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PUBLIC HEALTH ASSESSMENT ADDENDUM

IRON HORSE PARK
BILLERICA, MIDDLESEX COUNTY, MASSACHUSETTS


ENVIRONMENTAL CONTAMINATION and PHYSICAL HAZARDS

Results reported in the Health Assessment completed in December of 1988 reflect environmental monitoring data available at that time. Since that time, further characterization of environmental media associated with the site has been conducted. The results reported in this addendum are those obtained during investigations conducted after those on which the initial health assessment was based.

The tables in this section list the environmental contaminants of concern. This concern is based on the comparison of contaminant levels detected on or near the site with those levels to which exposure has been associated with no adverse health effects. These comparison values include Ambient Water Quality Criteria, Environmental Media Evaluation Guides and EPA's Drinking Water Life Time Health Advisories (LTHA) which are values derived from animal and human studies for which non-cancer adverse health effects were investigated. Ambient Water Quality Criteria are standards established by federal environmental agencies for guidance with respect to effects of surface water pollutants on human health and safety of aquatic organism consumption. Environmental Media Evaluation Guides are those levels developed by ATSDR for health assessment purposes. For sediment, they are those values for which no non-cancer health effects are known to occur assuming ingestion of large amounts by children on an infrequent basis or by adults who may frequently and inadvertently ingest small amounts. Acute exposure in any media is assumed to occur for short periods of time (less than 14 days). Chronic exposure is assumed to occur constantly for periods greater than one year. Maximum Contamination Levels are established by the Safe Drinking Water Act as the lowest attainable level by current technology known to have no adverse health effects based on an ingestion rate of two liters per day.

Cancer Risk Evaluation Guides (CREGs) are used for compounds which are known or suspected to be carcinogenic based on either animal or human studies. CREG levels are those for which exposure is associated with an excess cancer risk of one in a million. It is important to note that the presence of hazardous contamination levels is not indicative that actual exposure to site-related contaminants is occurring. The likelihood of hazardous exposure and the subsequent health ramifications are disclosed later in this Public Health Assessment.

The data tables in this section include the following acronyms:

ND -Contaminant not detected
NA -Comparison value for compound in specific environmental media is not available
CREG -ATSDR Cancer Risk Evaluation Guide
AWQC -Ambient Water Quality Criteria
LTHA -EPAs drinking water Lifetime Health Advisory
EMEG(a) - Environmental Media Evaluation Guide (acute)
EMEG(c) -Environmental Media Evaluation Guide (chronic)
MCL -Maximum Contamination Levels
ppm -parts per million (milligrams per kilogram soil)
ppb -parts per billion (micrograms per liter of water)

A. ON-SITE CONTAMINATION

The majority of on-site contaminants detected in monitoring conducted after 1986 were found in surface water and sediment in Content Brook and are summarized in Tables 1 and 2 (Appendix 3). Since Richardson Pond is north of the MBTA railroad tracks which constitute the site's northern boundary, this surface water body will be considered off-site. The highest levels of ground water contamination were detected in those wells drilled on the landfill near the brook (Table 3, Appendix 3).

Air monitoring was conducted at the landfill grounds by MDEP on May 23, July 2 and July 16 of 1990 and the results are presented in Table 4, Appendix 3. It should be noted that these contaminants were detected in a gas collection system that is normally closed but was opened briefly for monitoring purposes. Toluene (.281 ppm) was detected above areas where ground cover erosion was observed. Methane was also frequently detected, however, the instrumentation used for methane monitoring did not provide quantitative measurements.

B. OFF-SITE CONTAMINATION

The highest levels of off-site contamination were detected in Richardson Pond and are summarized in Table 5, Appendix 3. A leachate seep was observed to be flowing from a peninsula immediately north of the residential section of the landfill into Richardson Pond. The highest levels of off-site ground water contamination were detected in wells drilled on the peninsula. Arsenic was detected at elevated levels in ground water sampled from a monitoring well approximately one half mile east of Content Brook (Table 6, Appendix 3). No VOC contamination was detected in off-site surface water sampled from Content Brook, downgradient of the landfill, however, arsenic (82 ppm) was detected in Content Brook sediment sampled 700 feet east of Gray Street (Table 7, Appendix 3).

