Range Resources used chemical and low-grade radioactive isotope “tracers” to chart and analyze the reach of hydraulic fracturing done on a gas well in Amwell in 2009. Pittsburgh Post-Gazette, Pennsylvania. Oct 16 2015 http://powersource.post-gazette.com/local/2015/10/16/New-information-surfaces-in-water-well-contamination-complaint/stories/201510160195