Water Sampling

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

Precipitation Sampling

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 third quarter of 2002 produced enough precipitation for a total of 14 samples (11 samples and three splits) – three from CFA, three and two splits from Idaho Falls, and five and a split from the EFS.

Tritium was measured above the samples' 2s value in ten samples and two split samples: all the CFA and EFS samples, and three samples from Idaho Falls. 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 screening values. The highest tritium detected concentration,
290 ± 58.5 pCi/L (10.7 ± 2.2 Bq/L), was from the sample collected from CFA on July 30, 2002. This value 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 third 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). Data for all third quarter 2002 precipitation samples collected by the ESER Program are listed in Table C-6 (Appendix C).