Contamination was detected in tissue from mammals and fish caught near the site and the levels detected are presented in Table 8, Appendix 3. PCBs were detected in different fish native to Long Pond, which is hydraulically upgradient to the site. Tissue from fish caught in Content Brook east of Gray Street had lower PCB contamination levels.

C. QUALITY ASSURANCE AND QUALITY CONTROL

Elevated benzene levels were detected in recent monitoring of shallow overburden ground water southwest of the landfill. These data support those reported in an earlier remedial investigation (June, 1986) that were initially thought to be spurious.

Insufficient background contaminant and meteorologic data was collected during the air monitoring conducted by MDEP at the Shaffer Landfill in May and July of 1990. In addition, much of the VOC contamination data, which was collected from gas collection wells, may not have been representative of actual ambient air conditions. As a result, more extensive air monitoring is required before health risks related to ambient air exposure at the landfill can be characterized.

The conclusions presented in this public health assessment addendum are based on the data reviewed. The validity of these conclusions is dependent on the quality of the data provided.

D. PHYSICAL HAZARDS

Trespassers on the landfill may sustain injury from falling since the slope of the two hills situated on the landfill is relatively steep. This is especially a concern on the north face of the residential section. It is possible that the fencing constructed at the site will limit access to the site thus reducing the possibility of physical injury at the site. Richardson Pond was not adequately fenced but the majority of the pond appeared marsh-like and not likely to pose a significant risk for drowning. The brook and canal associated with the landfill are relatively shallow and the possibility of drowning in these surface water bodies is remote.

E. TOXIC CHEMICAL RELEASE INVENTORY DATA

To identify possible facilities that could contribute to the air, surface water and soil contamination near the Shaffer Landfill, the Toxic Release Inventory (TRI) data base was searched. TRI is developed by the USEPA from the chemical release information provided by certain industries. No releases of contaminants that were detected at the landfill in elevated amounts were reported. A summary of contaminants released to air by Billerica industries are presented in Table 9, Appendix 3.

PATHWAYS ANALYSES

In this section, various transport means of environmental hazards from the contamination source to human receptor populations are presented. If such migration and uptake by some members of the population is known to occur, the environmental pathway is considered to be complete. No complete exposure pathways were identified at the site. Potential exposure pathways are summarized in Table 10, Appendix 3. The presence of an environmental pathway, however, does not necessarily mean that hazardous exposure has occurred or is ongoing. The extent of public health risk depends not only on the presence of exposure but also on the toxicity of the contaminants and the dosages to which the receptor population is exposed. These two factors are discussed in the Public Health Implications section.

A. COMPLETED EXPOSURE PATHWAYS

No complete exposure pathways associated with the site could be identified.

B. POTENTIAL EXPOSURE PATHWAYS

Surface Water

Some potential exists for ingestion of contaminated surface waters given the unrestricted access to both Richardson Pond and Content Brook. The oily and rust colored appearance of these waters, however, renders the possibility of such exposure extremely remote. Dermal contact with these waters is also possible. Leachate is produced when precipitation permeates the ground cover of the landfill and dissolves landfill contents. This is possible at the Shaffer Landfill since erosion and cracking have been observed in the cap of the landfill. The leachate then migrates downward into ground water which then carries contaminants horizontally along hydrogeological gradients. The leachate outbreaks at Richardson Pond and Content Brook are, in all likelihood, the result of lateral movement of leachate in ground water towards these surface water bodies. Maximum ground water contamination has been detected in those samples drawn from wells drilled in immediate proximity to the leachate seeps, which were observed at both Richardson Pond and Content Brook. These water bodies are topographically and hydraulically downgradient of the landfill.

The direction of ground water flow has been well characterized at the site and is attributable to the bedrock topography and the locations of surface water bodies in the immediate vicinity of the landfill. Three areas with differing directions of ground water flow have been identified at the landfill. In the western region of the landfill, ground water flows from the southwest across the residential section towards Richardson Pond in the northeast. Ground water flow in the central region of the landfill, which encompasses portions of both the residential and commercial sections, is towards Richardson Pond to the north and Middlesex Canal to the south. The hydraulic gradient in this area is relatively flat with ground water flow averaging less than 0.1 feet per day. The easternmost section of the landfill comprises the third region of ground water flow. This occurs in an easterly direction between two bedrock peaks situated northeast and southeast of the landfill. The steepest hydraulic gradient has been measured in this area with ground water flow toward Content Brook estimated at .39 feet per day.

