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<br />w <br />..,J <br />N <br />ClC <br /> <br />CHAPTER 2 <br /> <br />LABORATORY INVESTIGATIONS <br /> <br />Three laboratory tests were designed to isolate the effects <br /> <br />of velocity, sediment concentration, dilution, exposed surface area, <br /> <br />extended contact time and agitation on solute concentration in flow <br /> <br />over Mancos Shale. In the first experiment, a specially designed <br /> <br />apparatus was used to relate solute concentration to carefully <br /> <br />controlled flow rates, The rate of dissOlution was observed with <br /> <br />standing water, a slow rate of flow (before incipient motion) and at <br /> <br />rates which produced sediment transport, These conditions were <br /> <br />repeated for weathered and unweathered samples. The unweathered <br /> <br />shale was grouped into two sizes. <br /> <br />A second experiment using a simple jar test was conducted to observe <br /> <br />the effects of dilution, agitation and contact time on EC values. For <br /> <br />the third laboratory experiment, simulation was conducted over a bed <br /> <br />of Mancos Shale using artificial rainfall in a tilting flume. <br /> <br />Velocity, total solute concentration and total sediment concentration <br /> <br />were measured for runoff over weathered Mancos Shale. <br /> <br />Soil description. The Mancos Shale used in all the experiments <br /> <br />is from the Grand Valley near Fruita, Colorado. Two layers were <br /> <br />removed. The upper weathered portion was approximately five inches <br /> <br />deep. The second, unweathered sample of shale was taken from a <br /> <br />depth of 5-12 inches below the surface. Table 2.1 lists the character- <br /> <br />istics of the shale, <br /> <br />The shale samples were greatly disturbed in the removal process <br /> <br />and in placement for the experiments, The shale was wet I,hen <br /> <br />removed from the field. It was dried before storage. <br /> <br />I; <br />