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<br />' wrn Sundry and Sundry Adru OMO FirinyrioNSuwemy <br />' 3.1.2 Conceptual Model Formulation <br />' Based on a review of existing data, a conceptual model of the sites which identifies potential or <br />' suspected sources of contamination, types and concentrations of contaminants detected at the sites, <br />potentially contaminated media, and potential exposure pathway, including receptors was <br />formulated. Figure 3 is a ci~py of Exhibit 4-1 from RAGS I. Details concerning development <br />of a conceptual model aze provided in the data quality objective (DQO) guidance (EPA 1987a,b) <br />' and RI/FS guidance (EPA 1!~88a). Figures 4 and 5 aze conceptual site models used to illustrate <br />the potential exposure pathways discussed in this evaluation for human and ecological receptors, <br />' respectively. The conceptual models aze used in the following subsections to systematically <br />address the potential risk to humans and ecological receptors due to these mine properties. <br />3.1.3 Soutces <br />1 <br />Source variables are designated chemicals defined as "toxic or acid-forming materials" or <br />materials which would produce acid mine drainage. The rocks in which low-grade ores occur <br />aze not sulfates and not acid~•producing. <br />The rocks contain low levels of naturally-occurring uranium; but field data collected using <br />scintillometers showed radio~ictivity levels in waste rock storage piles three or four times lower <br />than that occurring on a local outcrop, which outcrop is tygical of numerous such features in the <br />immediate area (see Attachment 1). Therefore, if the waste rock at the Sunday and West Sunday <br />Mines was considered a source of uranium metal, the naturally-occurring rocks on outcrop in the <br />' same azea could be considered sources, with appazently greater concentrations of uranium or other <br />radioactive elements. Uranium, rather than being a contaminant, is actually a ubiquitous element <br />' which occurs naturally in this mining region, and which is associated with Soil type 60, mapped <br />on Exhibit I-2 in the Mine Pe.mut. Soil type 60 (Gaynor-Sixmile bouldery clay loam), discussed <br />' H\USEASUffAf~WWAl0.LLETIFAS.9f\WSUNSUN Rlr <br />Page 13 <br />1 <br /> <br />