Drinking Water

Fourteen drinking water samples and one duplicate were collected from selected taps throughout southeast Idaho. Samples were analyzed for gross alpha, gross beta, and tritium (³H). Only the water samples from Fort Hall and Moreland exceeded their 2s and MDC values (Table 5).

TABLE 5. Drinking water results > 2s and > MDC.

	Sample Results		Values for Comparison
	Result (pCi/L) ± 2s	MDC (pCi/L)	SDWA (pCi/L)	DCG (pCi/L)
Location	Tritium
Fort Hall	129.3 ± 74.0	104.8	2 x 10⁴	8 x 10⁴
Moreland	111.8 ± 72.0	104.8	2 x 10⁴	8 x 10⁴
	Gross Beta
Aberdeen	5.00 ± 2.06	2.33	50	100
Taber	4.10 ± 1.92	2.33	50	100
Fort Hall	6.94 ± 2.07	2.33	50	100
Minidoka	2.72 ± 1.75	2.33	50	100
Roberts	4.54 ± 1.89	2.33	50	100
Shoshone	3.62 ± 1.80	2.33	50	100
Atomic City	3.75 ± 1.70	2.33	50	100
Monteview	11.02 ± 2.58	2.33	50	100
Mud Lake	4.65 ± 1.59	2.33	50	100
Moreland	5.94 ± 2.36	2.33	50	100
	Gross Alpha
Minidoka	1.32 ± 0.96	0.57	15	30
Arco	0.94 ± 0.87	0.57	15	30
Atomic City	0.75± 0.74	0.57	15	30
Monteview	1.99 ± 1.41	0.57	15	30

All drinking water samples had gross beta results above 2s, and all but four (those from Carey, Arco, Howe and Idaho Falls) were greater than their associated MDCs.

Of the samples analyzed for gross alpha, four, those from Minidoka, Arco, Atomic City, and Monteview, were greater than 2s and their associated MDCs.

The SDWA limits tritium in drinking water to 2 x 10⁴ pCi/L. The level of tritium detected in the samples from Fort Hall and Moreland that were above 2s and the MDC were 155 to 179 times lower than the SDWA limit. The measured levels were also 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 ‑9.00 x 10¹to 1.00 x 10³ pCi/L in drinking water samples across the United States (EPA, 2002).

The SDWA limits gross beta in drinking water to 50 pCi/L. The level of gross beta detected in the samples that were above 2s and the MDC were between 4 to 18 times lower than the SDWA limit.

The SDWA also limits gross alpha in drinking water to 15 pCi/L. The level of gross alpha detected in the samples that were above 2s and the MDC were between 7 to 20 times lower than the SDWA limit.

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. All drinking water sample results may be found in Appendix C, Table C-7.

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