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in Jefferson County. Although the coal mined in the basin is inferior in <br />quality to that from other fields in Colorado, it meets with a ready sale <br />due to the nearness of the city of Denver and a region of intense farming. <br />Precious metals are not found in the basin, although there are numerous <br />gold and silver mines in the Clear Creek basin immediately to the north. <br />The discovery of gold in the latter basin in 1959 followed by a develop- <br />ment of gold and silver mining, resulted in the initial development of <br />the Dear Creek 3asin, as it was on the shortest route from the mining <br />area to Denver. <br />12, Soils,- The soils of the basin are composed largely of andes <br />itic debris, derived principally from granite and gneiss. The soils <br />derived from granite are very permeable, gravelly sandy loans, and occur, <br />for the most part, on steep slopes among frequent outcrops of granite. <br />This type of soil is subject to rapid erosion when either the forest or <br />grass cover is materially disturbed. The soils derived from gneiss range <br />from permeable, gravelly, fine sandy loams to loams high in organic <br />matter. All the soils in the basin contain large numbers of angular <br />gravel fragments which have a tendency to form an erosion pavement with a <br />resulting reduction in both run-off and erosion.. ITherever the topography <br />is suitable for farming, the soils are very productive, <br />13. Bank erosion and silt.- No silt samples have been taken in <br />Bear Creek. Normally the creek does not carry a great deal of silt, but <br />during periods of high water an excessive amount of silt and debris is <br />carried and irrigation ditches are subject to silting. <br />14. Due to the steep gradients, bank erosion has been excessive, <br />particularly during .floods, when highway fills are eroded rapidly and the <br />boulders are rolled downstream by the force of the water to eventually <br />clog the streambed or be deposited on adjacent lowlands. Highways <br />bordering on the stream have, in places, been completely washed out, and <br />the resulting debris has filled up downstream channels to depths reported <br />to be from 10 to 12 feet, <br />5- <br />