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 Site.  Weekly precipitation samples are collected from the Experimental Field Station (EFS) on the INL Site.  Surface and/or drinking water are sampled twice each year at 19 locations around the INL Site.  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 fourth quarter of 2006 produced sufficient precipitation to yield 12 samples –three from CFA and Idaho Falls and six weekly samples from the EFS.

Tritium was measured above the 3s value in three of the 12 samples collected during the fourth quarter of 2006.  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 1980 to 2005, tritium measured in samples from Region 10 (which includes Idaho) ranged from -200 to 7500 pCi/L (EPA 2006).  Tritium measured in all second quarter ESER samples were within this range and were consistent with historical measurements at the INL Site, with a maximum of 124.0 ± 30.3 pCi/L at CFA.  Data for all fourth quarter 2006 precipitation samples collected by the ESER Program are listed in Table C-6 (Appendix C).

Drinking Water

Fourteen drinking water samples and one duplicate were collected from selected taps throughout southeast Idaho (Figure 11).  Samples were analyzed for gross alpha, gross beta, and tritium (³H).

Figure 11.                Drinking and surface water sampling locations.
 

Two of the samples exceeded the 3s value for gross alpha. It is not unusual to detect this constituent in water of the Snake River Plain, related to natural production from the basalts that make up the aquifer.  The maximum detectable result, a sample from Atomic City, had a gross alpha concentration of 1.81 ± 0.38 pCi/L.  This value is below the EPA and DOE limits for gross alpha in drinking water of 15 pCi/L and 30 pCi/L, respectively

Of the fifteen drinking water samples (including the duplicate) collected, all samples but one exceeded their 3s 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 was from Fort Hall and was lower than the SDWA screening value. Levels of gross beta observed in drinking water are not unusual given the basaltic terrain (USGS 2003).  All values are similar to those recorded in previous years, and are well below the levels outlined for drinking water protection (Appendix B-1).  All drinking water sample results may be found in Appendix C, Table C‑7.

Tritium was detected in two of the samples collected.  Detectable tritium concentrations were 92 ± 24 pCi/L at Mud Lake and 93 ± 29 pCi/L at Shoshone.  Both values are well below the EPA limit of 20,000 pCi/L and the DOE DCG of 2.0 x 10⁶ pCi/L. Tritium values were within historical data collected by the ESER and within EPA measurements made through the RadNet program in Region 10 (Alaska, Idaho, Oregon, and Washington), which ranged from -87 ± 37 pCi/L to 1402 ± 63 pCi/L in the period 2000-2005.