The remedial alternative proposed and ultimately selected by USEPA in June of 1991 will reduce the possibility of exposure to leachate generated at the landfill. The selected plan proposes reconstruction of the landfill cap in order to reduce the potential for leachate production. This construction includes the removal of the existing top soil layer and the addition of low permeability soil providing complete coverage of both landfill sections. An impermeable textured membrane layer will be placed over the low permeability soil layer. This layer will be covered with a six inch layer of water-permeable soil for drainage purposes and a 12 inch top soil layer. A non-woven filter fabric will be placed between these two soil layers and the top soil layer will be reseeded. The tops of both landfill sections will be regraded to achieve a 5% gradient. Since excavation and transport of contaminated materials is proposed, proper containment measures must be implemented in order to minimize the potential for release of these materials and subsequent residential exposure.

The proposed installation of a leachate collection system around the periphery of the landfill addresses the reduction of the possibility for leachate migration into surface water. It is proposed that the system will be designed to accommodate leachate that would be produced during periods of extensive rainfall and that since the system is gravity fed, leachate collection will cease when its capacity is reached. It is anticipated that the reduction of leachate formation and migration into surface water will allow for the decrease of existing surface water contamination via natural processes.

Ambient Air

It is possible that individuals trespassing on the landfill grounds could be exposed to landfill gases. These gases are routinely generated at landfills as a result of waste decomposition and fissures in the cap allow for their escape. When climatic conditions have allowed, bubbling has been observed in these fissures.

VOC contamination has been detected in air monitored at ground level above openings in the gas collection system. Air contamination levels, however, have not been determined either off-site or on-site at heights of three to six feet above ground surface where normal air intake would occur. In addition, an insufficient number of samples monitoring background contamination levels were taken during the recent on-site monitoring. It is therefore impossible to determine if human inhalation of site-related contaminants is a current concern.

The possibility of gas migration from the landfill into ambient air will be reduced by the proposed reconstruction of the landfill cap and improvements in the gas collection system. A fence on three sides of the site was constructed in October of 1991. This fence may discourage trespassing on the site and reduce the possibility of subsequent exposure to on-site air contaminants.

Under conditions where vertical migration of landfill gases is impeded, lateral migration of these gases through soil is possible. This migration can occur in the absence of an adequate venting system which would allow for the controlled burning of decomposition products. In addition, the prevalence of soils with low permeability in proximity to the site would also prevent the upward migration of these gases which are generally lighter than air. Until off-site subsurface soil monitoring for landfill gases is conducted, it is not possible to determine the extent to which this migration is occurring. The proposed upgrading of the existing gas collection system will also decrease any potential for lateral gas migration through subsurface soil.

Food Chain

Ingestion of PCBs and mercury, which are known to accumulate in fish, is probably occurring since fishing activities in nearby waters has been reported. Bioaccumulation of PCBs has been observed in fish tissue sampled from those caught in surface waters near Iron Horse Park. As reported in the initial Health Assessment for this site, PCB contaminated sediment was detected in a catch basin in the northwestern sector of Iron Horse Park, away from the Shaffer Landfill. The highest levels of PCB contamination in fish, however, were detected in those caught in Long Pond upgradient to Iron Horse Park. PCB contamination was also detected in tissue from fish caught at the juncture of Richardson Pond and Content Brook. Given that elevated PCB levels were detected in fish distant to the site and that on-site sediment PCB contamination was confined to catch basins, environmental PCB migration pathways from the site are difficult to establish.

Mercury was detected in leachate monitored in surface water at Content Brook. Mercury is also known to bioaccumulate in aquatic organisms native to mercury contaminated waters. Since mercury was detected in tissue from fish caught in waters upstream and downstream of the landfill, the extent of mercury bioaccumulation in fish that is attributable to site-related contamination can not be assessed at this time.

Ground Water

It was initially believed that a hydraulic connection existed between Richardson Pond where leachate from the landfill was observed and a cluster of municipal drinking water wells, 4,000 feet northeast of the pond in Tewksbury. The extensive hydrogeologic characterization which was recently conducted, demonstrates that ground water flow from the landfill is not toward the well cluster. These findings are substantiated by the detection of bedrock elevations between the pond and the well field. In addition, VOC monitoring, which is conducted biannually by MDEP at all municipal drinking water supplies, detected no significant VOC contamination at these Tewksbury wells. It is therefore extremely unlikely that exposure to Shaffer Landfill contaminants via ingestion of Tewksbury municipal waters is ongoing.

