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<br />- 20 - <br /> <br />median discharge was used to calculate weight flow rates in Table X for <br />Station US-6, Cycle II. <br /> <br />With these considerations in mind, examination of Table X reveals <br />several interesting occurrences. There is a gradual buildup of dissolved <br />radium-226 and uranium between the point sampled farthest upstream on the <br />Dolores River and the point on the Dolores just above the mouth of the San <br />Miguel. There is a similar increase on the San Miguel River from the point <br />just upstream from Uravan to the sample point l.6 miles downstream from <br />Uravan. On the basis of the figures in Table X, it is not possible to attri- <br />bute all the noted increase in the San Miguel River to waste discharges from <br />Uravan mill. For instance, in Cycle I when stream flows were relatively <br />constant, there was an increase of 190 ~g/day of radium-226 in the river as it <br />passed Uravan mill, based on streamflow calculations. Based on estimates of <br />waste discharge, the average contribution of radium-226 from the mill was a <br />maximum of l2.8 ~g/day. This is similar to the results having to do with <br />sulfate in the mill discharge as noted on page l4. No present means has been <br />found to reconcile this discrepancy. <br /> <br />As done above for sodium and chloride, an attempt was made to strike <br />material balances for radium-226 and uranium around the confluence of the two <br />rivers. The radium-226 balances do not agree within themselves for either <br />cycle. During Cycle I, the average inflow to the confluence (Stations US-6 <br />and US-13) was 880 ~g/day, the average outflow at Station US-l4 was 1670 <br />~g/day. For Cycle II, the corresponding inflow and outflow were 2660 ~g/day <br />and 1210 ~g/day. These differences remain to be explained. <br /> <br />The uranium balance for Cycle I showed good agreement, with 3 percent <br />less outflow than inflow. Agreement on the second cycle balance, however, was <br />only within 45 percent; it is felt that the weight outflow (Station US-14, <br />Cycle II) is not completely consistent with corresponding weight flow rates <br />calculated for sampling stations farther down the Dolores River. <br /> <br />If the flow of the Dolores River above the mouth of the San Miguel <br />River is disregarded temporarily, it is seen that there was a steady reduction <br />in the weight of dissolved uranium passing each sampling point beginning just <br />below Uravan mill (12,420 gm/day, Cycle I) and continuing to the mouth of the <br />Dolores River (6770 gm/day, Cycle I). This holds with consistency for both <br />cycles. In each case, the weight of uranium remaining dissolved at the mouth <br />of the Dolores River was about 55 percent of the weight of dissolved uranium <br />passing the sampling point just below Uravan mill. There was a reduction from <br />the weight of dissolved radium-226 passing just below Uravan to the similar <br />weight at the mouth of the San Miguel River. This was probably due to some <br />interaction of radium-226 with the precipitation process occurring in this <br />reach of the river. The steady decrease in the weight of dissolved uranium <br />passing consecutive sampling points downstream from Uravan mill is not noted <br />with the remainder of the stations for dissolved radium-226. The weight of <br />dissolved radium-226 passing downstream fluctuates from station to station on <br />the main stem of the Dolores River below the mouth of the San Miguel; there <br />is no consistent trend. However, in each cycle, the weight of dissolved radium- <br />226 passing the mouth of the Dolores River was 65 percent higher than the <br />cor~esponding weight passing the. sampling station 1.6 miles below Uravan mill. <br />