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PUBLIC HEALTH ASSESSMENT
FORMER MACKENZIE CHEMICAL WORKS SITE
CENTRAL ISLIP, SUFFOLK COUNTY, NEW YORK
EPA Facility ID: NYD980753420
September 29, 2004




Summary

The MacKenzie Chemical Works (MCW) site is a light industrial property in the Town of Islip, Suffolk County, New York. Several homes adjoin the site to the south and the east, with the nearest being about 50 feet from the site. Between 1948 and 1987, MCW manufactured a variety of products, chiefly fuel additives and food product intermediates. During this time, chemicals (primarily organic chemicals and solvents) were spilled, leaked, or otherwise discharged onto and into the ground at the site.

Environmental investigations began at this site in 1978, when the Suffolk County Department of Health Services (SCDHS) tested liquids in an on-site leaching pool. Subsequent investigations included on-site groundwater tests in 1985 by the site owner and a Phase II Site Investigation in 1992 by the New York State Department of Environmental Conservation (NYSDEC). SCDHS conducted an off-site groundwater investigation in 1993 and NYSDEC conducted a remedial investigation in 2000. These investigations document the presence of contamination in subsurface drainage structures, soil, groundwater, and soil vapor at the site. The latter two investigations also document a groundwater contaminant plume consisting of 1,2,3-trichloropropane (TCP), a volatile organic compound (VOC) that extends more than ¼ mile from the site.

The primary public health concerns associated with this site are the potential for exposure to chemicals in subsurface drainage structures, groundwater, and soil at the site, particularly if site conditions or use change. These potential exposures relate to TCP in groundwater that may migrate to water supply wells in the future. VOCs in soil gas also may migrate into basements of nearby homes. There are no known exposures to contaminants related to this site currently. Some workers and trespassers may have been exposed to residual contaminants in and around the former MCW buildings in the past.

The Agency for Toxic Substances and Disease Registry (ATSDR) provides guidance for assigning a health hazard category to a site. On the basis of that guidance, the MCW site poses no public health hazard at present because there are no known exposures to site-related contaminants. Significant contamination is present beneath and near the site, however, and future exposure is possible. Consequently, the site poses an indeterminate public health hazard for potential future exposures. Application of the selected remedy will help to limit potential future exposures. Individuals working or trespassing at the site in the past may have been exposed to contaminants. Because data on historic exposures are not available, past exposures, if any, cannot be evaluated.

Future exposure is possible if contaminated groundwater or soil vapor migrate into supply wells or basements. Potential exposures to MCW contaminants via groundwater are checked by periodic monitoring of private water supply wells and routine monitoring of public water supply wells. Soil vapor should be retested to ensure that subsurface vapor migration patterns have not changed since the remedial investigation.

Current land use in the area near the site is commercial, light industrial, and residential. Land use is expected to be similar in the future. Changes in site use or construction activities at the site could result in exposure to subsurface contaminants. In March 2003, the U.S. Environmental Protection Agency (EPA) issued a Record of Decision documenting the selected remedy for the MCW site, which when implemented will significantly reduce or eliminate these potential exposures. Until the remedy is complete, appropriate controls should be used for any excavations that must occur within contaminated areas. At least two on-site structures that may contain residual contaminants from MCW appear to be in danger of collapse. One of the buildings (the former laboratory) will be demolished and removed from the site as part of the EPA's selected remedy. The remaining buildings should be evaluated for structural stability and contamination and handled accordingly.

Community members are concerned about potential health effects from the chemicals used at MCW, chemicals in groundwater beneath schools, the physical hazards posed by decaying on-site buildings, and the contamination in a neighborhood recharge basin. No exposures to contaminants associated with MCW have been found and, therefore, no health effects would be expected. TCP has not been detected in soil vapor off-site in areas with groundwater contamination, thus, indoor air quality in schools or other buildings would not be affected. Contamination from the site would not likely have migrated to the nearby recharge basin. However, potential surface water routes should be re-evaluated and sampled where appropriate.

