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<br />R. G. OTTO & ASSOCIATES <br />C:~ Y <br />Results: Surface Water Assessment. Analysis of Cotter/USGS <br />surface water data took place in three steps. First, the total <br />data set~was•screened to identify parameters for which measured <br />concentrations were consistently below the analytical detection <br />limits. Parameters for which the measured concentrations were <br />below the detection limit on more than 60% of the sampling <br />occasions at site 302 (downstream of the waste rock pi.Les) and for <br />which the remainder of the (usable) data approximated this low <br />value were excluded from further consideration. Second, the <br />effects of the waste rock piles on general water quality <br />descriptors (conductivity, pH and sulfate concentration) were <br />evaluated. Finally, cross-pile changes is concentration of trace <br />'•?~ metals that were found in measurable quantities on a r~eqular basis <br />were examined. <br />Seven of the trace metals; arsenic, barium, cadmium, mercury, <br />selenium, silver and radium-228 were present at concen~brations too <br />low for assessment of waste rock pile impacts (Table 4). All were <br />present at concentrations below or approximating the d~atectioa <br />limit in most of the samples collected both above and :oelow the <br />waste rock piles. None indicated any form of net incz~aase in <br />concentration across the waste piles (i.e. below detecttioa limit <br />above piles, measurable at low concentration below). [t is clear <br />that runoff or seepage from the piles is having no sig»ificant <br />influence, if any, on stream quality for these paramet~ars. <br />"~.:~ <br />29 <br />