GOLD KING MINE SPILL: EFFECTS ON THE WATER AND SEDIMENT QUALITY IN THE ANIMAS RIVER

During an investigation of the Gold King Mine near Silverton, Colorado, 3 million gallons of mine wastewater were released into Cement Creek, a tributary of the Animas River. The contaminated wastewater and sediment flowed downstream into the San Juan River and continued into the Colorado River. Historic mines like the Gold King pose a threat to the water quality and environmental health of the surrounding and downstream areas due to the metals and contaminants constantly discharged from the mines, their tailings, and waste rock piles. The torrent of wastewater, which the EPA reported contained arsenic, cadmium, lead, and mercury, deposited fine orange sediment up to 50 miles downstream. We collected water and sediment samples from twelve locations along the banks of the San Juan River, Animas River, and Cement Creek one week after the spill, and then returned and collected again 9 and 11 months later. Water samples were analyzed for cations and anions (IC), trace elements (ICPMS), and alkalinity (titration). We subsequently performed sequential leaching experiments and the EPA’s Synthetic Precipitation Leaching Procedure (Method 1312) on the sediment collected. Leachate from these experiments has been analyzed for trace metals using ICPMS. Additionally, the mineralogy of the sediment was determined with XRD. This investigation revealed high levels of trace elements in Cement Creek one week after the spill (Zn concentration was 3593-6781 ppb, while Cu was 423-811 ppb). Concentrations of these trace elements remained elevated as Cement Creek converged with the Animas and San Juan Rivers, relative to the upstream waters. The sediment collected one week after the spill revealed high concentrations of metals from the spill site downstream 51 km to Durango, CO at which point the concentrations decreased. The results will be compared with the 9-month and 11-month water and sediment leaching samples. The results from this investigation will help determine long-term implications of the spill, while the leaching experiments will reveal how the sediment will behave in the environment after deposition, as well as the mobility of contaminants from the sediment.