The New York State Department of Health (NYSDOH) and ATSDR recommend additional investigation and future remedial work at the site to alleviate the continuing threat of exposure. Remedial work should include removal of contaminant sources and treatment of contaminated groundwater.

The public was invited to review the draft of this public health assessment during the public comment period that ran from April 12, 2004, through May 28, 2004. We received no comments from the public during that period.

Purpose and Health Issues

The purpose of this public health assessment (PHA) is to evaluate past, current, and potential future human exposures to site-related contaminants. Moreover, this PHA fulfills the congressional mandate for a public health assessment for each site being proposed to the National Priorities List (NPL). This public health assessment mainly focuses on contaminants detected at and near the site and the potential for exposure to these through soil, groundwater, and soil vapor. There are no known or documented exposures associated with contamination at this site, though some exposures may have occurred in the past. Actions that can be taken to prevent future exposures to site-related contaminants are presented in this document.

Background

Under a cooperative agreement with the Agency for Toxic Substances and Disease Registry (ATSDR), the New York State Department of Health (NYSDOH) evaluated the public health significance of the former MacKenzie Chemical Works site. More specifically, ATSDR and NYSDOH determined whether health effects are possible and recommended actions, listed at the end of this document, to prevent possible health effects. ATSDR is a federal agency within the U.S. Department of Health and Human Services. It is authorized by the Comprehensive Environmental Response, Compensation, and Liability Act of 1980 (CERCLA), as amended by the Superfund Amendments and Reauthorization Act (SARA) of 1986, to conduct public health assessments at hazardous waste sites proposed to the NPL. The MacKenzie Chemical Works site was proposed to the NPL on June 14, 2001, and added to the NPL on September 13, 2001.

Site Description and History

Site Location and Description

The former MacKenzie Chemical Works site is located at 1 Cordello Avenue in Central Islip (Town of Islip), Suffolk County, New York (see Figure 1, Appendix A). The site is approximately 1.4 acres in size in a mixed use (light industrial/commercial/ residential) neighborhood. The site is occupied by Unlimited Paving, Incorporated, which uses the property for the storage and maintenance of trucks and paving equipment. The eastern portion of the site contains piles of construction and demolition (C&D) debris. Three buildings constructed of concrete block and steel are on the site. Two of these-in which little-used equipment are stored-are in disrepair and appear to be near collapse. The third building, also somewhat decrepit, is used as a garage to service trucks and paving equipment. Several houses, a church, and a furniture warehouse border the property (see Figure 2, Appendix A). The Long Island Railroad (LIRR) borders the site to the north. An elementary school, a library, and several stores and restaurants are within ¼ mile of the site.

Site History

MacKenzie Chemical Works (MCW) operated at this site between 1948 and 1987. During this time, MCW manufactured specialty chemicals for shipment off-site. Two of the main items produced at the facility were "Pyrocat," a fuel additive, and dimethyl glycine, a food additive. Miscellaneous research and development activities took place in a laboratory at the site. MCW used and stored bulk quantities of alcohols, ketones, caustic materials, and chlorinated solvents, including tetrachloroethene (also known as perchloroethylene, PCE, or "perc") and 1,2,3-trichloropropane (TCP) at the site. MCW also used significant quantities of 2,4,7-trinitrofluorenone (TNF). Many other chemicals were present at the site and were likely used in small quantities for research and development activities.

Between about 1987 and 1990, the site was used for automobile repair and salvage activities. The present use of the site for storage of paving equipment began in the early 1990s.

History of Investigations at MacKenzie Chemical

A methyl ethyl ketone (MEK) fire at MCW in 1978 focused agency attention on poor housekeeping practices at the site. The Suffolk County Department of Health Services (SCDHS) ordered MCW to clean up the property in 1979. MCW subsequently consolidated waste materials into drums and had some oil-stained soil removed from the site. The SCDHS also began testing liquids that were discharged into subsurface leaching pits at the site. Several leach pit samples were tested between 1978 and 1987 to evaluate the concentrations of organic and inorganic chemicals. In 1982, SCDHS issued a Notice of Violation because of elevated levels of organic chemicals detected in a cesspool (leach pit) at the site.

