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

• Drinking Water

• Surface Water

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 fourth quarter of 2002 produced enough precipitation for a total of eight samples and one split – three and a split from Idaho Falls, two from CFA, and four from the EFS.

Tritium was detected above the 2s value in six samples: one from the CFA, two from Idaho Falls and three from the EFS. 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 concentration of 212.0 ± 58.7 pCi/L (7.9 ± 2.2 Bq/L), was measured in the sample collected from CFA on December 12, 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 fourth 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 fourth quarter 2002 precipitation samples collected by the ESER Program are listed in Table C-6 (Appendix C).

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Drinking Water

Fourteen drinking water samples and two duplicates were collected from selected taps throughout southeast Idaho (Figure 11 below). Samples were analyzed for gross alpha, gross beta, and tritium (³H). A single water sample from Minidoka exceeded its respective 2s and 3s values for gross alpha.

All sixteen water samples collected exceeded their 2s value for gross beta (Table 2). The EPA Safe Drinking Water Act (SDWA) limits gross beta in drinking water based on an annual exposure of 4 mrem/yr. Since data are reported from the laboratory as a concentration (i.e., pCi/L) a screening concentration of 50 pCi/L is used to meet this level (Appendix B-1). The maximum concentration of gross beta detected above the MDC was from Fort Hall and was five times lower than the SDWA screening value.

Six samples (Arco, Carey, Fort Hall, Moreland, Shoshone, and Tabor) exceeded the 2s value for tritium. The SDWA limits tritium in drinking water to 20,000 pCi/L (740.7 Bq/L) (Appendix B-1). The maximum concentration of tritium detected was from Arco of 136.0 ± 113.0 pCi/L (5.0 ± 4.2 Bq/L) was well below the SDWA limit. The measured levels were also within the range of natural tritium that exists in the Snake River Plain Aquifer and 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 -9.00 x 10¹ to 1.00 x 10³ pCi/L in drinking water samples across the United States (EPA, 2002).

Figure 11. Drinking and Surface Water Sampling locations.

Levels of gross alpha and gross beta observed in drinking water are not unusual given the basaltic terrain (USGS 1991). All values are similar to those recorded in previous years, and are well below the levels outlined for drinking water protection (Table B-1). All drinking water sample results may be found in Appendix C, Table C-7.

Table 2.  Drinking water gross beta results greater than (>) 2s and MDC values.

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Surface Water

Five surface water samples and one duplicate sample were collected from locations throughout southeast Idaho and analyzed for tritium, gross alpha, and gross beta. None of the samples were greater than their respective 2s values for gross alpha.

All five samples and the duplicate surface water samples were greater than their associated 2s values for gross beta (Table 3). Even at the reported levels, the gross beta values are between 7 and 27 times lower than the SDWA screening value of 50 pCi/L, and between 16 to 54 times lower than DCG values (Table B-1).

Table 3. Surface water tritium and gross beta results greater than (>) 2s and MDC.

The sample and duplicate from Twin Falls both exceeded the 2s value for tritium. Random tritium detections in the surface water springs are not uncommon. The maximum concentration of 173.0 ± 107.0 pCi/L (6.4 ± 4.0 Bq/L) is well below the EPA and DOE regulatory limits for tritium in drinking water.

The presence of gross alpha and gross beta in surface water (particularly the springs) is typically related to dissolution of naturally occurring radionuclides (i.e., uranium, radium, potassium) by groundwater as it flows through the surrounding basalts (USGS, 1997). Tritium in surface water is a combination of that produced naturally in the upper atmosphere and deposited by rain as well as remnants from worldwide fallout related to nuclear testing. Levels of gross alpha, gross beta, and tritium in all samples are similar to results from recent years. All gross alpha and gross beta results can be found in Appendix C, Table C-7.

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