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2.0 METHODS AND MATERIALS <br />•~ <br />2.1 Chemical and Physical Parameters <br />Three stations were established in the Williams Fork River near <br />Craig, Colorado to monitor selected chemical/physical parameters. <br />Station 1 was located approximately 950 m upstream from the coal silo; <br />Station 2 was situated approximately 30 m below the silo; and Station 3 <br />was located about 1600 m downstream from the silo (figure 1). <br />Selected chemical parameters were measured is the Williams Fork <br />River oa March 27, Juae 30, September 24, and November 5, 1980 (Table 1). <br />Dissolved oxygen, conductivity, and pH were measured in the field between <br />1300 hr and 1600 hr. Analytical procedures followed techniques presented <br />is "Standard Methods for the Examination of Water and Wastewater" (American <br />Public Health Association et al. 1975). Dissolved oxygen concentrations <br />were determined by the polarographic method which utilizes a YSI 54RC <br />dissolved oxygen meter and associated probe. Hydrogen ion concentrations <br />(pH) were measured with a Corning portable pH meter, Model 610A. Conductivity <br />--~ <br />was measured with a YSI Model 33 meter, while turbidity was measured is !i <br />the laboratory using a Hach turbidimeter. <br />Physical characteristics observed at each station included temperature, <br />depth, river width, flow, and substrate type. Flow was estimated by <br />floating limes along a 20-foot transect. Five time trials were repeated <br />per station with results presented in meters/second (m/s). <br />2.2 Benthic Macroinvertebrates <br />Four replicate Surber samples, each representing an area of 1 ft2 <br />(0.093 m2), were collected at Stations 1, 2, and 3 in the Williams Fork <br />River on March 27, Juae 30, September 24, and November 5, 1980. The <br />Surber sampler was firmly seated oa the substrate with the net trailing <br />downstream. All stone and debris is the quadrat were scraped in the <br />mouth of the net. After the coarse material was cleaned and discarded, <br />the area within the frame was thoroughly stirred with a stick to the <br />maximum possible depth to dislodge the animals inhabiting interstitial <br />spaces. The contents of the net were emptied into a plastic pail filled <br />-- with sieved water. The contents of the pail were stirred and slowly <br />poured through a No. 30 sieve. The pail was refilled and the process <br />2 <br />