Updated information on Good Samaritan policy that will limit liability for Good Samaritans improving water quality at draining abandoned mines is now on the EPA web site (cut/paste below): http://water.epa.gov/action/goodsamaritan/index.cfm

Good Samaritan

The Good Samaritan Initiative is an Agency-wide initiative to accelerate restoration of watersheds and fisheries threatened by abandoned hard rock mine runoff by encouraging voluntary cleanups by parties that do not own the property and are not responsible for the property's environmental conditions. The Good Samaritan administrative CERCLA tools were issued on June 6, 2007. The tools are a model comfort letter and a model settlement agreement (an administrative order on consent or "AOC"). The Agency also issued a memorandum to EPA Regions in 2007, describing the purpose and intended use of the tools.

On December 12, 2012, EPA issued a memorandum to its regional offices that encourages cleanup activities at hard rock abandoned mine sites. The memorandum is intended to reduce the perceived Clean Water Act legal vulnerability faced by "Good Samaritans" who want to clean up their communities. There are hundreds of thousands of abandoned mine sites across the nation and many pose serious health, safety, and environmental hazards. Many community organizations have been looking at opportunities to clean up these sites and EPA's memorandum clarifies that these "Good Samaritans," or non-liable parties, who volunteer to clean up these abandoned sites are generally not responsible for obtaining a permit under the Clean Water Act (CWA) both during and following a successful cleanup.