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Public Health Assessment
Ciba-Geigy Corporation
(Dover Township) Toms River, New Jersey
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Remedial History
A chronology of selected events related to the investigation and remediation of the CGC site is given in Table 1. Since the CGC site was added by the USEPA to the NPL in 1983, many studies have been conducted by Ciba-Geigy, USEPA, and their contractors to characterize the environmental consequences of activities at the site. Efforts have been focused on characterizing the nature and extent of on-site and off-site
groundwater contamination (called Operable Unit I by USEPA) associated with the CGC- site (Environ, 1996; NUS, 1988a) and on characterization of the on-site source areas of contamination (called Operable Unit 2) (CDM, 1993a).
Groundwater
In January 1985, Ciba-Geigy installed a purge-well system to intercept contaminated groundwater migrating toward the Cardinal Drive/Oak Ridge Parkway residential area. The multiple-well system was reported to pump 0.5 million gallons per day from the Upper Sand Aquifer (NUS, 1988a).
Based on the Remedial Investigation and Feasibility Study (RI/FS) for Operable Unit I (NUS, 1988a; NUS, 1988b), the USEPA issued a Record of Decision (ROD) in 1989 which proposed to extract and treat up to approximately 4 million gallons per day of contaminated groundwater from the Upper Cohansey, Primary Cohansey and Lower Cohansey elements of the Upper Sand Aquifer under the CGC site (IJSEPA,
1989). The extracted water would be treated to achieve LJSFPA and New Jersey Surface Water Quality Standards for metals, total dissolved solids, and VOCS. Under the plan, metals would be removed by precipitation, dissolved solids would be removed by a reverse osmosis process, and VOCs would be removed by aeration. Identified (but unregulated) VOCs would be treated by aeration to achieve either 5 or 50 µg/l, depending on
the chemical's USEPA Weight of Evidence classification for carcinogenicity. The treated water was to be discharged directly (by pipe) to the Toms River. In addition, the ROD also stated that all irrigation wells in the Cardinal Drive/Oak Ridge Parkway residential area should be sealed.
However, in 1993, after requests by interested parties for reconsideration of groundwater discharge options, USEPA issued an Explanation of Significant Differences (ESD) which altered the original proposed ROD by providing for on-site recharge of treated water to the Upper Sand Aquifer, rather than discharge to the Toms River (USEPA, 1993). The ESD also required that groundwater be monitored in the area east of
Toms River to ensure that recharged groundwater or groundwater contaminants would not be drawn into nearby community water supply wells. Monitoring of groundwater along the northern boundary of the CGC site was also required. Table 2 shows the individual pollutants which would be monitored, their health-based ATSDR Comparison Values (CVs) and drinking water Maximum Contaminant Levels (MCLs), and the cleanup compliance standards which were specified in the ESD.
Design of the revised groundwater extraction and treatment system was begun in 1993. Initially, 28 extraction wells were planned; after treatment, groundwater would be recharged to three areas on the CGC plant property (Environ, 1992). The final Groundwater Extraction and Recharge System, which became fully operational in March 1996, incorporates extraction (using a total of 43 wells), treatment (aeration and activated charcoal filtration),
and recharge of up to 2,7 million gallons per day. To reduce the possibility of affecting groundwater flow to community water supply wells located east of Toms River, all treated groundwater has been directed to the northeast recharge area, or NERA (Figure 4).
On-Site Source Areas
A Draft Feasibility Study (FS) for remediation of on-site source areas, initiated in 1995, was published in l999 (CIBA,1999b). The purpose of the FS is to provide an evaluation of remedial alternatives that will enable USEPA to select a remedy for each of the potential source areas that will be protective of human health and the environment, and that will facilitate the remedial goal of groundwater restoration.
Seven alternatives for potential remedial actions have been proposed for consideration. The alternatives range from no action to excavation and removal of all contaminated materials. Other options include natural attenuation with monitoring, containment, in/ex situ thermal treatment, in/ex situ bioremediation, and a combination of the various remedial methods.
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