Hazardous Ranking System in the United States

Hazardous Ranking System (HRS) in Environmental Law

The method used by the Environmental Protection Agency (EPA) to evaluate the dangers posed at a site where hazardous waste has been disposed. The system is spelled out in the regulations, and it is amended from time to time. The evaluation is designed to help the agency decide which sites should be placed on the National Priority List, the list of Superfund sites. If a site is on the list, the EPA may use federal funds if necessary to eliminate a threat to health or the environment. If a site is not on the list, use of federal funds is severely limited.

General Concepts in the HRS

Throughout the ranking process, the EPA’s purpose is to determine the likelihood of exposure to or release of hazardous substances and the type of threat the site poses. The EPA determines the score or rank by looking at four different pathways for release: soil, air, groundwater, and surface water. Its evaluation includes some common elements for all four pathways.

First, the source of the danger is considered. The agency must identify the hazardous substances available to the various pathways, the sources at the site, and overall contamination. Second, the likelihood of release or exposure is evaluated, including contamination that has been observed and, if no release has occurred, the potential for contamination or release. Movement of hazardous substances is also considered. The EPA must find answers to a number of questions: What is the possibility of a hazardous substance being leached from the soil into groundwater or running off into surface water? How certain is the movement of contamination from groundwater to surface water? This sort of inquiry will focus on the hydrogeology of the area, the soil type, and other relevant factors. Third, waste characteristics are rated. Toxicity, mobility, quantity, and persistence are considered in this calculation, along with the likelihood that the substance will accumulate in organisms.

Finally, the targets are scored. This element considers the likelihood that the community will be exposed to the contaminants. For example, the population may be exposed to the hazardous substance because it uses an impacted aquifer as a source of drinking water. Some soils conduct contamination more quickly than others because they are more porous. These and similar factors increase the public risk.

How the System Works

The EPA comes into the picture when a person or a state notifies it that hazardous substances may have been disposed of at a particular site. An investigation follows, usually in the form of a preliminary assessment. If the preliminary assessment shows a possible release or threat of release, a site inspection will generally be conducted. If the agency determines that the site may pose a risk, it may move the site to the ranking process. However, the EPA may act immediately if the dangers appear imminent.

Once the site is being evaluated, the regulations are quite specific about how the scores are to be calculated. The person working on the ranking will consider numerous factors for each pathway, resulting in a number for that pathway. Then the total score is calculated using a formula: the sum of the squares of each pathway score divided by four. The result will range between 0 and 100. If the score is high enough, the site is proposed for inclusion on the National Priority List. If it is not, the site may be listed by the state, but it will not be eligible for a federal remedial action unless the state names the site as its first priority for cleanup.
Based on “Environment and the Law. A Dictionary”.