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The Oconomowoc Electroplating Co., Inc. site is located in the unincorporated town of Ashippun, a rural area about 35 miles west of Milwaukee. It operated from 1957 to the early 1980s as an industrial facility that used metals, chemicals and organic compounds in its production process. During that time, the company discharged untreated wastewater into nearby wetlands and Davy Creek. Two unlined lagoons on the property contained electroplating sludge. These lagoons leaked and sometimes overflowed. Contaminants made their way into the ground water beneath and downstream of the site.

The contaminants, called volatile organic compounds, or VOCs, include trichloroethylene (TCE).  They are used in electroplating and degreasing operations.  Vinyl chloride is produced when TCE degrades in the natural environment. The company used TCE while it was in operation.

After the plant closed, EPA listed OECI as a Superfund site. Investigations into how much environmental damage had been done began in the mid-1980s. EPA made a decision on how to clean up the vacated buildings, soil, lagoons, Davy Creek and wetlands in 1990. From 1992 to 1996, EPA:

The cleanup has been reviewed three times (1997, 2002, and 2007) to ensure that people and the environment are still being protected. Although the pump and treat process eliminated much of the ground water contamination, its efficiency was diminishing over time as highly mobile contamination was removed. After doing a special study called an "optimization study" in 2004, EPA decided to shut down the pump and treat system. Since then, natural processes have been cleaning up the remainder of the contamination.

Private wells near the site have been sampled regularly since 2005. Results show very low levels of TCE in the wells, but are not a health risk.

In 2011, EPA revised its plan to clean up on-site ground water (underground supply of fresh water) that was contaminated by toxic metals and VOCs.

Under the new plan, called the Record of Decision Amendment (PDF) (83pp, 6.73 MB) May 2011, natural processes will treat ground water contaminants. Also, residual source areas would be looked at to determine the extent of contamination. This information would then be used to select either excavation or in-place chemical treatment to enhance source-area biological activity and remove VOCs.

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