BRATTLEBORO -- Despite concerns that testing of a drinking water well at Vermont Yankee nuclear power plant in Vernon could produce "misleading results that may lead to public confusion," Entergy has agreed to resume sampling of the well.
In a letter dated July 11, Christopher Wamser, Yankee's site vice president, wrote, "We continue to be concerned that grab sampling the (Construction Office Building) well will not add meaningful new information regarding the nature and extent of tritium in the groundwater or understanding of groundwater movement under the site."
Yankee has a number of groundwater monitoring wells it has been testing since it announced in January 2010 that tritiated water was leaking into the ground under the plant.
The source of the leak was determined to be in an underground pipe tunnel connected to the plants advanced off-gas system.
In May of 2010, another leak was discovered in the AOG drain line.
Repairs were quickly made to both the leaks following identification of the sources of contamination.
During the leak discovery process and the clean up of the leak, Entergy tested the various groundwater monitoring wells to determine contamination levels, to track the plume's progression and follow up on remediation efforts.
Because the groundwater monitoring wells were relatively shallow, Entergy also tested the COB drinking water well, which had been drilled to a depth of 364 feet, for two
Very low levels of tritium were detected in the COB well in October 2010 at 312 feet, but not at 364 feet.
Since Entergy stopped taking samples of the well, the state has been insisting in a series of letters that it continue the process.
"We continue to believe that obtaining a grab sample is appropriate for this well, and would not cause any undue risk to the bedrock aquifer, particularly if only a few gallons are removed as is the case in grab sampling," stated a letter dated March 27, 2011. "We have checked with both the EPA's Office of Groundwater and Drinking Water and National Air and Radiation Environmental Laboratory and both agree that taking a grab sample from a well for tritium is an appropriate sampling technique ...."
Justin Johnson, deputy commissioner at Vermont Department of Environmental Conservation, said it's taken a long time for Entergy to agree to resume the sampling.
"We're happy they've come around and actually doing it," he said. "It's taken too long. I would like to think they would be as interested in the outcome of the test as we are."
Entergy stopped the testing out of a concern that it would actually pull contaminated water down to deeper levels.
"Because of the relatively low capacity of the bedrock to transmit water," wrote Wamser in the July 11 letter, "such sampling can induce vertical migration of groundwater ... and produce results that do not reflect groundwater migration under normal conditions."
In the July 11 letter, Wamser wrote, "testing could produce inconclusive and potentially misleading results that may lead to public confusion about the nature and extent of tritium contamination of groundwater at the site."
Nonetheless, after meeting with a representative from the EPA, Entergy developed a sampling plan it believes "should satisfy the state that the deep bedrock aquifer remains safe."
Other on-site and off-site drinking water wells have been tested in the past two years with negative results.
Since the leak was discovered, groundwater monitoring wells confirmed that the plume was moving from the point of the leak toward the Connecticut River.
Entergy extracted hundreds of thousands of gallons of contaminated water from the ground during remediation.
Testing of river water determined that while tritiated water was seeping into the river, it was at levels just above the minimum level of detection of 500 picocuries per liter.
The EPA's limit for tritium in drinking water is 20,000 picocuries.
At the height of the leak response, at least one groundwater monitoring well had samples of more than 2 million picocuries.
Bob Audette can be reached at firstname.lastname@example.org, or at 802-254-2311, ext. 160.