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agricultural land. The railroad has no regularly scheduled <br /> traffic and appears to be infrequently travelled. Road 100 is <br /> moderately travelled by local residents accessing Highway 82 <br /> north of the Roaring Fork River. The agricultural lands are <br /> located on the north side of Road 100 and are used for livestock <br /> grazing and hay production. The railroad, Road 100, and the <br /> agricultural land are topographically lower than the site and are <br /> separated from the site by an irrigation ditch; therefore, these <br /> three areas are not expected to have an environmental impact on <br /> the subject property. <br /> 4.4 REGIONAL GEOI;OGY, HYDROGEOLOGY, AND WATER USE <br /> 4.4.1 Geology <br /> The subject site lies along the southern edge of the Roaring Fork <br /> River Valley within the Central Rocky Mountain Geologic Province. <br /> The Central Rocky Mountain Geologic Province contains a wide <br /> variety of rock types of igneous, metamorphic, and sedimentary <br /> origin. Metamorphic rocks include granite, gneiss, schist, <br /> quartzite, slate, and marble. Collectively the metamorphic rocks <br /> are termed "crystalline bedrock". The igneous rocks include <br /> recent basalt flows and older intrusive igneous rocks, such as <br /> granite porphyry. The sedimentary rocks of the region are mostly <br /> Paleozoic limestones and shales, overlain by Mesozoic sandstones <br /> and shales. Typically, bedrock of the area is overlain by a <br /> variable thickness of alluvium related to Pleistocene glacial <br /> outwash. The outwash contains abundant gravel suitable for <br /> building material and forms a solid foundation for civil <br /> structures. <br /> The Roaring Fork Valley contains thick deposits of river gravel. <br /> The gravel is mostly glacial outwash from the upper parts of the <br /> Roaring Fork Valley. At one time the Roaring Fork Valley and <br /> most of its tributaries contained sizable glaciers. There are as <br /> many as three terraces along the sides of the river valley <br /> representing three different episodes of glaciation. The <br /> terraces contain rounded cobbles and boulders of many colors, <br /> including red rocks derived from the Maroon Formation, black <br /> basalt from the volcanic hills to the north, and pale gray <br /> granite from the heart of the Sawatch Range. <br /> On the south side of the valley, just above the site, several <br /> rock outcrops were observed. These outcrops are composed of soft <br /> gray shale which are part of the Pennsylvanian Eagle Valley <br /> Evaporite Series. The evaporite series rocks can be seen <br /> interfingering with the Maroon Formation on the north side of the <br /> valley and it is assumed that they underlie the river valley. <br /> The shale outcrops observed on the hill south of the site are <br /> capped by glacial outwash gravels of pre-Bull Lake age. <br /> 15 <br />