An investigation of metal concentrations in waste rock piles, stream water, benthic macroinvertebrates, and stream bed sediments to assess long-term impacts of intermittent precipitation events in the Lefthand Creek watershed, northwestern Boulder County,

Previous studies conducted by researchers and regulators have examined the sources of metal toxicity from inactive mine sites in the Lefthand Creek watershed. To date, there have been no studies conducted to assess the effects of rain storms and rapid snow melt on stream water quality. A study of metal concentrations in waste rock piles, in the stream water, in streambed sediments, and in benthic macroinvertebrates was conducted in areas near metal sources in the Lefthand, James, and Little James Creeks. It was hypothesized that correlations exist between metal concentrations in sediments, benthic macroinvertebrates, and waste rock piles. We expected that zinc, copper, and lead would follow the patterns of speciation observed in other streams and soils. In stream water, we expected zinc to be mostly dissolved, lead mostly bound to colloids, and copper in both fractions. Prioritizations were made for remediation based on benthic macroinvertebrate and sediment metal concentrations.