An abandoned structure and waste-rock pile from the Silverledge Mine adjacent to Mineral Creek, Colo.

A site of continuous water-quality sampling during a tracer test conducted on the North Fork of the Animas River, Colo.

View of a data logger used to control a pump that injects a tracer solution into a stream during a stream tracer test

Collecting invertebrate samples to assess the community composition of a mining-impacted stream, Upper Animas River Watershed, Colo.

USGS equipment trailer -- bringing tracer tests to Rocky Mountain streams

One of the "obstacles" facing USGS scientists studying the impact of abandoned mine sites on Rocky Mountain watersheds, Mineral Creek, Colo.

Spacing sampling points along a stream prior to a tracer test on Mineral Creek, Colo.

Filling a holding tank with a tracer solution prior to the start of a stream tracer study, Upper Animas River Watershed, Colo.

Abandoned mine site in the Boulder River Watershed, Mont. -- one of the watersheds in the USGS Abandoned Mine Lands Initiative

Crystal Mine at Uncle Sam Gulch, Boulder River Watershed, Mont.

Comet Mine Mill, Mont., with glory hole where valley-fill tailings were placed

Mill tailings deposited on the flood plain of Basin Creek in the Boulder River watershed, Montana, 1998. USGS geologist and USDA Forest Service engineer are discussing scientific findings of the USGS Abandoned Mine Lands Initiative and implications for remediation being planned by the USDA Forest Service for the Buckeye mine and mill tailings