and to a lesser degree, address the risk posed by petroleum vapors from inhalation or explosion. The Decision Tree does not include cleanup guidelines based on contact with or ingestion of oil-contaminated soil.
It is notable that none of these standards are in statute or regulation – they are simply guidelines. Depending on one’s perspective, their guideline status can be viewed as a benefit because of the regulatory flexibility it provides, or a detriment because the cleanup goal can not always be easily predicted.
The Maine DEP is in the process of revising all soil cleanup standards so that both petroleum and non-petroleum contaminants are treated similarly, i.e., the risk posed by inhalation, ingestion, contact, vapor, and ground water leaching will be assessed for each. For petroleum, the DEP plans to switch from using the Diesel Range Organics (DRO) and Gasoline Range Organics (GRO) laboratory tests to the more sophisticated Volatile Petroleum Hydrocarbon (VPH) and Extractable Petroleum Hydrocarbon (EPH) methods. Finally, the DEP intends to replace the old risk settings with Residential, Commercial Worker, Construction Worker, and Recreational User.
The DEP released draft cleanup guidelines in late July 2009 including a revised version of the Human Health Risk Assessment basis document. St.Germain will keep you informed as to their status.