1) Go to the EPAs National Primary Drinking Water Regulations website. Which contaminants are likely to enter into drinking water as a result of mining activities, based on what you learned about mining-related externalities in the "Mining Impacts" reading?
https://www.epa.gov/ground-water-and-drinking-water/table-regulated-drinking-water-contaminants
2) For each contaminant on your list created in 2), determine if a "strict" safety standard approach has been used to determine allowable levels of the contaminant, or if the EPA has, to some extent, considered the costs of water treatment in setting the standard.
3) Pick one contaminant for which costs/benefits or regulation were considered in setting the maximum contaminant limits. Use the EPA and any additional resources you need, discuss the costs and benefits of regulating the contaminant to the Maximum Contaminant Limit (MCL) that were considered when these limits were set, and describe the process by which the final MCL was determined.