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Jurassic-and Cretaceous-aged sediments and intruded Tertiary-age porphyry bodies <br /> (Lovering, 1935). <br /> The lXL ore body near the former Tiger Town consisted of a low-grade, massive quartz- <br /> monzonite porphyry known as the stockworks(Lovering and Goddard, 1950). Ore <br /> occurred in minute veins and thin,discontinuous seams within the extensively fractured <br /> stockworks. The rocks are highly seriticized and exhibit a micaceous luster typically <br /> associated with muscovite. Sphalerite is the most abundant ore mineral in the <br /> stoc kworks and occurs chiefly in irregular-shaped masses less than an inch in diameter <br /> scattered sparsely throughout the porphyry(Lovering, 1935). <br /> The low-lying portions of the valley are covered with quaternary alluvium and colluvium. <br /> These valley-fill deposits are approximately 50 feet thick and vary in width from 500 to <br /> 1,200 feet along the Swan River(Lovering, 1950). <br /> Terrace gravels occur almost everywhere above the channels of streams within the <br /> Breckenridge mining district. The terrace gravels average 10 to 20 feet thick,and locally <br /> reach thicknesses of 75 to 100 feet. The terrace gravels consist of well-rounded <br /> boulders and cobbles ranging up to 4 feet in diameter(Ransome, 1911). <br /> Hillside wash deposits in the area are of variable age and volume. The main feature <br /> distinguishing the hillside wash deposits from the terrace gravels is the angularity of the <br /> fragments. The ratio of large fragments to the finer-grained matrix in the hillside wash is <br /> small compared to the terrace gravels. The hillside wash is representative of the shifting <br /> of deposits by localized flooding and the downstream movement associated with gravity <br /> and other site-specific events and forces. Many of the hillside wash deposits contained <br /> residual gold and were the subject of some of the more profitable early placer mining in <br /> the district(Ransome,1911). In the vicinity of the Swan River,the hillside wash deposits <br /> rest on an uneven surface of porphyry and shale,overlying at least one thin deposit of <br /> terrace gravel. The older wash in this area has a maximum thickness ranging from 25 to <br /> 35 feet(Ransome, 1911). <br /> 6.3 Hydrogeology <br /> The two principal aquifers in the project area are: 1)an alluvial aquifer system along the <br /> main drainage channels;and 2)fractured-shale bedrock aquifers. Studies in nearby <br /> French Gulch indicate that the alluvium and the shallow fractured-bedrock aquifers are <br /> hydraulically connected and act as a single unit(CDPHE,2002). <br /> The alluvial aquifers occur within stream deposits,alluvium/colluvium, and glacial <br /> deposits. Alluvial deposits occur in the Swan River Valley,with stream deposits being <br /> continuous along the valley bottom at an estimated thickness of approximately 50 feet. <br /> Pleistocene glacial gravels are the most extensive unconsolidated deposits(Lovering, <br /> 1934). <br /> 6.4 Hydrology and Climate <br /> I <br /> Portions of the IXURoyal Tiger site,primarily the fine-grained mill tailings,are situated <br /> within the flood plain of the Swan River. The adits and waste-rock dump are well <br /> removed from the river channel and most likely lie outside the 500-year flood plain <br /> (CDPHE,2002). <br /> From the Probable Point of Entry(PPE)of site contamination,the Swan River flows 5 <br /> miles to the northwest to its confluence with the Blue River. From the confluence,the <br /> Blue River flows an additional 2 miles to the inlet of Dillon Reservoir. The standard 15- <br /> 7XURoyal Tger VCUP Application -Page 14 of 33 <br />