Dover Township Municipal Landfill & Silverton Private Well Contamination Investigation<BR>Toms River, New Jersey

Dover Township Municipal Landfill & Silverton Private Well Contamination Investigation
Toms River, New Jersey

Discussion

This Discussion will review the history of remedial activities conducted in relation to the DTML site and to private wells in the Silverton section of Dover Township, and the findings of investigations of environmental contamination. Based on these findings, an analysis of exposure pathways will be presented. At this time, available information is limited to the potential for exposure to contaminated groundwater. Therefore, this Public Health Assessment will only discuss this pathway. The Discussion will conclude with an assessment of the public health implications of completed exposure pathways.

Remedial History

DTML/Silverton Road Groundwater Investigation

In 1987, the NJDEP began to collect groundwater quality data from 27 private potable wells along Silverton Road, an area immediately adjacent to the DTML (see Figure 1). This area was originally classified in 1974 as potentially threatened by groundwater contamination (Ghassemi, 1976). Wells in this area utilize the Cohansey Aquifer, and average 70 to 90 feet in depth. One-third of the wells sampled by NJDEP exhibited contamination with volatile organic chemicals (VOCS) similar to those compounds detected in DTML monitoring wells (NJDEP, 1990). As a result of the impact of the DTML upon private wells in the area of the site, the NJDTP determined there was sufficient evidence to warrant the capping of the impacted residential wells and extension of community water service to the affected area under the New Jersey Spill Fund Act (N.J.S.A. 58:10-23.11 et seq.) (Mack, 1990).

A Preliminary Assessment of the DTML has been conducted by a contractor for Dover Township with the oversight of the NJDEP (Raviv, 1997a). A geophysical survey identified possible locations of UCC drums within the landfill. A Remedial Investigation is currently underway by the contractor for Dover Township (Raviv, 1997b).

Silverton Private Well Contamination Investigation

The Silverton Private Well Contamination Investigation site is located in the Silverton section of Dover Township (see Figures I and 5). The NJDEP investigated a groundwater contamination plume affecting private wells located on Mount Lane, Larch Drive, and Becchtree Drive. According to the Ocean County Health Department (OCHD) and Silverton residents, wells in this area utilize the Cohansey Aquifer and tend to be relatively shallow, averaging 60 to 80 feet in depth. In June 198 1, the OCHD began to receive complaints from residents in Silverton regarding chemical tastes and odors in private well water. The source of the contamination was thought by the NJDEP and the OCHD to have originated from a leaking underground storage tank. The NJDEP inspected all gasoline stations in the vicinity, but an inventory showed that none were missing product, and no potential sources of the contamination were identified at the time (NJDEP, 1981).

In February 1982, the NJDEP issued an Administrative Order directing Dover Township to expedite the connection of affected residences to the community water supply, and to cap contaminated private wells (Schiffinan, 1982). In April 1982, 78 private wells were capped and the community water supply was extended to the residences. The New Jersey Spill Compensation Fund was used to cover the costs of installing the water lines to affected residences.

Throughout the period from 1982 to 1989, the NJDEP installed and sampled monitoring wells in the Silverton area (Diaz, 1985). These monitoring wells continued to indicate the presence of benzene, xylene, 1,2-dichloroethane, and chloroform, but a source of the groundwater contamination was never established by the NJDEP.

Environmental Contamination

DTML/Silverton Road Groundwater Investigation, 1988

Table 1 (see Appendix for tables) summarizes the contaminants detected by the NJDEP in the DTML monitoring wells between 1987 and 1989 (NJDEP, 1990). Volatile organic contaminants included benzene, chlorobenzene, dichlorobenzenes, methylene chloride, and naphthalene. Lead and arsenic were also found in the monitoring wells.

In 1990, the NJDEP issued the "Silverton Road Private Wells Ground-Water Impact Area Report," which presented analytical data for twenty-seven private wells sampled by the NJDEP from 1987 to 1989 (NJDEP, 1990). These wells were described by the NJDEP as being affected by off-site migration of contaminants emanating from the DTML. The contaminated wells were located along Silverton Road. Nine of the wells exhibited contamination with volatile organic compounds and/or lead. Table 2 summarizes the contaminant levels found during this investigation. Six of the wells contained one or more of the following contaminants at levels exceeding health comparison values: benzene, tetrachloroethylene (also known as perchloroethylene, or PCE), vinyl chloride and lead. (See the appendix for a definition and description of the use of comparison values.)