The juncture of Richardson Pond and Content Brook has been demonstrated to be an area where ground water is recharged by surface water. This recharge area is also downgradient of an on-site monitoring well where maximum levels of benzene, vinyl chloride and arsenic were detected in shallow overburden ground water. No vinyl chloride was detected in ground water downgradient of this recharge area and benzene levels monitored downgradient were significantly reduced. It is possible that dilution of ground water contaminants is occurring in this area.

Arsenic may, however, may be migrating via ground water in significant amounts from the site since elevated arsenic levels were detected in deep overburden and bedrock ground water monitored 0.5 miles downgradient of the site. Elevated mercury levels were also detected in ground water at this point, however, there is no evidence of mercury contamination in on-site ground water.

Private wells were identified on Gray Street in proximity to the area where elevated arsenic and mercury were detected in ground water. These wells were monitored for the presence of environmental contamination and elevated iron and manganese levels were detected. As a result, these wells were shut down in 1984 and the residents were provided with municipal water (1). There have been no other private wells identified in the area.

Although ground water use at or near the landfill is not currently ongoing, future health risks associated with such exposure are addressed in the remedial plan. All alternatives propose institutional controls prohibiting future use of on-site ground water. Compliance with these controls will reduce the likelihood of future exposure to ground water contamination. The extent of this contamination can be accurately assessed since all of the alternatives with the exception of that proposing no action call for continued site-related ground and surface water monitoring.

Soil

In the absence of sufficient vegetative cover at the landfill, contamination migration via soil erosion could occur. The extent to which this is actually ongoing is uncertain since no monitoring for soil contamination has been conducted at the landfill. Such monitoring would further compromise the structural integrity of the existing cap. Future migration of contaminants via soil erosion is addressed by the proposed improvements in the surface drainage system at the landfill.

The possibility of site contamination migration would increase in the event of flooding in the area. Residences east of the landfill on Gray Street have been determined to lie within the 100-year flood plain and as a result dermal contact with soil contaminants during flood periods may be possible. Landfill soils can become airborne as a result of meteorologic, vehicular or pedestrian disturbances. Since soil contamination has not been characterized at the landfill, it is not possible to assess the extent of this exposure route.

PUBLIC HEALTH IMPLICATIONS

In this section the potential health risks posed to the public as a result of possible exposure to site contaminants are evaluated. In addition, available health data pertinent to the site are presented. The possible impact of environmental exposure on disease rates is discussed in this section. Finally, citizen concerns specifically voiced to public health officials are addressed.

A. TOXICOLOGICAL EVALUATION

    1. Ground water

Results of epidemiologic studies have indicated that regular ingestion of elevated arsenic levels would increase an individual's risk for skin cancer development. In addition, recent epidemiological studies have suggested that ingestion of arsenic may be associated with an increased risk of bladder, kidney, lung and liver cancer development. Animal studies have demonstrated an association between vinyl chloride ingestion and increased risk of liver and lung cancer development. Ingestion of benzene has also been shown in animal experiments to enhance risk of lymphoma development. Ingestion of TCE has been associated with increased risk of liver cancer development in mice and with increased leukemia development in male rats. Insufficient quantitative data exist that associate human ingestion of vinyl chloride, benzene and TCE with increased risk of cancer development in humans. Consequently, estimates of human cancer risk resulting from such exposures are derived from animal study findings. Arsenic, vinyl chloride, benzene and TCE levels have been detected in ground water proximal to the leachate outbreaks which, based on either animal or human studies, would impart an increased risk of cancer development if ingested on a regular basis.

Benzene and TCE were not detected in on-site ground water at levels that pose a non-cancer health concern. Chronic exposure via ingestion to vinyl chloride at levels below those detected in on-site ground water has been associated with increased risk of non-cancerous liver disease development in rats.

