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The Animas River Watershed, San Juan County, Colorado By Paul von Guerard, Stanley E. Church, Douglas B. Yager, and John M. Besser Chapter B of Integrated Investigations of Environmental Effects of Historical Mining in the Animas River Watershed, San Juan County, Colorado Edited by Stanley E. Church, Paul von Guerard, and Susan E. Finger Professional Paper 1651 U.S. Department of the Interior U.S. Geological Survey Contents Introduction...................................................................................................................................................19 Acknowledgments .......................................................................................................................................20 Description of the Study Area ...................................................................................................................21 Hydrologic Setting ..............................................................................................................................21 Biologic Setting ...................................................................................................................................25 Geologic Setting ..................................................................................................................................26 Remediation Activities .......................................................................................................................29 Overview of This Volume ............................................................................................................................30 References Cited..........................................................................................................................................37 Figures 1. Index map showing the Boulder and Animas River watersheds ........................................20 2. Shaded relief map and location map of Animas River watershed study area .................22 3. Streamflow hydrograph for years 1995–2000 .........................................................................24 4. Map showing generalized geology of the Colorado part of the Animas River watershed ....................................................................................................................................27 5. Generalized geologic map of Silverton caldera, Animas River watershed study area and vicinity ...............................................................................................................28 Chapter B The Animas River Watershed, San Juan County, Colorado By Paul von Guerard, Stanley E. Church, Douglas B. Yager, and John M. Besser Introduction • Transfer technologies developed within the AML Initiative into practical methods at the field scale and demonstrate their applicability to solve this national Thousands of inactive hard-rock mines have left a legacy environmental problem in a timely manner within the of acid drainage and toxic metals across mountain watersheds framework of the watershed approach in the western United States. More than 40 percent of the watersheds in or west of the Rocky Mountains have headwater • Develop working relationships with the private sector, streams in which the effects of historical hard-rock mining are local citizens, and State and Federal land-management thought to represent a potential threat to human and ecosys- and regulatory agencies, and tem health. In many areas, unmined mineral deposits, waste rock, and mill tailings in abandoned mine lands (AML) may • Establish a scientific basis for consensus and an increase metal concentrations and lower pH, thereby affect- example for future investigations of watersheds ing the surrounding watershed and ecosystem. Streams near affected by inactive historical mines. abandoned inactive mines can be so acidic or metal laden that The combined interagency effort has been conducted fish and aquatic insects cannot survive and some bird species in two pilot watersheds, the Animas River watershed study are negatively affected by the uptake of metals through the area in Colorado (fig. 1) and the Boulder River water- food chain. Although estimates of the number of AML sites shed study area in Montana (Nimick and others, 2004). vary, observers agree that the scope of this problem is huge, Comprehensive scientific investigations conducted in both particularly in the western United States where public lands watersheds clearly indicate that remediation of Federal lands contain thousands of inactive mines. affected by inactive mines will require substantial investment Numerous AML sites are located on or adjacent to of resources. public lands or affect aquatic or wildlife habitat on Federal Land-management and regulatory agencies face two fun- land. In 1995, personnel from a U.S. Department of the damental questions when they approach a region or watershed Interior and U.S. Department of Agriculture interagency task affected by inactive or abandoned mines. First, with potentially force, including the Bureau of Land Management (BLM), hundreds of contaminated AML sites dispersed throughout National Park Service (NPS), U.S. Department of Agriculture a watershed, how should resources for prioritizing, charac- (USDA) Forest Service, and U.S. Geological Survey (USGS) terizing, and restoring the watershed be invested to achieve developed a coordinated strategy for the cleanup of environ- cost-effective and efficient cleanup? Second, how can realistic mental contamination from AML associated with Federal remediation targets be identified, considering lands. As part of the interagency effort, the USGS imple- mented an Abandoned Mine Lands Initiative to develop • The potential for adverse effects from unmined miner- a strategy for gathering and communicating the scientific alized deposits adjacent to existing inactive or aban- information needed to formulate effective and cost-efficient doned mines (including any effects that may have been remediation of abandoned mines on Federal land. Objectives present before premining activity and that still may of the AML Initiative included persist from unmined deposits) • Characterize watersheds and individual sites • The possible impact of incomplete cleanup of specific inactive historical mine sites • Understand the effect and extent of natural sources • Other factors—some possibly as yet unidentified— • Communicate these results to stakeholders, land that may limit sustainable development of desired managers, and the general public ecosystems. 20 Environmental Effects of Historical Mining, Animas River Watershed, Colorado • Gives high priority to actions likely to most signifi- cantly improve water quality and ecosystem health WA MT • Enables assessment of the cumulative effect of multiple Boulder River and (or) nonpoint sources of contamination watershed OR • Encourages collaboration among Federal, State, and local levels of government and stakeholders ID • Provides information that will assist the siting of mine- WY waste disposal areas • Accelerates remediation and reduces total cost com- NV pared to remediating on a site-by-site basis CO UT Animas River • Enables consideration of revenue generation from CA watershed in Colorado selected sites to supplement overall watershed reme- diation costs. This report provides detailed review of field and labora- AZ tory work conducted in the Animas River watershed during NM 1996–2000. The objectives of this work were the following: • Estimate premining geochemical baseline (background) conditions • Define current geochemical baseline conditions Animas River watershed • Characterize processes affecting contaminant dispersal study area Silverton and effects on ecosystem health SAN JUAN • Develop remediation goals on the basis of scientific study of watershed conditions • Transfer useful data and information to users in a LA PLATA timely and effective manner. Expertise in water quality, hydrology, geology, geochem- Durango istry, geophysics, biology, mapping, and database manage- ment was applied during these investigations. Investigations Ignacio were coordinated with the Animas River Stakeholders Group, 0 5 10 15 20 25 MILES Colorado Division of Wildlife, Colorado Department of Public Health and Environment, Colorado Division of Mines and Figure 1. Western United States showing Boulder and Animas Geology, Colorado Geological Survey, U.S. Environmental River watersheds. Animas River watershed study area is shown Protection Agency, USDA Forest Service, and U.S. Bureau of in inset map. Land Management, all of which are coordinating the design and implementation of remediation activities within the watershed. To answer these questions, the Abandoned Mine Lands Initiative adopted a watershed approach, rather than a site- by-site approach, to characterize and remediate AML sites Acknowledgments (Buxton and others, 1997). This approach is based on the premise that acid mine drainage affecting watersheds in a State Our work would not have been possible without the assis- or region should be prioritized on the basis of its effect on the tance of individuals in various State and Federal agencies. We biological resources of the watershed so that the resources thank personnel in the following agencies: spent on remediation will have the greatest benefit on affected Colorado Division of Wildlife and Parks, particularly streams. Within these watersheds, contaminated sites that have Barbara Horn and Mike Japhet for their local the greatest impact on water quality and ecosystem

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