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The former, residential private wells sampled by the Rhode Island Department of Health (RIDH) in June 1993 showed that 10 of the private wells near the spill area contained low levels of chloroform, 1,1,1-trichloroethane (1,1,1-TCA), 1,1-dichloroethane (1,1-DCA), and 1,1-dichloroethene (1,1-DCE). Chloroform (at a concentration of 1 part per billion (ppb) was detected in only one private well. 1,1-DCA and 1,1,1-TCA were detected in six of the wells with concentrations ranging from 1.4 to 12 ppb and from 1 to 20 ppb, respectively. The levels of 1,1-DCE found in two of the wells ranged from 1 to 1.7 ppb. These levels are below levels which would be expected to produce any covert effects. Although trichloroethene (TCE) and tetrachloroethene (PCE) were detected in some of the wells between 1979 and 1984 (1, 3), the 1993 sampling did not detect TCE or PCE in any of the private wells. Although some households are still using these wells, a staff of the RIDH confirmed that the wells have not been tested since 1993.

In 1994, the Office of Drinking Water Quality of the RIDH sampled a private well directly across from the site. Testing showed that the water contained 12 ppb of TCE. As a result, the house was switched to the public water supply system (2). This level is below levels which would be expected to cause adverse health effects. There is no indication that the private well is being used for potable purposes.

However, EPA used monitoring wells they installed in the area to collect samples in the tenth- and eleventh-quarter of phase II in 1995 and 1996 (4, 5). Contaminants detected in on-site groundwater during the tenth-quarter (September/October 1995) included TCE (below detectable limits to 100,000 ppb),1,2-dichloroethene (DCE) at below detectable limits to 23,000 ppb, and vinyl chloride (at detectable limits to 740 ppb). Further evaluation of the sample results indicated that the levels of TCE fluctuated with depth between two sampling occasions.

The most, frequently, occurring organic compounds detected during the eleventh sampling event onsite were TCE, 1,2-DCE, and vinyl chloride. TCE was detected from below detectable limits to 62,000 ppb, 1,2-DCE from below detectable limits to 19,150 ppb, and vinyl chloride from below detectable limits to 230 ppb. The Concentrations of all organic compounds sampled tended to fluctuate by increasing during the tenth sampling in September/October 1995 (4), and by decreasing in the October 1996 sampling event (5).

These trends indicate that the contaminants 1,2-DCE, vinyl chloride, and trace amounts of dieldrin are present in the contaminant plume under the TCE spill area and spreading (4, 5). In the September/October sampling event (4), trace amounts of 1,3-dichlorobenzene, 1,2-dichlorobenzene, 1,4-dichlorobenzene, 1,2,4-trichlorobenzene, and dieldrin were also detected in groundwater monitoring wells onsite.

Should these levels of TCE impact drinking water wells in the future, adverse health effects including congenital heart disease, eye and ear abnormalities, and leukemias might occur in children born to potentially exposed mothers. Similarly, people who might be exposed to this level of vinyl chloride might experience less serious liver problems including hepatoma.

The primary organic compound detected in monitoring wells offsite was TCE at low levels during the 1995 and 1996 sampling events. Because historical data have indicated the absence of TCE in off-site monitoring wells, it is likely that the TCE detected may be attributable to a variety of reasons including sample contamination from either sampling equipment, laboratory equipment, or field error. Other explanations could be that the edge of the plume is reaching the off-site wells, or the depth at which samples are drawn is above or below the plume thus lowering the concentration.

In order to comply with the Rhode Island Order of Approval, analysis of Inorganic constituents were also conducted in both on-site and off-site wells during the tenth, and eleventh sampling quarters in 1995 and 1996 (4, 5). The metals detected in monitoring wells with concentrations greater than primary and secondary standards were aluminum, iron, lead, manganese, chromium, cooper and zinc. When both the dissolved and the total fraction of the inorganics were analyzed, total inorganics were higher than dissolved concentrations(with the exception of few landfill areas). The suspended particulates may be contributing to most of the elevated inorganics detected, which can be filtered out prior to treatment of volatile organic compounds (VOCs).

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