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site on sediment concentrations appear to be limited to the ditch along the south side of the valley for a distance of about 2,200 feet below the area where adit discharges reach the ditch, resulting in approximately 0.75 miles of wetlands frontage subject to sediment contamination from the site. Additional receptors include the fishery present in the Swan River along the north side of the valley(CDPHE,2002). Although elevated concentrations of some metals compared to background levels have been measured in surface-water samples collected from the Swan River downstream of the site, all concentrations remain within the table-value standards for this reach of the Swan River. Fish populations are present in the Swan River from the PPE for the entire 15-mile target distance limit(Bennett,2000). The waste-rock pile and stream-side tailings are uncontained with respect to the surface- water pathway. Adit discharges flow over the waste rock and through a wetlands area prior to reaching the ditch on the south side of the Swan River valley. The fine-grained mill tailings located immediately below the former mill site have been covered in previous remedial actions,resulting in at partial control of erosion from this source. However,the cover is thin or non-existent in places and the toe of the covered material is adjacent to the floor of the valley. The waste-rock piles are well removed from the flood plain and are more likely to impact the site through erosion or overland flow during rain events rather than by direct inundation during spring runoff or flood events in the Swan River. There are no surface-water diversions on either the Blue River or Swan River that are utilized by local communities or municipal providers for drinking water(CDPHE,2002). A majority of the domestic drinking-water supplies in Summit County are obtained from shallow wells screened within the alluvial deposits associated with the Blue River (Chubrillo, 2000). 7.6 Groundwater and Air Pathway Analysis At the time of the CDPHE investigation(September 2000),CDPHE determined that the residents living at the site at the time did not use groundwater for drinking-water purposes(CDPHE,2002). In the time since that investigation,the residents have moved and there is no longer any residential use of the site. According to CDPHE (2002),groundwater in the vicinity of the iXURoyal Tiger site is used primarily by residents in the area. According to the Colorado Division of Water Resources Wells,Applications,and Permits Database,there were two wells located within a'/+-mile radius of the site in 2000. However,CDPHE was unable to locate these wells in the field. An additional 3 wells were identified within the'/<-mile to%z mile target distance from the site(CDPHE, 2002). The majority of domestic wells are situated at distances greater than 2 miles from the site(CDPHE,2002). There is no indication that the groundwater pathway from the site is complete with respect to any receptors. The stream-side tailings are uncontained with respect to the air pathway. The potential risk identified in CDPHE(2002)for site residents due to the air pathway from on-site, fine-grained tailings and waste rock was eliminated when those individuals relocated away from the IXURoyal Tiger site. 8. STREAMLINED RISK ASSESSMENT According to CDPHE(2002),the concentrations of arsenic, lead, and copper in the fine- grained tailings and waste-rock materials constitute a potential hazard to humans and wildlife coming into contact with these materials. In addition, concentrations of cadmium, tXURoyal-Tger VCUP Application-- Page 20 of 33