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L <br />15 <br /> <br /> Geology <br /> The quarry site and surroundings are on the Precambrian Idaho Springs <br /> Formation, mainly schists, gneiss and granite. The Idaho Springs bedrock <br /> is overlain by a thin layer of colluvium through which the bedrocks protrude <br /> in many places. A narrow strip of Quaternary alluvium lines the `.train <br />' Gulch water course. <br /> The entrance road crosses Jurassic sedimentary formations for about <br />' 1/4 mile. <br /> Nature of Impacts <br />' On Site <br />' The objective of the whole operation is to remove and utilize geological <br />bedrocks. In doing this the surficial colluvium is moved. About 60 acres <br /> of existing landfornr is or will be changed from a steep, deeply incised <br /> hillside to a pit with steep walls on two or three sides. As noted in Table 1, <br />' these changes are permanent and irreversible, <br /> Construction of haul and service roads moved surficial materials from a <br /> total of about 2 1/3 acres of hillside. As noted in Table 1, these changes <br />' will be permanent unless corrected. Correction would mean ripping the road <br /> surfaces and pulling the fill materials back into the cuts. We c<rnnot forsee <br /> in 1975 what may happen to the roads 40 or 50 years in the future. <br />' <br /> The Precambrian Idaho Springs formation of most]y metamorphosed racks <br /> contain no paleontological remains. <br />' Gff Site <br />' All the bedrock material that is hauled away will be deposited, or• used, <br />off site to surface roads or other places where vehicular or foot traffic is <br /> heavy. Such use can contribute damage to the natural environment by <br /> covering soil, hindering vegetal growth, etc. But traffic without surfacing <br />' could be equally or more damaging. Improvement in the human environment is <br /> considered to outweigh damages to the natural environment. The changes <br /> will, in a practical sense, be mostly permanent and irreversible. A <br /> +4 rating was therefore assigned as an off-site impact for "Bedroc:k and <br />' Iinerals," under "Hauling," Table 1. <br /> Future Impacts <br />' <br /> The greatest impacts on land form and surficial materials have already <br /> been experienced, but moderate changes still lie ahead. An estimated <br /> 10 to 18 additional acres of surface are scheduled for the final quarry. <br />' Future operations will be mostly downward. All foreseeable roads have <br /> been built. <br />' Bedrock and accompanying minerals will continue to be removed from <br />the site and deposited off site. That means that the impacts on bedrock, <br />both on site and off site will continue as long as the operation continues. <br />1 <br />1 <br />