Arsenic was detected in on-site ground water at levels above which human studies have associated ingestion with numerous adverse non-cancerous health effects. Acute ingestion of arsenic contaminated ground water detected near the leachate outbreaks in sufficient amounts would cause liver and kidney damage, vascular and skin lesions, gastrointestinal irritations, anemia and neuropathy. The severity of these effects increase with prolonged exposure via ingestion. The most sensitive indication that acute arsenic poisoning has occurred is the development of pigmented, corn-like lesions.

The chronic and acute health effects associated with ingestion of on-site waters would occur if contaminant levels were available in a drinking water source. Access to ground water either associated with the site or the leachate seeps is currently not attainable and no evidence exists that demonstrates that this ground water was used as a drinking water source in the past.

Levels of contamination detected in ground waters distant to the site do not pose an acute health concern at this time. Ingestion of some off-site ground waters, however, may result in chronic health effects if regularly ingested. If individuals were to regularly ingest arsenic levels detected in ground waters one half mile east of Content Brook they might be at increased risk of skin lesion development and skin cancer. There is, however, no evidence that this is occurring. Currently, there are no other adverse health effects associated with ingestion of these arsenic levels. There is no evidence that these waters were consumed in the past and no known use of these waters is occurring at this time. Levels of TCE detected in ground water northwest of the landfill would pose a cancer risk if ingested on a regular basis. There is no evidence that this is currently occurring or that these waters were used as a drinking water source in the past.

    2. Surface water and associated sediment

Given the poor appearance of the leachate outbreak detected at Content Brook, any exposure to leachate contaminants such as mercury, lead or arsenic would not occur frequently. Kidney damage that was observed in mercury-exposed animals would not occur in humans at the level of mercury exposure associated with incidental leachate ingestion.

The lead exposure that would occur as a result of leachate ingestion may be sufficient enough to cause temporary disturbances in the production of hemoglobin and anemia may ensue. This health effect is that which is most readily observable as a result of lead exposure. Neurologic deficits, abnormal Vitamin D metabolism, renal dysfunction and gastrointestinal ailments were observed in studies of children whose blood lead levels indicated chronic environmental lead exposure. Chronic exposure to elevated environmental lead levels has been demonstrated to elevate blood pressure in adult males. It is unlikely that these chronic health effects could be attributable to leachate contaminant exposure since the probability of regular exposure via ingestion of these waters is remote.

Incidental ingestion of lead levels detected in surface waters associated with the site would not alone acutely impact human health. There are, however, other sources of lead to which individuals are exposed on a daily basis. Sources of daily environmental lead exposure include air, drinking water and food. Casual ingestion of lead contaminated surface water would add to the level of environmental lead exposure experienced by the individual. The impact of such exposure on blood levels would be dependent on the extent of additional lead exposures.

Development of gastrointestinal and neurologic disorders indicative of arsenic poisoning would result if large quantities (e.g. greater than a quart) of contaminated surface waters from Content Brook were ingested. Given the distasteful appearance of these waters, the possibility of such poisoning occurring is extremely remote.

Skin lesions associated with arsenic intoxication may develop as a result of contact with arsenic contaminated surface waters or sediments of Content Brook. The extent of dermal contact with arsenic contamination that is required to precipitate this symptomatology has not yet been established. Elevated arsenic levels were detected in sediment monitored from Content Brook as far as 2,000 feet east of the site. Due to the variable nature of exposure that may be possible during flood periods, the health impacts associated with dermal contacts to site-contaminants under these conditions, can not be accurately assessed.

    3. Food Chain

No acute health effects have been associated with ingestion of PCB levels detected in fish caught from Long Pond. The risk of liver cancer development resulting from such exposure can not be accurately determined at present. This uncertainty arises from the interpretation of animal study findings which indicate a possibility of elevated cancer risk resulting from PCB exposure. Human studies, however, do not demonstrate an increased cancer risk resulting from such exposure. The mercury levels detected in fish caught from site-associated waters are not high enough to cause any health concern.

    4. Air

Actual exposure to ambient air contamination at the landfill is difficult to assess since no valid quantitative air monitoring was conducted at the landfill. Furthermore, monitoring which was conducted on the site was done at ground level and not at the height of an individual's nose and mouth. Also, since air monitoring at residences proximal to the site has not yet been conducted, health impacts resulting from exposure to off-site ambient air can not be assessed. The hazards associated with exposure to lateral gas migration through subsurface soils also can not be accurately assessed until monitoring for such gases is conducted.

