Risk Assessment

The four stages of risk assessment for hazardous waste sites are hazard identification, exposure assessment, toxicity assessment, and risk characterization. There really is not just one stage that interests me the most. The process as a whole is very interesting. I am the lab manager at US Ecology Nevada, a hazardous waste disposal facility, where hazardous waste will ultimately go should it need to be removed and possibly treated. Working on the disposal end I am not exposed to the processes used to determine which contaminants are stressed for concern, which populations are potentially at risk for contaminants, how toxic the the contaminants are for human health and welfare, and the calculations of risks for all scenerios.
US Ecology accepts many different types of wastes ranging from outdated chemicals to industrial hazardous waste to large contaminated sites that are now declared Superfund sites. It is the Superfund sites that interests me. How it is determined which contaminants will be treated for, how big of an area will be treated, and how the treatment, clean-up, will be handled. Will the waste be remediated or must it be removed and disposed of in a proper landfill? These are questions I have always wondered about.
The EPA website explains in detail about the process for sites to be declared Superfund sites. The Hazard Ranking System, HRS, is interesting to me. This is the process of how potential sites are listed on the National Priority List, NPL, after a petition has been submitted to the EPA by the concerned public. The HRS uses a numerical screening system that assigns numbers to risks associated with the site. These are grouped into three catagories the potential for hazardous substances to be released into the environment, waste characterization, and who or what is affected by the release of hazardous substances. A site may score high or low depending on the seriousness of the associated risks. The HRS score does not determine the priority level of the site on the NPL, more in depth studies are required for a priority level to be assigned. This is just a small sample of what is needed for a site to be declared a Superfund site. More information is available at http://www.epa.gov/superfund/index.htm.