is a good example of a ditch that we have to build on top of a valley field. >> reporter: rocky hackworthwed me the trenches and retention ponds designed to capture runoff, and protect the surrounding environment. >> that way, you don't have anything that leaving the property. downstream, there are no consequences. we've had samples taken out for eight years and we've never had a water issue. >> reporter: the coal industry says it tests water continuously. chris hamilton is the senior vice president of the west virginia coal association. >> it's not something that's done haphazardously. there's a very, very high premium placed on that, and it's a very important aspect, just like personal and individual mine health and safety. >> reporter: but the data tells a different story. we joined emily bernhardt's colleague, eric moore, as he did some fieldwork near the largest surface mine in central appalachia. active for more than 40 years, the hobet mine has transformed about 10,000 acres of natural mountain peaks into manmade mesas. the duke team presides over 14 different monitoring sites, in