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<br />The upper most part of the basin is made up of volcanic and sedimentary rocks <br /> <br />and deposits of tertiary and quaternary age, which contain few readily soluble <br /> <br />minerals. A geology map of this area is attached on page 4. The lower Fremont <br /> <br />River and the middle and lower Muddy Creek flow through a variety of sedimen- <br /> <br />tary rock formations ranging ln age from Cretaceous to Permian. The shale mem- <br /> <br />bers of the Cretaceous Age Mancos Shale and the Jurassic Age Carmel Formation <br /> <br />are believed to be the major contributors of dissolved solids. <br /> <br />PROBLEM <br /> <br />Total dissolved solids contributed by the Dirty Devil basin are estimated at <br /> <br />about 125,000 tons annually. Total dissolved solids concentrations in Dirty <br /> <br />Devil River flows range from 1,000 to 5,000 mg/L. Soils that have been derived <br /> <br />from gypsum-bearing marine shales (Mancos) is one of the maln sources of salt <br /> <br />ln the basin. Irrigation return flows and natural runoff from precipitation <br /> <br />provide the vehicle for carrYlng this source of salt into the river. Several <br /> <br />highly saline sprlngs (7,000 to 30,000 mg/L TDS) also contribute salt to the <br /> <br />rlver system. The spring areas appear to be associated with the Carmel <br /> <br />Formation. <br /> <br />The objectives of this study are to identify areas of salt loading within the <br /> <br />Dirty Devil River Basin, to determine the quantity of salt being contributed by <br /> <br />each area, and the salt loading mechanisms, and to develop comparable control <br /> <br />alternatives. <br /> <br />C"r,4"'9 <br />:ll~ ,; <br /> <br />(3) <br />