Paper No. 15-4
Presentation Time: 8:30 AM-4:30 PM
SURFACE MOBILITY OF HEAVY METALS IN SOIL FROM HISTORIC MINE WASTE PILES IN THE CARDIFF TRAIL AREA, ALTA, UTAH
Little Cottonwood Creek is impaired for cadmium, copper, and zinc per the Clean Water Act (UDWQ, 2016). Historic mine waste piles up slope of the town of Alta in Little Cottonwood Canyon contain heavy metals in unknown quantities with unknown mobility that may impact Little Cottonwood Creek. This study aims to determine the concentration of heavy metals in soil and the mobility from the waste piles in the Cardiff trail area north of Alta. Soil samples (n=74) were collected on, and below mine waste piles, as well as in gullies to measure the mobility of metals from erosion. Samples were also collected above waste piles and in other non-affected areas as a background concentration reference. Samples were analyzed with a XL2 Niton x-ray fluorescence meter per EPA Method 6200. Cadmium was detected in 15 of 74 samples (33 to 128 ppm) and 3 samples exceeded the BLM soil standard for camper. The average concentration of cadmium on waste piles was 34 ppm; the average below waste piles was 8 ppm; no cadmium was detected in background samples. Copper was detected in 72 of 74 samples (37 to 11,940 ppm) and 5 samples exceeded the BLM standard. The average concentration for copper on waste piles was 1543 ppm; the average below of the waste piles was 783 ppm; the average background concentration was 127 ppm. Zinc was detected in all 74 samples (111 to 15637 ppm) and none exceeded the BLM standard. The average concentration of zinc on waste piles was 4388 ppm; the average below waste piles was 1716 ppm; the average background concentration was 397 ppm. In addition, high levels of lead and arsenic were detected. Lead exceeded BLM criteria in 31 of 72 samples (102 to 29,803 ppm). The average lead concentration on waste piles was 9813 ppm; the average below waste piles was 1798 ppm; the background concentration was 444 ppm. Arsenic exceeded BLM criteria in 68 of 74 samples (23 to 4,472 ppm). Average concentrations of arsenic on waste piles was 1661 ppm; average below waste piles was 272 ppm; the average background concentration was 53 ppm. The average concentrations of all target elements are higher in samples taken below waste piles than concentrations in background samples, indicating that the metals on the waste piles are moving downslope toward Little Cottonwood Creek. Additional analysis is currently being conducted to determine the degree of surface mobility.