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 INL. Weekly precipitation samples are collected from the Experimental Field Station (EFS) on the INL. Surface and/or drinking water are sampled twice each year at 19 locations around the INL. This occurs during the second and fourth quarters.

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 monthly composites from Idaho Falls and CFA, and weekly from the EFS. Precipitation samples are analyzed for tritium. Storm events in the third quarter of 2006 produced sufficient precipitation to yield six samples – one from Idaho Falls, three from CFA, and two weekly samples from the EFS.

Tritium was measured above the 3s value in two of the samples collected during the third quarter 2006 at CFA and EFS. 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. The EPA’s RadNet 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 2006). Tritium detected in third quarter ESER samples were within this range, with a maximum of 219 ± 31.4 pCi/L (8.1 ± 1.2 Bq/L) at Idaho Falls. Data for all third quarter 2006 precipitation samples collected by the ESER Program are listed in Table C-6 (Appendix C).