In February and June unfiltered water samples were collected at all sites for analysis of Hg and 30 other elements using an ultraclean sampling protocol (40). Hg samples were acidified 500:1 with concentrated trace metalgrade HCl. For other elements, 250-mL samples were acidified with 0.5 mL of grade HCl. For other elements, 250-mL samples were acidified with 0.5 mL of optima grade nitric acid. Duplicates, a trip blank, and six field blanks were included in both winter and summer sampling campaigns. Oil sands sampling is described in (13).