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of = Ki /O/ _ (4.1 x 10 -6 ft /e ;) (0.017)/0.441 . <br />= 1.6 x 10 -7 ft /s <br />= 5 ft /yr <br />The concentrations shown in the 50 year column of Table 32 were <br />measured in a sample collected after 0.316 pore volumes of effluent were <br />produced from lab test CR -B. The 50 year estimate of time was calculated <br />by multiplying 0.316 by Lf /vf = 150 years. The 210 year value was <br />similarly estimated. Data from lab test CR -B were used because these <br />data showed the slower rate of decline. <br />All data necessary for the application of equation 2 have not been <br />estimated. The effect of effluent from the backfill will be greatest <br />when the stream discharge is least. Therefore, we take Qu = stream <br />discharge to be 5 cfs, equation 2 becomes: <br />C = (2.4 x 10 -6/5 Cb) <br />or <br />C = 4.8 x 10 -7 Cb <br />Equation 6 shows that the stream discharge is sufficient to dilute is <br />the effluent from the backfill to the point of non - detection. The <br />largest concentration estimated in the column effluent was 4200 mg /l for <br />total dissolved solids. Equation 6 estimates that effluent with this <br />concentration would increase the TDS concentration in the stream by 0.002 <br />mg /1. This is far below the precision and accuracy with which TDS can <br />be measured. Increases in the concentrations of all other species is <br />even smaller. <br />Should the stream discharge be 1 cfs instead of 5 cfs, the <br />increase in in- stream concentration is still far below detection levels <br />for all species. Likewise, an underestimate of the value of effluent <br />discharge by a factor of 100 would not change the conclusion that the <br />effluent will have no measurable effect on stream quality. <br />(Revised 05/11194) in <br />2.05 -73 <br />