The former Aurora high-capacity grain storage facility was located on the northeast corner of 1st Street and East 12th Road intersection in Aurora, Nebraska. In 2011, well sampling data (collected by U.S. Environmental Protection Agency and Nebraska Department of Environmental Quality) from area drinking water wells indicated that CCl4 may have been released to groundwater during the operation of this facility. The contaminated residential drinking water wells associated with the Aurora Groundwater site are located primarily in the southeast area of Aurora, Nebraska, with the identified contamination along East 12th Road southeast of the city.
In 2012 and 2013, the EPA conducted additional water sampling activities that indicated that volatile organic compounds (VOC) were present in seven domestic wells located east of town, outside the city limits, and in one municipal well in northern Aurora. Concentrations of carbon tetrachloride (CCl4) were above federal maximum contaminant levels (MCL) of 5 micrograms per liter (µg/L) in five of the domestic wells. The municipal well contained low levels of the chlorinated solvent tetrachloroethene (PCE).
During the EPA sampling activity a determination was made whether the property owner had installed an in-home water treatment system. Those homes that had a water treatment system had samples collected before (pre-) and after (post-) the in-line treatment system. Sample results indicated that three of the five homes (that had concentrations of CCl4 above 5µg/L in Pre-Treatment water), did not have CCl4 concentrations above 5µg/L in the Post-Treatment water samples. This indicated that the owner-installed water treatment systems were effective in reducing CCl4 concentrations from the water source.
Two of the five previously sampled domestic wells did not have whole-house water treatment systems installed. These samples contained CCl4 at concentrations above the EPA MCL of 5µg/L. The samples collected indicated concentrations of 63µg/L, and 8.4µg/L respectively. In December 2013, a plumbing contractor from Chapman, Nebraska, was contracted by the EPA to install whole house water treatment systems at the two residences. Each whole house water treatment system consisted of an in-line housing containing one sediment filter and an additional in-line housing containing one carbon filter. The purpose of this system is to filter sediment and reduce dissolved volatile organics in groundwater prior to consumption or other domestic use.
In March 2014, confirmation samples collected at the two residences indicated that the whole house filtration system was effective at reducing CCl4 concentrations to levels below the EPA MCL of 5µg/L in the post-treatment water at one home. Samples collected from the second home indicated that CCl4 concentrations in post-treatment water are still above MCL (at 34µg/L). On January 2015, the EPA plumbing contractor installed two additional carbon filtration cartridges at both of the homes. Additional confirmation water sampling from May, 2015, indicated that both homes had CCl4 concentrations below the MCL of 5µg/L .
In May 2017, the EPA provided the home owners of the EPA contractor installed water filtration systems with a certified letter restating the intention and purpose of the whole-house filtration systems, and that the home owner would be responsible for the system maintenance, and future filter cartridge replacements. Upon installation the EPA provided enough filter cartridges to last three years.