Staff from NUS Environmental Corporation visited the site on April 14, 1983 on behalf of the U.S. Environmental Protection Agency (EPA) to conduct a preliminary site assessment (NUS Corporation 1983). On the basis of that visit, NUS issued a report recommending that flammable and hazardous materials, debris, and contaminated soil be properly cleaned-up at the site. The report also recommended that the threat to groundwater from chemicals at the site be defined. The owner of MCW completed an on-site groundwater investigation in 1985, which detected some contamination.

The New York State Department of Environmental Conservation (NYSDEC) completed a site investigation in 1992 (NYSDEC 1992). The investigation documented the presence of soil, groundwater, and soil vapor contamination at the site. The investigation report also recommended that empty tanks, debris, and unstable buildings be removed from the site and that the site be secured.

In 1993, SCDHS completed an off-site groundwater investigation downgradient from MCW (SCDHS 1993). The investigation documented the presence of significantly elevated concentrations of TCP in the groundwater plume. The plume was reported to be approximately 1,500-foot long, 300-foot wide, and 140-feet deep, and moving southeasterly from the MCW site.

During 1999 and 2000, the NYSDEC completed a remedial investigation for the MCW site (NYSDEC 2000). The investigation confirmed the presence of contamination at and beneath the former MCW property and defined the extent of groundwater contamination downgradient from the site. It also provided additional information on possible "source areas" of contamination at the site. Source areas are typically localized areas of heavily contaminated soil at spill points or sediments in leaching pits that can act as a continuing source of contamination to groundwater and soil vapor.

EPA collected shallow soil samples in July 2002 to assess the current condition of the surface soils at the site (EPA 2003). Semivolatile organic compounds (SVOCs) were detected in most of the samples at concentrations similar to or somewhat greater than typical levels found in soils.

Current Initiatives

In March 2003, EPA issued a Record of Decision documenting the selected remedy for the MCW site. The remedy includes excavation and off-site disposal of soils contaminated with SVOCs, in-place treatment of soils and groundwater to remove volatile organic compounds (VOCs), demolition of one of the on-site buildings, and monitoring of groundwater and, if necessary, soil vapor. Contaminated subsurface structures will be excavated and removed. Fences and signs will be installed to limit access to the site while the remedy is underway, and existing restrictions will continue to limit the use of groundwater in the area.

Site Visit and Physical Hazards

On January 16, 1985, Richard Tuers and Tony Forti of the NYSDOH conducted an initial site inspection. In 1999, Jana Whalen of the NYSDOH visited the site and attended a public meeting on the remedial investigation. The meeting was organized by NYSDEC to solicit public input on the remedial investigation. In 2002, William Gilday and Rebecca Mitchell of the NYSDOH visited the site and surrounding area in conjunction with the preparation of this public health assessment.

Two buildings at the site are in serious disrepair and in danger of collapse. These are used for storage and are occasionally entered by the current tenant at the site and an associate. A third building, presently used for equipment and vehicle repair, also appears to be in a state of disrepair.

Demographics, Land Use, and Natural Resource Use

Demographics

The NYSDOH estimated, from the 2000 Census (US Bureau of the Census 2001), that 19,843 people live within 1 mile of the MacKenzie Chemical Works site. The age distribution of the area is similar to that of Suffolk County and slightly younger than that of New York State, excluding New York City (NYC). There were 4,623 females of reproductive age (ages 15-44 years) within 1 mile of the site. The area within 1 mile of the site has greater racial and ethnic diversity than the rest of the county or state (excluding NYC). Data from the 2000 Census indicate that a higher percentage of the population is living below the poverty level and the median household income is lower than the rest of the county (US Bureau of the Census 2002; see Table 1 for comparisons). In addition, there are five schools, Central Islip State hospital, and one nursing home within a mile of the site.