The "Pathways Analysis" and "Public Health Implications" sections of this Public Health Assessment evaluate the public health significance of the private well water data generated during the DTMU Silverton Road Groundwater Investigation.

Silverton Private Well Contamination Investigation, 1982

In January and February 1982, the Ocean County Health Department (OCHD) and the NJDEP sampled private potable wells in the Silverton section of Dover Township. The majority of the wells were located on Mount Lane, Larch Drive, and Beechtree Drive (Figure 5). Twenty wells (designated as "well A through "well T" in Table 3) exhibited contamination with VOCS. Table 3 summarizes the data generated during this investigation (Diaz, 1985). Sixteen of these 20 wells contained at least one of the following contaminants at levels exceeding comparison values: methylene chloride, 1,2-dichloroethane, chloroform, carbon tetrachloride, 1,2-dichloropropane, trichloroethylene (TCE), 1,1,2,2-tetrachloroedme, benzene and chlorobenzene.

The "Pathways Analysis" and "Public Health Implications" sections of this Public Health Assessment evaluate the public health significance of the data generated during the Silverton Private Well Contamination

Investigation.

NJDHSS/ATSDR Groundwater Investigation, 1997

As part of the activities conducted for this Public Health Assessment, and in support of other activities denoted in the PHRP for the Dover Township Childhood Cancer Investigation, the NJDHSS and the ATSDR initiated an exposure investigation in 1996. One part of the exposure investigation was an effort to supplement existing data on groundwater quality by sampling private wells in the Township in 1997. A summary of the exposure investigation will be provided separately, but information from the private well testing that is relevant to the DTML site and the Silverton section is also presented here.

A total of fifty-four private wells were sampled by the NJDHSS from February through May 1997. Of these, twenty were located in areas pertinent to the RF and DTML health assessment study areas (Figure 4). Analyses were performed utilizing standard methods 524.2, 525.2 and 625 for organic chemicals, and other standard methods appropriate for heavy metals, gross alpha and beta activity (900.0 903.0), general chemistry, and dissolved oxygen. Of the twenty wells in this area, four contained chloroform in the range: of 0.4 to 4.0 mg/l, below the ATSDR comparison value (cancer risk evaluation guide: 6 mg/l) and the drinking water maximum contaminant level (MCL) of 100 mg/l for trihalomethanes, a group of chemicals to which chloroform belongs. Chloroform is not considered to be a DTML site-r-elated contaminant.

Eighteen of these 20 wells contained lead (range: 1.5 to 27.4 mg/l) (NJDHSS, 1996-1999, Volumes 68 to 81). The presence of lead is most likely a result of corrosion of household plumbing by acidic groundwater, and is not related to the DTML site. Samples from several private wells exceeded the MCL for gross alpha activity (15 pCi/L). Gross alpha activity was determined to be due to radium species (224, 226, 228) in groundwater. The presence of radium in the Cohansey aquifer is a phenomenon not associated with the DTML site, and is common to many areas of southern New Jersey. The public health significance of lead and radium in these private wells will be discussed in the separate summary of the exposure investigation.

Pathways Analysis

To determine whether residents of Dover Township were or are exposed to contaminants migrating from the DTML site, the ATSDR and the NJDHSS evaluate the environmental and human components that lead to exposure. An exposure pathway consists of five elements: (1) a source of contamination; (2) transport through an environmental medium; (3) a point of human exposure; (4) a route of human exposure; and (5) a receptor population.

The ATSDR and the NJDHSS classify exposure pathways into three groups: (1) completed pathways, that is, those in which it is likely that some persons in the receptor population were exposed, are being exposed, or will be exposed; (2) potential pathways, that is, those in which exposure might have occur-red, may be occurring, or may yet occur; and (3) eliminated pathways, that is, those which can be eliminated from further analysis because one of the five elements is missing and will never be present, or in which no contaminants of concern can be identified. Completed or potential pathways may be interrupted by remedial actions.

