ASSESSMENT OF NONPOINT-SOURCE POLLUTION FROM INACTIVE MINES USING A WATERSHED-BASED APPROACH

A watershed-based approach for screening-level assessment of nonpoint source pollution from inactive and abandoned metal mines was developed and illustrated. The methodology was designed to use limited stream d ischarge and chemical data from synoptic surveys to derive key informa tion required for targeting impaired waterbodies and critical source a reas for detailed investigation and remediation. The approach was form ulated based on the required attributes of an assessment methodology, information goals for targeting, attributes of data that are typical o f basins with inactive mines, and data analysis methods that were usef ul for the case study. The methodology is presented as steps in a fram ework including evaluation of existing data/information and identifica tion of data gaps; definition of assessment information goals for targ eting and monitoring design; data collection, management, and analysis ; and information reporting and use for targeting. information generat ed includes the type and extent of and critical conditions for water-q uality impairment, concentrations in and loadings to streams, differen ces between concentrations in and loadings to streams, and risks of ex ceeding target concentrations and loadings. Data from the Cement Creek Basin, located in the San Juan Mountains of southwestern Colorado, US A, were used to help develop and illustrate application of the methodo logy. The required information was derived for Cement Creek and used f or preliminary targeting of locations for detailed investigation and r emediation. Application of the approach to Cement Creek was successful in terms of cost-effective generation of information and use for targ eting.