The NYSDEC and the EPA recently developed guidelines for identifying potential environmental justice communities. A potential environmental justice community is defined as a minority or low income community that may bear a disproportionate environmental burden resulting from industrial, municipal and commercial operations. A low income community is defined as one in which at least 23.59% of the population is living below the poverty level as defined by the 2000 U.S. Census. A minority community is defined as one having a minority population equal to or greater than 51.1% of the total population in an urban area or 33.8% of the total population in a rural area, as defined by the 2000 U.S. Census. If a community is found to be either low income or minority then it is defined as a potential environmental justice community. With a 69% minority population, the area within 1 mile of the MacKenzie Chemical Works site meets the criteria for a minority community. Consequently, it is considered a potential environmental justice community.

Table 1. Demographic comparisons for the MacKenzie Chemical Works site.
2000 Census Demographics New York State (excluding NYC) Suffolk County Area within 1 mile of the MacKenzie Chemical Works
Age Distribution
< 6 years 8% 9% 10%
6-19 years 20% 23% 22%
20-64 years 58% 58% 60%
> 64 years 14% 10% 8%
Race and Ethnicity Distribution
White 85% 85% 47%
Black 8% 7% 28%
Native American <1% <1% <1%
Asian 2% 2% 3%
Pacific Islander <1% 0% 0%
Other 2% 4% 16%
Multi-Racial 2% 2% 5%
Percent Minority* 18% 21% 69%
Percent Hispanic 6% 11% 37%
1999 Median Income $47,517 $65,288 $55,165
% Below Poverty Level 10% 6% 12%
* Minority includes Hispanics, African-Americans, Asian-Americans, Pacific Islanders, and Native Americans. US Bureau of Census 2001 and 2002


Land Use

The site is in a mixed use neighborhood immediately south of the LIRR. Various parts of the area are zoned for light industrial, commercial, and residential use. Several light industrial facilities are interspersed with single-family residential dwellings, churches, a school, a library, stores, and restaurants. Groundwater recharge basins are north of the LIRR sites, upgradient from the site.

Natural Resource Use

The major natural resource of use affected by this site is the sole-source groundwater aquifer. Groundwater, which is used for potable water supplies near the site, has been contaminated with VOCs from spills and leaks at the site. The area around the site is well drained and there are no streams or wetlands in the immediate vicinity of the site. The nearest water body is the Connetquot River about 1½ mile to the east-southeast. The site is approximately 5 miles north of Long Island's Atlantic Ocean shore.

Environmental Contamination and Other Hazards

Site conditions are characterized to evaluate if a site poses an existing or potential hazard to the exposed or potentially exposed population. This site characterization involves a review of sampling data for environmental media (e.g., soil, groundwater, air), both on-site and off-site. It also involves an evaluation of the physical conditions of the contaminant sources or physical hazards near the site which may pose an additional health risk to the community.

Contaminants selected for further evaluation are identified using the following factors:
  1. Concentrations of contaminants in environmental media both on-site and off-site;
  2. Field data quality, laboratory quality, and sample design;
  3. Comparison of on-site and off-site contaminant concentrations in environmental media with typical background levels;
  4. Comparison of contaminant concentrations in environmental media both on-site and off-site with public health assessment comparison values for (1) noncarcinogenic endpoints and (2) carcinogenic endpoints and drinking water standards; and
  5. Community health concerns.
The selected contaminants are evaluated in the Public Health Implications section of this PHA to determine whether exposure to these chemicals is of public health significance. The listing of a contaminant does not necessarily mean that it will cause adverse health effects from exposure at the concentrations detected.

