Water that is sampled by the ESER program includes surface water, drinking water and precipitation. Surface and/or drinking water are sampled twice each year during the Second and Fourth Quarters at 19 locations around the INEEL (see schedule). Monthly composite precipitation samples are collected from Idaho Falls and the CFA on the INEEL. Weekly precipitation samples are collected from the EFS on the INEEL.
When adequate precipitation occurred, samples were taken on a monthly interval from Idaho Falls and CFA, and on a weekly interval from EFS. A minimum precipitation sample volume of approximately 20 mL is needed for a single sample. Precipitation samples are analyzed for tritium. For the first quarter of 2001, there was enough precipitation for a total of ten samples – three from Idaho Falls, three from CFA, and four from EFS. Of the three samples collected from Idaho Falls, two, (from January and March) had results greater than their associated 2s values. The February sample was below the MDC and the March sample was above the MDC (Appendix B, Table B-1). Of the four samples collected from EFS, all were above 2s, however, only one (week of January 17) was above the MDC. Of the three samples collected from CFA, the January sample was above 2s, but was below the MDC.
blanks (submitted as part of normal QA/QC procedures) for precipitation
sampling also had results greater than their associated 2s uncertainties
and MDCs. Therefore, there
is a high probability that one or more of these results were false
positives (see the Confidence
section). While there
is not a DCG for precipitation, the SDWA sets a limit for tritium in
drinking water of 2 x 104 pCi/L (Appendix
B). The level of
tritium detected in the samples that were above their associated 2s and
MDC values was between 110 and 160 times lower than the level set by the
SDWA, and was within the range of background
tritium that exists throughout the world.
While tritium was detected (above 2s and above the MDC) in precipitation from Idaho Falls and EFS, and an INEEL source cannot be discounted for contributing to this, the measured level was within the range of background tritium that exists throughout the world. Low levels of tritium exist in the environment at all times. The major natural source of tritium is cosmic ray reactions in the upper atmosphere. From 1978 to 2001 the EPA, as part of its ERAMS, measured tritium from –2.00 x 102 to 7.38 x 106 pCi/L in precipitation samples across the United States (EPA, 2002). Data for all precipitation samples for the first quarter 2001 are listed in Table C-6 (Appendix C).