Mercury cleanup efforts intensify

Posted: February 11, 2013 - 3:31pm | Y-12 Report | Volume 9, Issue 2 | 2013

Millions of pounds of mercury were required to support Y‑12's post–World War II mission of separating lithium isotopes. Cleaning up the toxic heavy metal poses many challenges, but what Y‑12 is learning could help conquer mercury pollution worldwide.

There's a reason you won't find mercury in many thermometers these days. Mercury is a heavy metal that occurs in several chemical forms, all of which can produce toxic effects in high enough doses.

Mercury was used in the column exchange process, which Y‑12 employed to produce lithium-6 from 1953 to 1962. Through process spills, system leaks and surface runoff, some 700,000 pounds of mercury have been lost to the environment through the years. Past efforts, including the Central Mercury Treatment System and the Big Spring Water Treatment System, have helped reduce mercury levels in nearby East Fork Poplar Creek, which surfaces on Y‑12 property. And the site has recently ramped up its mercury characterization and remediation efforts.

“Y‑12's biggest challenge in mercury cleanup is protecting workers, especially given the unique magnitude of the potential contamination,” said Diane McDaniel of Y‑12's Environmental Management Program. “Complicating factors include the metal's being entrained in building structures and subsurface features as well as understanding the chemical reactions and mercury compounds present on-site. Each variant poses potentially unique risks and cleanup considerations.”

Thanks to an influx of cash from the American Recovery and Reinvestment Act of 2009, or ARRA, Y‑12 has accomplished some of its most significant remediation efforts in decades, including scrap metal removal, soil characterization and soil remediation in the Old Salvage Yard and removal of mercury-contaminated sediments from the West End Mercury Area storm sewer system. The storm sewer remediation project removed almost 4,000 cubic feet of mercury-contaminated solids from the subsurface.

"ARRA really kick-started us, but that money is running out now,” McDaniel said. “How do we keep that momentum going?"

Her group has outlined a detailed path forward with near-, short- and long-term actions. Ultimately, the plan is to remove legacy materials from contaminated facilities, isolate the structures from the rest of the plant before they are dismantled and demolished, and then remediate the underlying soil.

For fiscal 2013, roughly $26 million saved during other ARRA projects has been scoped for further remediation projects. Those projects include continued removal of mercury from key locations in the site storm drains, isolation of buildings' former mercury migration pathways and a preliminary conceptual design of a water treatment facility. “We're getting more attention for these issues, so I'm optimistic we'll get more funding,” McDaniel said.

She also noted mercury's evolving recognition as an international pollutant — and Y‑12's ability to help the global community. “We're also looking into some innovative technologies and evaluating some alternative treatment methods for mercury-contaminated waste that are more efficient and will give us more bang for our buck,” she said. “This isn't just about Y‑12; mercury is recognized internationally as a toxic contaminant. With our cleanup and remediation experience, there's a real opportunity for us to share our work and findings.”

Still, the immediate goal remains limiting the mercury concentrations in Y‑12's surface water and remediating the local environment. “The mercury concentration levels in East Fork Poplar Creek have been declining over the past several years but are still well above state water quality standards,” McDaniel noted. “But we're improving. And with an issue like this, any progress is good progress.”