WSP09832

• File Number: 8220.114.J
• Description: Dolores Participating Project
• State: CO
• Basin: San Juan/Dolores
• Water Division: 7
• Date: 8/1/1960
• Author: USDOH Ed. & Welfare
• Title: Stream Surveys in Vicinity of Uranium Mills - III. Area of Uravan-Slick Rock-and Gateway Colorado - August 1960
• Water Supply Pro - Doc Type: Report/Study

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and lower chloride concentration of the San Miguel River, an arithmetic average
of 415 mg/l rise was noted in the chloride level of the combined stream (Station
US-14) as compared to the chloride level of the San Miguel River before mixing.
By contrast, the arithmetic average rise of chloride concentration in the San
Miguel River as it passed Uravan was 123 mg/l.

Sodium and chloride balances made around the confluence of the Dolores and
San Miguel Rivers gave excellent agreement for cycle I. For example, a total of
106,400 pounds/day of chlorides were found above the confluence (Stations DS-6 and
US-13), while 110,400 pounds/day were found below the confluence. This agreement
within five percent tends to show the consistency of the respective laboratory
analyses.

On the other hand, two considerations apparently affect the striking of a
similar material balance around the confluence during cycle II. Rain during the
second cycle resulted in a wide range of flow at Station US-6, as seen in Table
III. Using the average flow given there of 23 cfs, the resulting material balance
for chloride shows 666,000 pounds/day above the confluence against 196,000 pounds/
day below as measured at Station US-14. An attempt was made to reconcile this dif-
ference by assuming the median flow for Station US-6, cycle II, to have been more
representative of flow conditions during the sampling period. This attempt gave a
value of 296,000 pounds/day of chlorides above the confluence compared to the
196,000 pounds/day below. This is not a satisfactory agreement. It is felt that
neither the sample taken nor the flow averages used is truly representative of
river conditions caused by the intense rain. The other factor that may affect
these results is not seen directly in these figures themselves. Station US-14 is
located twelve miles downriver from the confluence of the Dolores and San Miguel.
It seems likely that various chemical constituents could be leached from the soil
and carried away in the runoff from a heavy rain, thus affecting the concentration
measured in a composite sample of the kind that was taken from the river during
this survey.

Here, as in the Slick Rock area (Dolores River), all sulfate and total
dissolved solids concentrations in river samples were above recommended limits in
the U. S. Public Health Service Drinking Water Standards.

Radiological

Most of the radium-226 analyses were performed by a private laboratory; the
remaining radium-226 and all the uranium analyses were done by colorado River Basin
Project personnel at the Public Health Service Occupational Health Field Station
in Salt Lake City. Gross radioactivity analyses were carried out by the Field
Operations Section, Robert A. Taft Sanitary Engineering Center.

Data from radium-226 and uranium analyses of stream and effluent samples are
presented in Tables VIII and IX. Generally, levels of both radium-226 and uranium
are higher in the samples taken during cycle II than in those taken during cycle I.
For instance, in the San Miguel River above Uravan, the dissolved radium concen-
trations were 1.6 and 0.3 ~~g/l for cycle II and cycle I respectively; corresponding
dissolved uranium concentrations were 7.9 and 6.5 ~g/l. Calculated ratios of dis-
solved radium~226, cycle II, to dissolved radium-226, cycle I, in the stream samples
ranged, with one exception, from 1.1:1 to 1.6:1. Corresponding values for dissolved