BIOLOGICAL ASSESSMENT OF THE EFFECTIVENESS OF MINE SITE REMEDIATION

Water quality and aquatic life of the Animas River and its headwater tributaries in SW Colorado has been significantly impacted by hard rock mine related activities. Use Classifications set by the Colorado Department of Public Health and Environment mandate that the Animas and its tributaries meet certain criteria that include the presence of viable populations of macroinvertebrates and trout. Currently, mine site remediation is taking place to clean up mine site discharge to the degree, and with the goal, that the tributaries and the Animas River meet these Aquatic Life Use Classifications.

In 1996 and 1997 macroinvertebrate, water chemistry and physical habitat data were collected to: 1) identify the relationship between macroinvertebrates, water chemistry and physical habitat, and 2) to establish pre-remediation conditions to assess the effectiveness of mine site remediation. Specific questions included: when and where to sample, how often to sample, what community metrics to use and whether or not to identify and use indicator species to assess the effectiveness of the remediation.

In fall 1996, spring 1997, and fall 1997, 68 sites were sampled from the headwaters of the Animas River to the confluence with the San Juan River in New Mexico. Data was collected from the mainstem, both upstream and downstream of tributaries, as well as within the mouth of tributaries.

Analysis of the data indicated that the populations varied considerably from tributary to tributary and from segment to segment, often within a distance of less than a kilometer and were related to variances in physical and water chemistry data. Thus, post-remediation sampling must be specific to tributaries and segments and driven by the degree of clean up within each tributary and within each segment. Community metrics were useful in obtaining an overall view of the data, but will not be specific enough to be useful in evaluating the effectiveness of the remediation. Indicator species are also too limiting to be of use. Instead, each species within each segment and tributary must be followed closely and related to the changes in water chemistry and habitat data to accurately assess the effectiveness of the remediation.