ARCHIVED REPORTS XR0000211 - Laserfiche WebLink

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r SECTIONSIEVEN ®neer hues enfi RIMItetiono The EPA and DTSC guidance documents for risk assessment provide a systematic means for organizing, analyzing, and presenting information on the nature and magnitude of nsks to public health, posed by chemical exposures Despite the advanced state of the current risk assessment methodology, uncertainties and limitations are inherent in the nsk assessment process The quality of available data, incomplete information about existing conditions and future circumstances, as well as other factors discussed below contribute to these uncertainties and limitations This section discusses the following sources of uncertainties and limitations associated with this risk assessment o Data 0 Chemical,fate and transport modeling ' o Receptor exposure assessment o Toxicological assessment To overcome uncertainties in the estimation of health risk and potential impacts to groundwater, conservative assumptions were used in every step of the process (exposure assumptions, toxicity assessment, fate and transport modeling, and risk characterization)so as not to underestimate site risks Because multiple conservative assumptions are used, the overall results of the assessment are more likely to overestimate than to underestimate actual site risk 7.1 DATA COLLECTION AND EVALUATION The first step taken m this risk assessment was to evaluate existing soil and groundwater sampling and analysis data from 1987 to the present This risk assessment is based on data specific to the site for soil and groundwater Sampling The data collected are subject to uncertainty associated with sampling and analysis These data are presented in other parts of this health risk assessment In the risk assessment, it was assumed that samples collected were representative of conditions to which various populations may be exposed However, the collected samples may not be completely representative due to biases in sampling and to random variability of samples In general, sampling was biased toward areas of known and suspected elevated chemical concentrations, which will lead to an overestimation of risk when these results are assumed to represent a larger area The placement of soil borings and monitoring wells was, in part, purposely biased to detect and characterize potential hot spots of soil and potential groundwater contamination based on historical site ® T 118971973000NAw=KTOMRaKwnsHOREPM DOG1&Fm8 991973ppg ism 7-1