A PRELIMINARY ASSESSMENT OF THE NATURAL AND ANTHROPOGENIC GEOCHEMISTRY OF THE RED MOUNTAIN CREEK AND UNCOMPAHGRE RIVER WATERSHEDS: IRONTON MINING DISTRICT, CO

Red Mountain Creek and the Uncompahgre River are located in the rich mineralized San Juan Mountains of southwestern Colorado, where mining from the mid 1800s through the late 1970s occurred. Sampling of the Uncompahgre River in the late 1970s, which is downstream of five tailings ponds, showed high levels of heavy metals. It was assumed the remaining mine tailings were responsible for the high concentrations of heavy metals in the waters down-valley from the deposits. Thus, in 1983, remediation began with the use of direct re-vegetation of the deposits. This remediation was required as a result of National laws, which mandated a Remedial Action Plan (RAP) developed by the state of Colorado and the Idarado Mining Company. Interestingly, the tailings were assumed to be the sole source.

Studies over the past twenty years, have suggested for site-specific locations, the highly mineralized zones may be additional sources of inputting heavy metals into streams. We assumed that heavy metal concentrations found in the streams come from weathering of highly complex mineral assemblages, as well as from mining activities. It was our objective to establish the geochemistry in the streams in areas above and below mining activity and remediated areas and to evaluate the impact of remediation. Water quality data were collected for Aluminum (Al), Cadmium (Cd), Copper (Cu), Iron (Fe), Lead (Pb), Maganese (Mn), Zinc (Zn), and temperature, electrical conductance, pH, and dissolved oxygen.

Twenty-five samples were filtered with a 45mm membrane filter and twenty-five were left unfiltered. Samples were collected in-stream after determining the discharge of each stream. The samples were evaluated using an ANOVA analysis. It appears that minimal concentrations were significantly higher from streams on the east side compared to the west side. Analysis of discharge values suggest that the remediation does minimize heavy metal transport at high-flow levels, but does not during low flow conditions