Staff Reports
WC Monitor
11/6/2015

Some mercury cleanup activities at the Y-12 nuclear weapons plant are seemingly starting to pay off with results in the environment, although much more remains to be done to address the plant’s biggest legacy from the Cold War.

The Department of Energy’s Office of Environmental Management in Oak Ridge said discharges of mercury into the East Fork Poplar Creek have dropped to about 3.7 grams per day, and the mercury concentration in the creek water – measured at Station 17, where the East Fork leaves federal property and flows through much of Oak Ridge’s west end – is at about 840 parts per million.

That, according to DOE spokesman Ben Williams, is below levels in 2009, which was before the DOE sponsored the West End Mercury Act (WEMA) cleanup project in 2011 that removed mercury from the site’s storm sewer system and made significant repairs to the underground maze of concrete pipelines. By sealing the cracks and holes in the system, the project was intended to halt additional in-leakage of mercury from contaminated soils at the plant site and to reduce the off-site discharges via the East Fork – which originates inside the plant.

It is not clear, however, how much the WEMA project – which was funded with American Recovery and Reinvestment Act money – contributed to the reduced mercury levels, and it’s also not clear if more reductions can be anticipated in the near term.

DOE’s environmental staff has acknowledged that the WEMA project actually increased the mercury-in-the-creek statistics for a while, both during and after the project was carried out at Y-12. The cleanup work stirred up and mobilized some of the mercury pollution, which got flushed downstream at higher levels. “Since then we have seen a steady decline,” Williams said.

But it doesn’t appear that the decline in mercury levels has been fully evaluated to determine what results can be attributed to WEMA and how much is due to other factors. Future results might tell the story.

The Tennessee Department of Environment and Conservation indicated that other factors could be more important to the current monitoring stats than the WEMA project.

“In its evaluation of the DOE’s 2015 Remediation Effectiveness Report, TDEC observed a reported reduction in mercury flux in 2014,” TDEC spokeswoman Kelly Brockman said via email, “while the reported data for 2011, 2012, and 2013 shows almost the same levels of mercury as in 2009.”

Brockman added, “Please note that 2014 had about 20 percent less rainfall” – suggesting another reason for the reduced level of mercury in the creek. However, the TDEC spokeswoman said the state is “encouraged” and “fully supports” the federal agency’s efforts to reach the ambient water quality criteria of 51 parts per trillion, as set forth by the Clean Water Act.

Brockman said the state of Tennessee and DOE agree that multiple factors can be impacting the results in mercury rates at Station 17. Rainfall, for instance, can directly affect the mercury concentrations, she said.

As part of the WEMA project, workers removed about 54 pounds of elemental mercury from Y-12’s stormwater collection system, but the bigger contribution might have been keeping more mercury out of the storm system, which has been described in the past as a speedway for the toxin to reach the creek and downstream reservoirs.

Another apparent factor in the recent mercury reduction was the decision to stop augmenting the flow of water in the creek’s headwaters. That stopped in May 2014.

DOE initially started augmenting the flow – with millions of gallons daily from Melton Hill Lake – in the post-Cold War period (around 1996) to help sustain the creek habitat. That was necessary because the reduced work on nuclear weapons also reduced the amount of cooling waters released from Y-12.

The state directed the end of augmentation to help stem the flushing out of mercury from the mercury-laden sections of the Upper East Fork in the middle of the plant.

Mercury contamination at Y-12 is a legacy of the plant’s Cold War work on hydrogen bombs. The Oak Ridge site used millions of pounds of mercury to process lithium for use in the thermonuclear weapons, and spills were not uncommon. Roughly 2 million pounds of mercury were either lost to the environment, seeped into the building structures, or were simply unaccounted for during operations in the 1950s and 1960s.

Future cleanup projects at Y-12 will have to be balanced by the possibility of stirring up more contamination, a problem experienced during the WEMA work.

A new $146 million treatment plant at Outfall 200 is being planned, and is supposed to help further drive down the mercury amounts reaching the creek, which has been posted as a hazard since late 1982. The new treatment facility is supposed to come online around 2022, depending on DOE funding.