This section includes a discussion of sampling data for various environmental media. All available chemical data from environmental analysis done in relation to the MacKenzie Chemical site were reviewed. Samples were analyzed for several categories of compounds, including VOCs, SVOCs, metals, polychlorinated biphenyls (PCBs), and pesticides. Most of the compounds were not detected or were present at low or background concentrations. Only those contaminants detected above background and/or health comparison values are listed in the summary tables of sampling data presented in Appendix B. The data summarized in the tables and discussed in this section were generated during several investigations. These include investigations by SCDHS in the 1980s and in 1993, by NYSDEC in 1992 and 1999-2000, and EPA's additional soil investigation in 2002.

On-Site Contamination

Several contaminants appeared with unusual frequency and at high concentrations across the site. In some cases, these chemicals appeared in more than one medium. For example, two volatile organic compounds-tetrachloroethene (PCE) and 1,2,3-trichloropropane (TCP)-appeared in wastewater discharge samples, in soil, in soil vapor, and in groundwater. The contaminants were also reviewed with respect to likely source and were screened against health-based comparison values. The screening values included those based on residential use of the property, which assumes a greater level of exposure than other uses. This screening indicated that two VOCs clearly prevailed as contaminants of concern at the site: PCE and TCP. A group of three SVOCs-9H-fluore-9-one, 2,4-dinitrofluorenone (DNF), and 2,4,7-trinitrofluorenone (TNF)-were also retained for further evaluation. The subsequent discussion and evaluation emphasizes these VOC and SVOC contaminants.

While PCE and TCP are the primary contaminants of concern for this PHA, three fluorenones (9H-fluore-9-one, DNF, and TNF) and a few other chemicals were detected at elevated levels and/or with frequency at the site. These include n-nitrosodiphenylamine, diphenylamine, adipic acid (hexanedioate), tocopherol (vitamin E), sesquiterpene (cadinene), and cobalt. The presence of these contaminants is consistent with historic production activities at MCW (Merck 1976). Miscellaneous organic acids, petroleum derivative compounds, alkanes, and substituted benzenes, possibly from MCW and/or from subsequent motor vehicle repair and dismantling activities, were also detected at the site. Shallow soil samples also contained several SVOCs, specifically polycyclic aromatic hydrocarbons (PAHs), which may be related to the recent use of the site for storage of paving equipment and debris. These contaminants should be investigated further during remedial decisions about the site.

A listing of chemicals used at the MCW site included the radioactive metals thorium and uranium, which were used in the laboratory at low levels. The radioactive materials were confined to the laboratory building. There is no evidence that they were used elsewhere at the site. The levels used did not warrant a license. Historical records of radioactive materials licensees in New York State did not show MCW to be a licensee. The EPA conducted a perimeter radioactive survey at the lab building in 2003 with negative results. Another survey is planned after demolition.

Source Areas: Leach Pits, Waste Lagoons and Subsurface Pipe

Historically, chemicals, surface spills, and wastewater were discharged into subsurface drainage structures such as lagoons, leach pits, and dry wells. These structures are significant sources of contamination at the MCW site. Source areas are typically localized concentrations of heavily contaminated liquids, soil, or sediments. They can include spill points or leach pits and can act as continuing sources of contamination to groundwater and soil vapor. Historic test results of liquids from a subsurface laboratory leach pool at the site indicate that the leach pool was a likely source of VOC contamination. Elevated levels of some metals, including lead and nickel, were also detected in the leach pool. A sample from one of two waste lagoons collected during the remedial investigation indicates the lagoon may have been a source of TCP contamination. Both lagoons were completely emptied and backfilled with clean fill in 1999. A sample collected from a broken subsurface pipe discovered beneath a driveway at the site also contained TCP, implicating it as a likely source of TCP. These data are summarized in Table 1B, Appendix B.

Surface Soil

During the remedial investigation in 1999, NYSDEC staff collected two soil samples near enough to the surface (0-6 inch depth) to assess the potential for direct contact with contaminants (NYSDEC 2000). One sample contained TNF at a concentration of 21.4 milligrams per kilogram (mg/kg). The area at and around the locations of these surface samples is now entirely covered with C&D debris and dirt piles.

