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OF-00-16 Naturally Degraded Surface Waters Associated with Hydrothermally Altered Terrane in Colorado

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This study (now superseded by publication B-54) describes the water quality of several areas in Colorado that show the effects of naturally degraded surface water. It focuses on areas where hydrothermally altered host rocks are the primary cause of degradation. Often, areas with naturally degraded water overlap mining districts, where mining-related degradation also occurs. This information will be useful for State and Federal agencies and private owners for developing realistic reclamation plans for active and abandoned mines in areas where natural degradation is a contributor to poor water quality. Digital PDF download. OF-00-16D

From the author’s notes:

During the field season of 1999, Colorado Geological Survey (CGS) personnel conducted a reconnaissance-level investigation of naturally degraded surface waters associated with hydrothermal alteration in Colorado. Selected streams and springs were sampled in southwestern, west-central, central, and north-central Colorado. Locations were in the San Juan Mountains, La Plata Mountains, Rico Mountains, Grizzly Peak caldera, Ruby Range, Montezuma stock, Red Amphitheater, Twelvemile Creek, Rabbit Ears Range, and Never Summer Range. Data from this study may be useful when regulatory agencies set stream standards. This information could also be useful for determining remediation goals for past and/or future mining operations.

Many of these sites were initially identified by water testing done in conjunction with an abandoned mine inventory conducted by the CGS for the USFS from 1991 through 1998. Personnel from the U.S. Geological Survey, the Colorado Division of Minerals and Geology, and Colorado State University were also important sources of preliminary information. A publication on iron occurrences in Colorado describes numerous bog-iron deposits, many which are associated with naturally degraded water.

A study of this scope cannot catalog and characterize every naturally degraded, metal-rich stream in Colorado. It may serve as a guide to identify areas of Colorado that are susceptible to these phenomena and provide general information regarding water chemistry at these occurrences. Many of the areas described in this report should be the foci of detailed watershed characterization studies to better understand the natural and anthropogenic processes involved in the surface-water chemistry.