The ESER program samples precipitation, surface water, and drinking water. Monthly composite precipitation samples are collected from Idaho Falls and the Central Facilities Area (CFA) on the INEEL. Weekly precipitation samples are collected from the Experimental Field Station (EFS) on the INEEL. Surface and/or drinking water are sampled twice each year at 19 locations around the INEEL. This occurs during the second and fourth quarters and is therefore not reported here. A summary of approximate minimum detectable concentrations (MDCs) for radiological analyses and DOE Derived Concentration Guide (DCG) (DOE 1993) values is provided in Appendix B.
Precipitation samples are gathered when sufficient precipitation occurs to allow for the collection of the minimum sample volume of approximately 20 mL. Samples are taken of a monthly composite from Idaho Falls and CFA, and weekly from the EFS. Precipitation samples are analyzed for tritium. Storm events in the first quarter of 2004 produced enough precipitation for a total of 12 samples – three from Idaho Falls, three from CFA, and six from the EFS.
Data for all first quarter 2004 precipitation samples collected by the ESER Program are listed in Table C-6 (Appendix C). Tritium was measured above the sample’s 3s value in one sample collected from CFA on February 2, 2004. The tritium concentration was 191.0 ± 55.7 pCi/L (7.1 ± 2.1 Bq/L). While there is no regulatory limit for tritium in precipitation, the DOE DCG and maximum contaminant level set by EPA for tritium in drinking water can be used as a measure of comparison. The concentration measured at CFA is many times lower than the DCG value (2 x 106 pCi/L) and the Safe Drinking Water Act limit (20,000 pCi/L) for tritium in drinking water.
Low levels of tritium exist in the environment at all times as a
result of cosmic ray reactions with water molecules in the upper atmosphere.
Tritium measured in first quarter ESER samples were within the range of values
measured elsewhere. The EPA’s ERAMS program collects precipitation samples from
across the United States. From 1978 to 2001 tritium measured in those samples
ranged from -2.00 to 7.38 x 106 pCi/L (-7.4 to 2.7 x 104
Bq/L) (EPA 2002).