The EPA collected surface soil samples from 10 locations in 2002. No VOCs were detected in these samples. The samples were not tested for the presence of fluorenones. A number of PAHs and other SVOCs were detected in the samples at concentrations near or slightly above the ranges commonly detected in environmental samples. This contamination is likely related to the ongoing storage of paving equipment and debris at the site.

Subsurface Soil

Many soil samples were collected from depths of about 1 foot to 40 feet below ground surface. Results from these samples document the presence of PCE and TCP at concentrations up to about 2.3 mg/kg and 680 mg/kg, respectively. In general, contaminant concentrations appeared to increase with depth for a few feet and then began to diminish with depth. High concentrations of TCP were detected, however, as deep as 40 feet. Fluorenone, DNF, and TNF were present at respective concentrations up to 15 mg/kg, 4 mg/kg, and 1,700 mg/kg in soil samples collected from about ½-foot to 2-foot depths. Soil sample results are summarized in Table 2B, Appendix B.

One soil sample collected from about 6 feet below grade near a subsurface drainage structure contained elevated concentrations of tentatively identified VOCs, as well as TCP. Another soil sample collected from about 10 feet below grade near a subsurface drainage contained significantly elevated concentrations of PAHs. In both cases, the contamination appears to be localized to an area and depth not available for human exposure.

Groundwater

Groundwater is beneath the site at a depth of about 50 feet below grade. Samples collected from groundwater beneath the site indicate the presence of several VOCs at concentrations greater than 10 times the respective New York State groundwater standards. These include the chlorinated compounds PCE, TCP, and trichloroethene (TCE). Several other VOCs, known as aromatic hydrocarbons, are often associated with petroleum contamination. They include benzene, toluene, ethyl benzene, and xylenes. These were also detected at similarly elevated concentrations in groundwater at the site, though with less frequency than the chlorinated VOCs. Groundwater was not tested for fluorenones. Groundwater profile samples (samples collected below the watertable depth of 50 feet below grade.) were also collected and analyzed. Table 3B in Appendix B summarizes groundwater results.

Soil Vapor

More than 50 soil vapor samples were collected from the site and tested for VOCs during the site investigations. These tests indicated the presence of a number of site-related VOCs in soil vapor beneath the site. The most frequently detected VOCs were chlorinated hydrocarbons: PCE, TCP, 1,1,1-trichloroethane (TCA), and TCE. These compounds were at concentrations up to 900,000 micrograms per cubic meter (mcg/m3), 2,200 mcg/m3, 21,000 mcg/m3, and 3,400 mcg/m3, respectively. Aromatic hydrocarbons (benzene, toluene, and xylenes) were also detected in soil vapor beneath the site, though with less frequency than the chlorinated VOCs. Table 4B in Appendix B summarizes soil vapor results.

Air

No air samples have been collected from the site. A portable photoionization detector (PID) instrument with a sensitivity of 0.1-0.2 parts per million used by NYSDOH during an April 30, 2002 visit did not indicate the presence of detectable levels of VOCs in air.

Structures; Sewer Catch Basin

No tests were done of dusts, surface residues, or materials in the on-site structures.

A sediment sample was collected from the bottom of an enclosed sewer basin in the street adjacent to the site. Although no characteristic contaminants of concern were detected, arsenic was detected at a significantly elevated concentration (2,180 mg/kg). Sampling results from MCW did not indicate arsenic as a contaminant of concern at the site. However, its presence at MCW would not be inconsistent with past operations, which reportedly included mixing of pesticides.

Off-Site Contamination

Surface Soil

Four surface soil samples were collected from a residential yard adjacent to the site and tested for VOCs, SVOCs, and metals. No VOCs were detected in the samples. Several SVOCs were detected in each sample, particularly PAHs. All of the levels detected for SVOCs were below health-based comparison values and/or were within the ranges commonly encountered in environmental samples, with one exception. A trace level of dichlorobenzidine, a chemical historically used in dyes but not commonly encountered in environmental samples, was detected in one of the samples. This chemical was not detected at the MCW site and the level detected in the off-site sample was slightly above a health-based comparison value. The levels of metals detected were below health-based comparison values and were within the ranges commonly detected in environmental samples.

