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4.0 Hazard Ranking System Factors <br /> The Hazard Ranking System (HRS) is a scoring system used to assess the relative threat <br /> associated with actual or potential releases of hazardous substances from sites. It is the <br /> principal mechanism EPA uses to place sites on the National Priorities List (NPL). URS has <br /> evaluated the following HRS factors relative to this site. <br /> 4.1 Sources of Contamination <br /> The French Camp site was used as a disposal site for approximately 13,000 cubic yards of <br /> asbestos-containing pipe and other debris. Asbestos is a known human carcinogen by <br /> respiratory exposure. The asbestos-containing material (up to 70 percent chrysotile <br /> asbestos) has been capped with a 3-foot thick layer of clean fill, incorporating a steel <br /> mesh to prevent burrowing animals from bringing contaminated material to the surface <br /> (7,20). <br /> 4.2 Groundwater Pathway <br /> 4.2.1 Hydrogeologic Setting <br /> The French Camp site is located in the San Joaquin Basin Hydrologic Study Area (HSA), a <br /> 13,500-square-mile basin drained by the San Joaquin River. The HSA, an alluvial formation, <br /> is bordered on the north by the Sacramento - San Joaquin Delta, on the east by the Sierra <br /> Nevada, on the south by the Tehachapi Mountains, and on the west by the coast ranges <br /> (17). <br /> 4.2.2 Groundwater Conclusions <br /> The asbestos contained in the off-specification piping and other debris is not leachable, <br /> and thus is not available for groundwater migration. <br /> 4.3 Surface Water Pathway <br /> All of the asbestos on-site is buried beneath 3 feet of clean fill, and therefore is not <br /> available for surface water migration. <br /> i4.4 Soil Exposure and Air Pathways <br /> The capped material is not available for air dispersal; direct contact exposure with the <br /> buried material is not possible. <br /> URS Consultants, Inc. Page 15 <br />