Tuesday, Oct. 20, 2009 | 3:01 p.m.
Scientists have found radioactive tritium from nuclear tests in Nevada contaminating groundwater off the Nevada Test Site for the first time.
However, state and federal studies indicated the contaminated groundwater would leave the nuclear site within 50 years.
A groundwater sample taken in a new well drilled on Air Force land contained tritium at about 12,500 picocuries per liter, below the federal Environmental Protection Agency Safe Drinking Water Act limit of 20,000 picocuries per liter. A picocurrie is a measure of radiation in liquid.
The Energy Department predicted in February that groundwater contamination would leave the Test Site boundary near Pahute Mesa, in the northwest corner of the sprawling site about 85 miles northwest of Las Vegas.
The nearest public water source to the new government test well, completed Oct. 12, is 14 miles away.
Tritium occurred naturally in lakes, rivers and public water supplies at between 5 and 25 picocuries per liter before nuclear weapons testing began in 1945 in New Mexico. Tritium is formed in nature from cosmic rays striking hydrogen. It is produced in nuclear explosions as well.
Current plans are to drill six more test wells on and near Pahute Mesa over the next two to three years, said Darwin Morgan, a spokesman for the National Nuclear Security Administration, which operates the Test Site for the Energy Department.
These future wells will be drilled as part of the Energy Department's extensive groundwater monitoring program. They will go down about 3,500 feet at a cost of about $5 million each.
The groundwater monitoring program includes well drilling, sample collection, analysis and evaluation, and computer modeling to better monitor the extent and nature of groundwater contamination at the Test Site, which is larger than the state of Rhode Island.
The first nuclear experiment on western Pahute Mesa occurred in 1966. In total, the government tested 1,021 nuclear devices above and below ground at the Nevada Test Site from 1951 to 1992.