SENECA — More well water samples will be taken near three nuclear power plants Thursday as part of South Carolina Department of Health and Environmental Control work to monitor and protect groundwater.

The tests will help determine whether certain types of radioactive materials might be present in the groundwater, said Thom Berry, a health department spokesman.

Mary Nguyen Bright with the health department’s nuclear response and emergency environmental surveillance section said the retesting is being completed in response to a new nuclear industry effort to monitor and protect groundwater quality in and around all the nation’s nuclear power plants.

Bright said the off-site testing in South Carolina began last summer, and the Nuclear Regulatory Commission already monitors groundwater through wells on site at nuclear power plants.

“The nuclear industry wanted to show here’s the testing, and here are the results,” Bright said. “All nuclear plants are required to build the testing wells themselves. DHEC also wanted to be proactive and check off sites that could indicate if there is an issue.”

Jason Walls, a spokesman for Duke Energy at the Oconee Nuclear Station, said there was no contamination of ground water at the plant and that Duke officials continue to monitor groundwater on a regular basis.

Ten sites initially were tested near Oconee Nuclear Station in February.

“Anytime we have an ‘at, near or above’ reading, we go back,” Bright said.

Bright said two private wells would be rechecked Thursday in Oconee County, one in Fairfield County near the V.C. Summer nuclear plant and 10 in York County near the Catawba nuclear plant.

Bright said the additional testing sites in York County were expected because such elements as uranium, radon and radium occur naturally in the earth, particularly in mountainous areas or higher elevations.

“DHEC has a program to test groundwater, and funds were available to perform these tests,” Bright said. “John Q. Public can have the same type of test done, but it is a little pricey at $200 to $300. A test for bacteria is about $30.”

The health department already has completed testing at the H.B. Robinson nuclear plant in Darlington County. Testing at the Progress Energy-owned plant began in Dec. 2007, and 15 sites were checked. No adverse effect to groundwater or surface was detected, according to health department officials.

Bright said it would be roughly eight to 12 weeks before the results from the latest round of tests were available.

The safe limit in a drinking water well is 20,000 picocuries (pee-co-curies) per liter. A picocurie is one-one thousandth of a curie, a unit to measure radioactivity. After tritium was found in one monitoring well at the Catawba site, tests were conducted at a total of 25 public and private water wells near the site last October.

Tritium is the man-made substance usually first detected in wells because it bonds easily with water, Bright said.

Only one well was found to have a trace of tritium. Bright said that tritium trace measured 248 picocuries or .02 percent of the safe amount allowed.

“The well owner described it as a grain of sand going into the well every 70 years,” Bright said. “That’s pretty accurate.”

Bright also noted that tritium is the same stuff that makes a wristwatch glow or an exit sign shine when the power isn’t working.

“It’s all around us,” Bright said.