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. 002912. . . . . . . . . . . However, except for aluminum, these metals were found in only very trace amounts, with the maximum average concentrations reported as follows: cadmium, 12 \lg/l at YC-3; lead, 10 \lg/l at W.R-l; and silver, 5 \lg/l at WR-2 and YC-3. 2. Mean concentrations of aluminum and iron ranged as high as 9780 \lg/l and 12,500 \lg/l, respectively, in the lower White River drainage at Rangely. As shown in the profiles in Figs. 12 and 14, these concentrations were measured during Spring runoff when sus- pended sediment concentrations were also high. The recommended EPA criteria of 5000 \lg/l for aluminum was exceeded at only one location (RM 78.2) whereas the proposed Colorado standard of 100 \lg/l was exceeded at most locations. The proposed Colorado standard for iron (500 \lg/l) was exceeded at 15 of the 19 sampling sites, as shown in Fig. 14. 3. The criteria/standard concentrations for three metals (copper, manganese, and molybdenum) were exceeded at only one station each. Yellow Creek contained mean concentrations of molybdenum which were approximately four times above the criterion of 10 \lg/l, while the White River near Rangely (RM 78.2) contained concentrations of copper (20 \lg/l - Fig. 13) and manganese (295 \lg/l - Fig. 15) in excess of the criteria/standard limits of 10 \lg/l and 200 \lg/l, respectively. 4. Selenium concentrations in excess of the criteria/standard value of 10 \lg/l were measured in Yellow Creek and Little Beaver Creek. The selenium concentrations in these streams averaged 16 \lg/l during "low flow" at YC-3 and 25 \lgll during "high flow" at LBC-9. 5. Measurements for zinc at the 17 stations in the White River drainage indi cated that 8 stations had mean concentrations in excess of the proposed standard value at the measured water hardness (the pro- posed zinc standards are a function of water hardness, CDH, 1976). As shown in Fig. 16, zinc concentrations were generally higher during "low flow" with the highest concentration (100 \lg/l) reported near the headwaters of the White River at RM 187.1. 6. Mean concentrations of chromium were all less than 20 \lg/l, which is significantly less than the criteria/standard limit of 50 \lg/l. 7. The arsenic standard of 10 \lg/l proposed by Colorado was equaled at the Yellow Creek station, but all other stations reported mean arsenic concentrations less than 10 \lg/l. 8. Mean concentrations of total metals at the two sample stations in the Milk Creek drainage were above the criteria/standard levels for only iron and aluminum (Figs. 12 and 14). As was true for stations in the White River drainage, concentrations of these metals were highest during Spring runoff when the suspended solids load was quite high. 38 L ,