Uranium contamination in the Great Miami Aquifer—at the Fernald Preserve, Ohio, Site—is being removed from the groundwater through a pump-and-treatment operation, which until this year, involved the operation of 23 extraction wells. Figure 1 shows the footprint of the uranium plume and the 23 extraction wells. Concurrence and support from the U.S. Environmental Protection Agency (EPA), Ohio EPA, and site stakeholders allowed the implementation of operational changes that are predicted to increase the effectiveness of the ongoing operation and shorten cleanup times for a portion of the aquifer.

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Figure 1. Waste Storage Area (WSA) phase II design well
locations and 2011 maximum uranium plume footprint.

Groundwater remediation is proceeding successfully, as reported each year in the Fernald Preserve Site Environmental Report (SER). At the end of 2013, 11,784 pounds of uranium had been removed from the aquifer. The Record of Decision for Operable Unit 5 states that the U.S. Department of Energy (DOE) has committed to continuing pumping operations until it can be demonstrated, with reasonable certainty, that the final remediation level of 30 micrograms of uranium per liter of water (μg/L) has been attained at all affected areas of the aquifer. The final remediation level is based on EPA National Primary Drinking Water Regulations.

The progress of groundwater remediation is reported each year in the SER. Operation metrics indicate that, although still working, the remedy is becoming slightly less effective each year. Data trend indicates that the effectiveness will continue to reduce as the remedy progresses. This type of decline is common for pump-and-treatment operations. However, rather than simply continuing to operate and accepting the current trend as the norm for the technology being used, the DOE Office of Legacy Management is choosing to re-examine the operation in order to find an innovative approach for improving the remedy effectiveness, shortening its time span, and reducing costs.

In addition to decreasing effectiveness, sampling indicated that a portion of the aquifer had higher uranium concentrations than originally characterized for the area in 2005, when the final cleanup design was modeled. In order to obtain a more accurate model-predicted cleanup time, the groundwater model needed to be updated with new uranium plume data.

Modeling results (using updated uranium plume data) predicted longer cleanup times if no operational changes were made. The area groundwater model was used to simulate several operational changes, including adding new extraction wells, varying the pumping rates of existing extraction wells, or both. New modeling results indicated that the best approach required no additional extraction wells, only operational changes to the existing wells.

Operational changes implemented so far in 2014 involve shutting down three extraction wells that no longer benefit the ongoing cleanup, and reallocating the pumping budget from the three shutdown wells to existing wells in the southern South Field and South Plume. Figure 2 shows the three extraction wells that were shut down (EW-28a, EW-31, and EW-32). The groundwater model predicts that with these operational changes the southern South Field and South Plume will clean up faster than previously predicted (2 years faster for the plume area south of Willey Road, and 8 years faster for the plume area north of Willey Road).

To achieve accelerated cleanup of the plume areas, the target pumping rate for the groundwater remediation system is being increased by 300 gallons per minute (gpm) for 8 years to provide an operational boost in the target area (see Figure 2). Once remediation goals are achieved, pumping can be reduced for the two remaining plume areas on DOE property, the northern South Field and Waste Storage areas (see Figure 1). Figure 2 shows that during years 9 through 16 the pumping rate will be reduced by 1,700 gallons per minute (gpm), and during years 17 through 21 the pumping rate will be reduced by 3,675 gpm. Operational costs are slightly higher the first 8 years due to increased pumping, but the upfront costs will be offset later by predicted savings due to decreased pumping, resulting in an overall predicted savings of approximately $6.0 million (see Figure 3).

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Figure 2. System pumping rates by year.

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Figure 3. Cumulative estimated costs.