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In 2004 and 2005, the Pennsylvania Department of Environmental Protection (PADEP) identified the presence of tritium (3H ) in over 90% of the landfill leachate samples from 54 permitted landfills in Pennsylvania. While 3H is produced naturally in the upper atmosphere by cosmic ray interaction with nitrogen (14N) in air, it is also produced artificially during nuclear weapon production/use, as a byproduct in nuclear power production, and for other uses. It is these other uses that are most likely to be disposed of in municipal solid waste landfills, and most notable among these are gaseous tritium light source (GTLS) devices used as emergency ‘EXIT’ signs. Despite regulatory requirements, accidental disposal of GTLS devices in municipal solid waste landfills is not uncommon (PADEP 2005, 2006a). These exit signs typically contain 10-15 curies of tritium but some contain as much as 30 Curies, and they typically have usable life spans of 10-20 years due to the relatively short 12.32 year half life of tritium1.

Tritium is not a treatable constituent in landfill leachate. Consequently, when evaluating the results of the two sampling events, PADEP properly recognized that it was necessary to consider appropriate dilution factors both through publicly owned treatment works and/or from the discharge structures to the nearest downstream drinking water intake. Based on the review of many factors including the concentrations of tritium observed, the location of treated liquid effluent discharge points, leachate discharge rates, dilution factors of receiving streams and distance to downstream water supply intakes PADEP converted the observed leachate tritium concentrations into diluted concentrations assumed to be available for human consumption at the closest drinking water supply downstream from the leachate discharge structure. PADEP performed this dilution analysis for each of the 54 landfills, and after applying the PADEP dilution factors, the resulting concentrations of 3H were found to be well below not only the United States Environmental Protection Agency (USEPA) maximum contaminant level (MCL) of 20,000 pCi/L for 3H for drinking water, but also well below 10% of that MCL. (PADEP 2006b).

In support of this preliminary work, the PADEP in cooperation with the solid waste industry, initiated a sampling study to evaluate fluctuations and trends in tritium levels. This report presents the results of the study and provides comparison to the preliminary studies performed. As part of this study, samples were collected from 54 active landfills over 8 consecutive calendar quarters from the 2nd quarter of 2007 through the 1st quarter of 2009. The leachate 3H concentrations ranged from (-38) to 356,774 pCi/L, with a mean concentration of 38,091pCi/L. Roughly 52% (216 out of 416) of the samples had concentrations >20,000 pCi/L.