The U.S. Department of Energy says mercury discharges at the Y-12 nuclear weapons plant have declined in recent years, due — at least in part — to a Recovery Act-funded project in 2011 that cleaned out and repaired the plant’s storm sewer system.
However, there are multiple factors associated with the mercury levels in East Fork Poplar Creek, the recipient of Y-12’s discharges for decades, and so it’s not clear if the mercury reduction has been fully documented or if that downward trend will continue.
The situation is complicated.
According to DOE estimates, the Oak Ridge plant currently discharges about 3.7 grams of mercury per day into the East Fork, which originates inside Y-12 and flows through much of Oak Ridge’s west end before joining Poplar Creek and ultimately the Clinch River and downstream reservoirs.
The concentration of mercury in the creek, based on samples taken last year at Station 17, the point where the East Fork leaves government property, is about 840 parts per trillion in water.
That far exceeds the long-term goal of 51 parts per trillion, which would bring DOE into compliance with Clean Water Act standards. But DOE spokesman Ben Williams said the mercury concentration is below the levels measured in 2009, before the start of the WEMA (West End Mercury Area) cleanup project at Y-12, and a sign of progress.
As part of the WEMA project, workers removed about 54 pounds of elemental mercury from Y-12’s stormwater collection system and sealed cracks and holes in the concrete that had allowed mercury contamination to infiltrate the system and reach the creek at Outfall 200 — the point where the underground pipelines converge.
DOE has acknowledged that mercury discharges to the creek actually increased during and immediately following the project because work on the storm sewer stirred up old pockets of mercury and flushed the material into the creek.
“Since then we have seen a steady decline,” Williams said in response to questions.
The Tennessee Department of Environment and Conservation, which closely monitors the Oak Ridge mercury situation in conjunction with the U.S. Environmental Protection Agency, has a somewhat different perspective.
While TDEC said it is encouraged “and fully supports” DOE’s efforts to reach compliance with the mercury standard, the state raised questions about the meaning of some results in recent years.
“In its evaluation of the DOE’s 2015 Remediation Effectiveness Report, TDEC observed a reported reduction in mercury flux in 2014,” spokeswoman Kelly Brockman said via email. But the state said the reported data for 2011, 2012 and 2013 show almost the same levels of mercury as reported in 2009.
Also, Brockman noted that rainfall was down by about 20 percent in 2014, suggesting that the WEMA project may not have been the reason — or at least not the sole reason — for reduced mercury levels.
“TDEC agrees with DOE that there are several other factors having varying impacts on mercury flux rates at Station 17,” Brockman said.
Among those factors was the decision to stop augmenting the flow of water in the creek’s headwaters. After weapons production activities declined at Y-12 in the post-Cold War era, the amount of cooling water discharges at the plant dropped as well. In order to maintain a minimum flow and to sustain aquatic life in the East Fork, DOE began pumping millions of gallons of raw water from Melton Hill Lake on a daily basis.
Beginning in May 2014, however, DOE stopped adding water to the East Fork to meet a state directive to help reduce the amount of mercury flushed downstream.
Mercury contamination in Oak Ridge date backs to the 1950s, when Y-12 used enormous quantities of the toxic metal to process lithium for use in hydrogen bombs. But the public didn’t learn about the mercury problem until the 1980s, when the government declassified documents that revealed the Cold War project and gave some indication of the environmental problems.
According to DOE, about 24 million pounds of mercury was brought to Y-12 for the lithium work.
Spills were not uncommon. Tons of mercury seeped into the soil at the plant or leaked into the East Fork.
DOE estimates that 700,000 pounds was lost to the environment, including tons of airborne releases and mercury that still resides in the cracks and crevasses of buildings. The government still cannot account for about 1.3 million pounds of the mercury stockpile.
The WEMA cleanup project illustrates the potential for future difficulties, when deactivation and demolition of old, contaminated buildings takes place at Y-12. There will be continuing risks of stirring up the mercury mess and dispersing it during cleanup operations.
A $146 million treatment plant at Outfall 200 is supposed to help manage the mercury pollution before it reaches the creek.
Besides the day-to-day treatment of discharges, the facility will have the capability to store large amounts of runoff water during heavy storms — which historically have flushed mercury into the creek.
The proposed treatment facility is supposed to come online around 2022, depending on funding.
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