Tritium found in drinking-water-supply well

Contact: Kevin Roark, camerahead@lanl.gov, (505) 665-0582 (00-141)

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LOS ALAMOS, N.M., Oct. 24, 2000 -- Hydrologists at the U.S. Department of Energy’s Los Alamos National Laboratory have detected traces of tritium in a well that supplies drinking water to the county of Los Alamos, confirming an earlier reported detection of the radioactive element this year by state regulators.

The tritium was found in concentrations that are 500 times lower than the federal drinking water standard, but are above background concentrations that can be found in groundwater around the Laboratory.

All wells that supply drinking water to Los Alamos meet standards established by the federal Safe Drinking Water Act and by the New Mexico Environment Department. Laboratory hydrologists regularly monitor, and will continue to monitor, wells to ensure that water produced from them meets drinking water standards. In addition, the Laboratory is drilling a number of wells throughout the Los Alamos area to investigate whether any threats to drinking water quality exist, and to ensure the future safety of the water supply.

Tritium is an isotope of hydrogen that is produced naturally in the atmosphere when cosmic rays strike atoms and molecules. Man-made tritium is used for some Laboratory activities. Chemically, tritium’s behavior is identical to hydrogen and it moves easily with water. Tritium is used in self-illuminating exit signs, gun sights, watch dials and other consumer products. The half life of tritium is about 12.5 years.

Hydrologists with the Laboratory’s Water Quality and Hydrology Group took samples from the water-supply well — called Otowi-1, located in lower Pueblo Canyon several miles east-northeast of the Laboratory’s main technical area — in late June as part of the Laboratory’s on-going drinking water monitoring and surveillance program. Although Otowi-1 was constructed in 1990, it did not become operational until 1997. Major water production from the well began last spring.

The Laboratory’s drinking water monitoring and surveillance program looks for the presence of Laboratory-derived chemicals in the aquifer that supplies Los Alamos with drinking water and in other underground water sources.

The Otowi-1 well-water sample was analyzed by an independent laboratory.

The sample showed tritium at a concentration of 38.5 picocuries per liter. Federal drinking water standards say water is safe to drink if it contains tritium in concentrations lower than 20,000 picocuries per liter. Concentrations of tritium in the regional aquifer in other parts of the Laboratory can be found ranging between one and three picocuries per liter; tritium concentrations in Northern New Mexico surface water and rainwater range from 30 to 40 picocuries per liter. A curie is a measure of radioactivity; pico means one-trillionth of a unit.

Hydrologists with the New Mexico Environment Department in January reported that samples taken in June 1999 from the Otowi-1 supply well contained tritium in concentrations of 39.9 picocuries per liter.

"Our data match up pretty well with data obtained earlier by state of New Mexico hydrologists and it verifies their previous finding," said Bob Beers of the Laboratory’s Water Quality and Hydrology Group. "We have detected tritium in the regional aquifer before in Test Well-1 in Lower Pueblo Canyon, but we haven’t previously detected it in these concentrations in a community water-supply well. We will continue to monitor Otowi-1 to determine whether tritium concentrations are increasing or decreasing over time, and we will continue to monitor other drinking-water-supply wells to determine whether any other contaminants are making their way into the aquifer. That is part of the Laboratory’s commitment to helping verify that the water is safe to drink — and it is safe to drink."

In earlier times at the Laboratory, contaminants were discharged into Acid Canyon. Those discharges ceased in the early 1960s. Acid Canyon drains into Pueblo Canyon, so the former Acid Canyon waste treatment plant could be a source of the tritium contamination. Laboratory hydrologists have known since the 1950s that surface water in Pueblo Canyon slowly seeps into deeper underground water bodies over time, although this seeping surface water has little effect on the chemistry of the deeper water. Higher tritium concentrations are regularly found farther upstream in Pueblo Canyon; in shallow water bodies some 100 feet below ground but well above the regional aquifer, tritium concentrations are about 2,200 picocuries per liter of water.

Tritium also has been seen in the deep aquifer in a test well several hundred yards downstream from the Otowi-1 supply well. The concentration of tritium in Test Well-1 was 360 picocuries per liter in 1993. The test well just penetrates the top of the regional aquifer about 600 feet beneath the canyon floor. In contrast, the area within the aquifer from which Otowi-1 draws its water begins at just about 1,000 feet below the canyon floor (and about 400 feet lower than the top of the aquifer and Test Well-1) and continues down an additional 1,460 feet.

Otowi-1 was in the news earlier this year when hydrologists detected trace concentrations of the chemical perchlorate. The non-radioactive chemical also was used in earlier nuclear-weapons-related activities, but was not found in concentrations that could present an increased risk to the safety and health of the public.

Hydrologists at the Laboratory will continue to regularly monitor area drinking-water-supply wells for the presence of perchlorate, tritium and other contaminants.

More news releases from the Environment, Safety and Health (ESH) Division