Acid mine drainage (AMD) can cause ecological harm throughout the state of Colorado, including in the Upper Animas River watershed near Silverton. In the Upper Animas River watershed, a technique that includes the emplacement of hydraulic bulkheads within draining mines has been used to remediate AMD. Data for major ions and trace metal concentrations, isotopic compositions, and discharge from streams, draining mines, and springs were compiled for a period of approximately 30 years to better understand the processes occurring during the impoundment of water within underground mine workings and to define spatial extent of groundwater connectivity. These datasets were evaluated using statistical and geochemical modeling approaches.