Groundwater

Groundwater downgradient (southeast) from the former MCW site is contaminated with several VOCs, with TCP being one of the most predominant. TCP has been detected at concentrations up to 34,000 mcg/L in off-site groundwater. This is nearly 7,000 times the drinking water standard of 5 mcg/L. TCP has been detected at concentrations approaching 10,000 mcg/L at a distance of about one block from the site and at concentrations above 100 mcg/L at a distance of more than ¼ mile from the site. In general, TCP appears to migrate downward with distance from the site. According to data presented in NYSDEC's remedial investigation report, TCP contamination has penetrated from the water table (at about 50 feet below ground surface) to a depth of 120 feet within two blocks from the site and then to a depth of about 160 feet at a distance of four blocks from the site. The contamination appears to be within a narrow path, and concentrations can fluctuate considerably with time.

Private Water Supply Wells

Although the area is served by public water, at least two private wells potentially affected by groundwater contamination from the site are used for domestic purposes. One of these serves the residence immediately east of the site. This well was tested on six occasions between 1984 and 1999 (all but once by SCDHS). No detectable VOCs were found in any of these samples, except for a trace (1 mcg/L) of PCE in 1985. This concentration is below the maximum contaminant level (MCL) of 5 mcg/L for PCE in public drinking water supplies. A second private well used for domestic purposes, about two blocks downgradient from the site, was tested on four occasions between 1984 and 1993. Two of these samples had no detectable concentrations of VOCs, one had a detection of 1,1-dichloroethane (DCA) below the MCL, and one had detections of DCA and TCA below the MCL. The residence served by this well has since been connected to public water.

A well at the adjacent furniture warehouse property, which is upgradient from the site with respect to groundwater flow direction, was tested for VOCs in 1985. No contaminants were detected.

Although we are not aware of other private wells in the area, no complete well survey has been completed.

Public/Community Water Supply Wells

The Carleton Avenue well field, part of the Suffolk County Water Authority's (SCWA) public water supply system, is about ½ mile south-southeast of the site in a generally downgradient direction. The well field consists of a deep (750 feet) supply well that serves the surrounding community. This well is routinely monitored for VOCs, in accordance with NYSDOH's Part 5 drinking water regulations (NYSDOH 1993). Historic monitoring results from 31 samples collected from this well between 1981 and 2001 were reviewed. No VOCs were detected in these samples.

The New York Institute of Technology (NYIT) Islip campus is about ½ to 2 miles southeast of the MCW site. NYIT maintains a water supply well in an area about ½ mile east-southeast from MCW in the direction of groundwater flow. This supply well, which is believed to have been used for nonpotable purposes in the past, is presently inactive. A sample was collected for VOC analysis from this well in 1999. No VOCs were detected.

Soil Vapor

Because VOCs were detected at elevated concentrations in soil vapor beneath the site, soil vapor was tested for VOCs at several locations immediately south of the site near three homes. Several VOCs were detected in these samples, generally at concentrations considerably less than those detected on-site (see Table 4B, Appendix B). PCE was the most dominant VOC in off-site soil vapor in frequency and magnitude. PCE concentrations in soil vapor samples from nearest the occupied dwellings were less than the NYSDOH guideline value of 100 mcg/m3 for PCE in air (NYSDOH 2003), with one exception that slightly exceeded the guideline value. These data suggest that indoor air concentrations would likely be much less than the guideline value if subsurface vapors were to intrude into nearby basements.

In general, the off-site soil vapor results indicate that concentrations of VOCs in subsurface vapor diminish rapidly with distance from the site. This includes the area downgradient from the site with respect to shallow contaminated groundwater. Concentrations of VOCs in subsurface vapors did appear to increase with depth, however, suggesting the possibility of deeper sources near the site perimeter and/or some off-gassing from contaminated groundwater.



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