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SAFEWAY MEAT PACKING FACILITY, STOCKTON, CALIFORNIA TIER III RIsK BASED CORRECTIVE ACTION FEBRUARY 26, 1996 PAGE 1 - 2 and the environment This later objective is the primary goal for the Stockton Meat Packing Plant risk assessment Each Risk assessment involves five major steps • First, chemicals of interest (COIs) are identified among all of the chemicals that are known or suspected to be found in the soil and water This is done to focus the other portions of the risk assessment on those chemicals that have the greatest potential to threaten public health, the environment, and groundwater quality • Second, a risk assessment identifies how a person may contact a COI (this step is call the exposure pathway analysis) The potential for an individual to be exposed to a chemical is the result of the activities of the individual, the distribution of the chemical in the soil and groundwater, the conditions of the site (e g , the presence of a drinking water welI), and the fate and transport of the chemical through the environment When an individual is in contact with a chemical (e g , drinking water from a well that is screened within a groundwater plume) the exposure pathway is "complete " A "potentially complete" pathway is one that may not actual occur but can reasonable expect to exist if conditions change (e g , a chemical in groundwater can migrate from a source area to drinking water well) An "incomplete" pathway is a pathway that does not occur nor can reasonably be expected to occur (e g , inhalation of vapors from most metals is incomplete since metals are generally not volatile) Incomplete pathways are not evaluated quantitatively in a risk assessment • Third, for all complete or potentially complete exposure pathways, an individual's daily "dose" of a chemical is estimated This is involves estimating the average or representative concentration of the COI in the environment and characterizing the frequency and magnitude of an individual's contact with a chemical (e g , how many days per year an individual drinks water from an impacted well and much well water is consumed each day) • Fourth, the toxicity of each COI is identified Health end points of concern are either carcinogenic or noncarcmogenrc Both Federal and State regulatory agencies develop toxicity factors to be used in risk assessments Risk assessments are based on the theory that any exposure to a carcinogeruc chemical results in an 0131CDJ1