The 1,050-acre DOE site at Fernald, Ohio lies over the Great Miami Aquifer, one of the largest sources of drinking water in the nation. For over 35 years until 1989, Fernald plants processed uranium metal for U.S. defense programs. Only about 136 acres of the site were actually involved in the production process. Over the years, uranium contaminated a small portion of the aquifer. Reducing the level of uranium in the groundwater to the health-protective concentration limit proposed by the U.S. Environmental Protection Agency (20 parts per billion) is a primary goal of the Fernald Environmental Management Project, managed since 1992 by Fluor Daniel Fernald. The record of decision for Fernald’s Operable Unit 5 calls for restoring the aquifer by 2023 using "pump-and-treat" technology. Sixteen wells have been installed at the leading edge of the plume both on and off site, and during November 1998 these wells extracted a total of more than 140 million gallons of contaminated groundwater from the aquifer. Since beginning in 1993, pumping has removed more than 3.5 billion gallons, and the groundwater uranium concentration in the area of the wells has already been reduced from more than 300 to less than 200 parts per billion. Several treatment facilities remove uranium from groundwater and remediation wastewater, as well as from controlled surface run-off from the more highly contaminated areas at Fernald. The Advanced Wastewater Treatment (AAWT) Facility began operating in 1995, with a design capacity of 1,100 gallons per minute (gpm). A combination of chemical precipitation and ion exchange reduces uranium concentration in the treated water to less than 20 ppb. More than 600 pounds of uranium has been removed from groundwater pumped from the aquifer. Increasing the flow In keeping with DOE’s nationwide effort to sharply accelerate site remediation and closure, an effort is now under way to use a new strategy that could complete the aquifer remediation by 2006. By cutting 17 years off the schedule, this new approach has the potential to help cut aquifer remediation costs by as much as $50–100 million, according to Rob Janke, Soils and Water Program Manager for DOE-Fernald. The key to this acceleration is groundwater reinjection, an integral part of commercial solution mining, or in situ leaching, for over 20 years. Pumping some of the previously removed, treated groundwater back into the aquifer yields a number of benefits:
It seems simple, but long-term reinjection was unproven at Fernald, so, with approval from regulators and stakeholders and support from OST’s Subsurface Contaminants Focus Area, a one-year field-scale demonstration was begun in September 1998. One of the challenges to the demonstration team was to minimize maintenance costs that result when screens in the reinjection wells become plugged, as happens when the chemistry of the reinjected water is not properly adjusted. Data from preliminary testing in 1995–96 provided the basis for tuning the current system. Treated water is being reinjected through five strategically placed wells at the combined rate of 1,000 gpm. During November 1998, that amounted to 43 million gallons. The AWWT was recently expanded to provide additional treatment capacity of 1,800 gpm, most of which will be reinjected into the aquifer. Decisions about employing groundwater reinjection technology for the remainder of the project and adding reinjection capacity won’t be made until this demonstration has revealed its schedule benefits, dependability, and cost-effectiveness, but performance so far is very encouraging. More information about this and other Fernald cleanup projects is available on FEMP’s Web site at www.fernald.gov. For further information on the reinjection demonstration, contact Rob Janke, DOE-Fernald Soils and Water Program Manager, (513) 648-3124, rob_janke@fernald.gov, or John Kappa, DOE-Fernald Water Project Manager, (513) 648-3149, john_kappa@fernald.gov. |
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A solution from solution
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