The site is approximately 60 miles southwest of St. Louis, adjacent to the city of Sullivan in Franklin County, along Interstate 44. The legal location of the site is Section 4, Township 40 North, Range 2 West. The total human population within four miles of the site is estimated to be 6,800.
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The site is an uncontrolled plume of trichloroethylene (TCE) initially detected in a municipal drinking water well. The Oak Grove Village well drew water from an aquifer that can best be described as karst limestone and dolomite, which are highly soluble and characterized by features such as caves, springs, and solution conduits. Groundwater flow direction at the site is uncertain due to the karst feature throughout the area; the flow is to the northeast, but it could be to the north or to the east. There are over 100 private wells around Oak Grove Village drawing water from the same contaminated aquifer. Several private wells in the Oak Grove Village vicinity have been found to exceed the Federal Safe Drinking Water Act maximum contaminant levels (MCLs) for TCE. In 1986, the Missouri Department of Natural Resources (MDNR) encountered levels of TCE in the Oak Grove Village city well at 6 parts per billion (ppb). The MCL for TCE is 5 ppb. Following the original detection of TCE, MDNR continued to sample the Oak Grove Village well on a quarterly basis from June 1986 through October 1990, resulting in levels ranging from 6 to 25 ppb.
In December 1990, MDNR issued Oak Grove Village a Notice of Violation due to the TCE levels in the city well exceeding the MCL. In July 1991, Oak Grove Village closed the well and began purchasing water from the city of Sullivan. In September 1992, Oak Grove Village reopened the well and disconnected from the Sullivan water supply. MDNR reinstated sampling of the well. TCE was again detected above the MCL, and continued to be detected above the MCL through February 1994 when the well was closed again and capped.
MDNR conducted a Preliminary Assessment (PA) and a Site Inspection (SI) at the site. The PA was completed in June 1987, and the SI was completed in October 1988. Several potential sources of TCE were identified during the MDNR investigations and during environmental inspections conducted for private companies. These potential sources include the Sullivan Landfill, TRW Automotive Products Inc., a former Ramsey Division facility (TRW), the Sohn property, and the Blanton property. TCE was detected in soil and/or groundwater samples collected at three of these sites; however, existing information was not adequate to sufficiently document attribution to any of these areas as the source of the TCE detected in the Oak Grove Village well.
The Environmental Protection Agency (EPA) completed an Expanded Site Inspection (ESI) in September 1994 to identify possible source(s) of TCE contamination; to establish quantities for the source(s); and to provide hazard ranking system (HRS) quality sampling, and analytical data. The analytical data from the ESI field sampling did not result in data sufficient to meet the HRS project objective of documenting a source of the TCE contamination and an associated hazardous waste quantity.
TRW, one of the potential sources identified in the PA/SI, entered into a Resource Conservation and Recovery Act (RCRA) 3008(h) corrective action order with the EPA on March 29, 1993. TRW implemented an EPA/MDNR-approved RCRA groundwater monitoring plan that included hydrogeologic assessment and groundwater sampling of private, city, and TRW wells. Reports from this work documented the presence of the karst setting, and the releases of TCE and its breakdown products into soil and the groundwater. EPA and MDNR have approved a RCRA Facility Investigation Report that defines the vertical and horizontal extent of releases from the former TRW facility. The work by TRW to date has not shown a direct hydrologic or chemical relationship to the Oak Grove Village well. At present, the EPA and the MDNR, under RCRA authority, are developing a final decision with regard to public comments received during the public comment period in 2000.
A Remedial Investigation/Feasibility Study (RI/FS) has been initiated under a cooperative agreement between the EPA and the MDNR Superfund programs. Since TCE is present in the Oak Grove Village well, the RI will center on this well and work its way out through the surrounding vicinity. Investigative techniques such as sampling public and private water wells, surface water sampling, spring sinkhole sampling, installation of monitoring wells, and possibly dye traces will be completed both within and outside Oak Grove Village to further define the TCE groundwater plume in three dimensions.
The MDNR (in a letter dated August 4, 2000) asked the EPA to provide an alternate water source to two homes with levels of TCE exceeding the MCL. Groundwater sampling indicated TCE contamination in private wells at the homes at 12.8 and 16.4 ppb. In August 2006, whole house water filtration systems were installed at these two residences.
In January and February 2017 the two properties had their original treatment systems replaced with a more current model that is easier to maintain. During this same time, one additional property was found to have TCE exceeding the MCL and a whole house water filtration system was installed.