DTML/Silverton Road Groundwater Investigation

The ATSDR and the NJDHSS have determined that a completed human exposure pathway to DTML- related groundwater contaminants existed in the past through the domestic use of private wells on Silverton Road near the landfill. Exposure may have occurred through ingestion, inhalation or dermal contact, depending on water use patterns and volatility of contaminants. Contaminants in the pathway at levels above comparison values include: benzene, PCE, vinyl chloride and lead.

The presence of contaminants was documented between 1987 and 1989. Based upon an assumed discharge from the DTML occurring in 1971, and compound-specific migration rates calculated by the NJDEP, wells may have been contaminated with benzene as early as 1973, or with PCE by 1977 (Montgomery, 1990). Lead was found in samples of all six of the on-site monitoring wells; it also occurred in several private potable wells in conjunction with other site-related contaminants. This information suggests that the lead in the private wells was site-related. The exposure to VOCs and lead through this pathway was interrupted in 1991 when New Jersey Spill Fund claims financed the voluntary connection of the community water supply to affected residences in the area adjacent to the landfill.

The total number of persons associated with this past exposure pathway based upon the number of households is estimated to be approximately 23 (nine residences times 2.5 persons per residence) (ATSDR, 1992a). The NJDHSS/ATSDR exposure investigation did not indicate the presence of VOC or semi-volatile organic chemical contaminants in private wells sampled in the area.

The following table summarizes the completed human exposure pathway for the DTML/Silverton Road Groundwater Investigation area:

Completed Human Exposure Pathway
Associated with the Dover Township Municipal Landfill

Pathway Name	Source	Environ- mental Media	Point of Exposure	Route of Exposure	Exposed Population	Contaminants (Time Documented)
DTML/ Silverton Road Private Wells	DTML	Ground water	Residences with private wells	Ingestion, dermal contact, inhalation	Residents (Estimated 23 persons)	VOC's and Lead (1987)

The nature and extent of the DTML groundwater contamination plume is currently under investigation. Furthermore, the status of the DTML as a continuing source of groundwater contamination has not been determined. Therefore, there is a potential future exposure pathway associated with the use of private potable wells down gradient of the DTML site.

Silverton Private Well Contamination Investigation

The ATSDR and the NJDHSS have determined that a completed human exposure pathway to groundwater contaminants existed in the past through the domestic use of private wells in the Silverton section of Dover Township. Exposure may have occurred through ingestion, inhalation or dermal contact, depending on water use patterns and volatility of contaminants. Contaminants in the pathway at levels above comparison values include: methylene chloride, 1,2-dichloroethane, chloroform, carbon tetrachloride, 1,2-dichloropropane, TCE, 1, 1,2,2-tetrachloroethane, benzene and chlorobenzene.

Contamination of private wells was first documented in June 1981 in response to taste and odor complaints, but may have existed for an unknown amount of time before then, as contaminants increased to a noticeable level. The pathway was interrupted at the time that community water supplies were extended to affected residences beginning in April 1982.

The NJDHSS and the ATSDR could not address the community's concern that groundwater contamination in the Silverton section was associated with the DTML, because of uncertainty of the following factors: the source or sources of the contaminants; times of contamination; and the direction and velocity of groundwater and contaminant flow. However, if the DTML was a source, contaminant migration rates estimated by the NJDEP suggest that the most mobile compounds (benzene, 1.6 feet/day) might have taken as much as approximately 13 years to travel the approximately 8,000 feet between the DTML and the Silverton section private wells.

The total number of persons associated with this past exposure pathway based upon the number of households is estimated to be approximately 50 (20 residences times 2.5 persons per residence) (ATSDR, 1992). The NJDHSS/ATSDR exposure investigation did not indicate the presence of VOC or SVOC contaminants in private wells sampled in the area.

The following table summarizes the completed human exposure pathway for the Silverton Private Well Contamination Investigation area:

Completed Human Exposure, Pathway
Associated with the Silverton Private Well Contamination Investigation

Pathway Name	Source	Environ- mental Media	Point of Exposure	Route of Exposure	Exposed Population	Contaminants (Time Documented)
Silverton Private Wells	Unknown	Ground water	Residences with private wells	Ingestion, dermal contact, inhalation	Residents (Estimated 50 persons)	VOC's (1981)

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