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<br />90 <br />100 <br />0.074 <br /> <br />, RETI'INED <br /> <br />u. S. Sieve Series <br />40 30 <br /> <br />10 <br /> <br />~ PASSING <br /> <br />~4 ~" 3/8"~" 3/4"1" 1~" 3" <br />100 <br /> <br />90 <br /> <br />'200 100 <br />o <br /> <br />10 <br /> <br />20 <br /> <br /> <br />30 <br />40 <br /> <br />so <br /> <br />60 <br /> <br />70 <br /> <br />80 <br /> <br />0.147 <br /> <br />2.U <br /> <br />4.7 <br /> <br />0.589 <br /> <br />Sieve Size, rml . <br />Grain size distribution curves for eight Broadway a'luvlum samples <br />Piney Creek alluvium samples (dotted curves). <br /> <br />After Turner (1974) <br /> <br />(solid curves) and <br /> <br />GRAIN SIZES OF ALLUVIUM <br /> <br />Henderson to Brighton, Colorado <br /> <br />VII-7 <br /> <br />extractable cubic yards of aggregate amount to 73,000,000 cubic yards per <br />mile of river valley. <br /> <br />Turner (1974) has estimated that due to various land use constraints, such <br />as urban development, extraction of the reserves will be limited to about <br />two thirds of the potentially extractable quantities, or roughly 50,000,000 <br />cubic yards per mile of river valley, based on the Brighton quadrangle map <br />detai 1 ed study. <br /> <br />INVENTORY OF SAND AND GRAVEL MINING ACTIVITIES <br />Data and records were searched from the Colorado Geologica] Survey, the <br />Adams County Planning Department and the Colorado Rock Products Associa- <br />tion. <br /> <br />80 <br /> <br />70 <br />60 <br /> <br />The South Platte River corridor through Adams County is one of the last <br />large remaining Denver metropolitan area sources for gravel, according to <br />the Colorado Geological Survey. The entire alluvial fIoodplain of the South <br />Platte River through Adams County is comprised of sand and gravel suitable <br />and desirable for mineral extraction. These South Platte River corridor <br />resources range up to 70 feet in depth, and average two miles in width along <br />the river in Adams County. Table VII-2 provides a summary of the sand and <br />gravel mining activities. <br /> <br />so <br /> <br />40 <br /> <br />30 <br /> <br />20 <br /> <br />10 <br />o <br /> <br />A considerable amount of the Adams County sand and gravel is currently con- <br />trolled by operating sand and gravel mining companies which plan to extract <br />the resources through the year 2000. Current Adams County ownership is <br />shown in Figure VII-I. <br /> <br />Major sand and gravel companies operating along the South Platte River <br />include Cooley Sand and Gravel Company, Brannan, Western Paving, Mobile <br />Pre-Mix, Suburban Sand and Gravel, Kilgroe-Atchison, Adams Aggregate, and <br />Aggregate Resources. <br /> <br />FIGURE VII-4 <br />