B. HEALTH OUTCOME DATA EVALUATION

As reported by the MDPH in 1988, lung cancer mortality was increased among Billerica male residents living within a one mile radius of Iron Horse Park relative to the remainder of the town. Recent cancer incidence data (1982-1988) for the entire town of Billerica was reviewed. There were 90 new male lung cancer cases reported during this period. Among female residents from Billerica, there were 50 new lung cancer cases reported. These numbers as a whole are significantly elevated in comparison to what would be expected based on the statewide lung cancer experience. Based on state age and sex specific lung cancer incidence rates for this period, 68 male and 36 female new lung cancer cases would be expected.

Census tract-specific lung cancer incidence was also determined for Billerica and the results are presented in Table 11, Appendix 3. Also presented in this table are the numbers of lung cancer cases that would be expected in these areas based on statewide age and sex-specific cancer rates. Lung cancer rates in males residing in four of the five Billerica census tracts were elevated. The elevation of lung cancer in males was statistically significant in two census tracts that were adjacent to Iron Horse Park. A statistically significant elevation of lung cancer incidence was also observed among females residing in the census tract immediately south of the site. These data indicate that the relationship between environmental exposure to contaminants detected at Iron Horse Park and lung cancer risk should continue to be investigated.

A report of cancer incidence rates for the Tewksbury census tract immediately north of the Shaffer Landfill was released by the Community Assessment Unit within MDPH in March of 1989. From 1982 to 1986, an increase in lung cancer incidence was observed among male and female residents of this census tract, relative to that which would be expected based on the statewide lung cancer rates. There were 21 and 11 new lung cancer cases in men and women respectively. Based on the statewide experience, 11 male and 5 female new lung cancer cases would be expected. The increase in both male and female lung cancers observed in Tewksbury achieved statistical significance.

Two additional years of cancer incidence data for Tewksbury from 1982 to 1988 were recently reviewed. These data indicate that there were 23 new male lung cancer cases and 16 new female lung cancer cases during this period in the Tewksbury census tract immediately north of the landfill. Based on the statewide lung cancer experience, there would be 14.8 new cases and 7.3 new cases expected for males and females respectively. The increase in the number of male lung cancer cases compared to what would be expected based on the statewide experience was not statistically significant. The number of new female lung cancer cases observed from 1982 to 1988 in this area continues, however, to remain significantly elevated.

Risk factors for lung cancer development include tobacco use as well as asbestos and radon exposure. Findings of investigations conducted in laboratory or occupational settings have associated exposure to arsenic, vinyl chloride, TCE, chromium, nickel and beryllium via inhalation with a possible increased risk of lung cancer development.

It is possible that inhalation of windborne asbestos particles disseminating from the inadequately capped asbestos landfill in Iron Horse Park may have occurred in the past. Clinical studies have identified immunologic responses specific for asbestos exposure (7). Further evaluation of existing data on individuals diagnosed with lung cancer should allow health assessors to determine if clinical evaluations are warranted.

Although vinyl chloride, TCE and arsenic have been detected in environmental media associated with the landfill, no human exposure pathway has yet been identified that would result in exposure to hazardous levels of these contaminants. Complete ambient air monitoring at the landfill as well as in residential areas proximal to the site will, however, allow for a more accurate assessment of lung cancer risks associated with exposure to landfill gases at the site. In addition to the conduct of the investigations mentioned above, consideration of smoking and occupational histories as well as indoor radon determination of residences in proximity to the site are necessary in order to determine the extent of lung disease attributable to environmental exposure.

C. COMMUNITY HEALTH CONCERNS EVALUATION

We have addressed each of the community health concerns about health in the following manner:

1. Are the Tewksbury Municipal Wells at risk of being infiltrated by contaminants migrating form the landfill?

It was reported in the Phase 1A Remedial Investigation which was released by the USEPA in 1987 that pump tests have indicated a hydraulic connection between the northeastern corner of Richardson Pond and the nearby Tewksbury Public Wells. This possibility was more extensively investigated and data released by the USEPA in 1991 demonstrate that it is unlikely that the wells could be contaminated by ground water migrating from the landfill. This finding is substantiated by ground water flow studies which indicate that ground water flow from the landfill is to the east away from the nearest Tewksbury well cluster. Furthermore, no contaminants were detected in monitoring wells drilled between Richardson Pond and the Tewksbury wells. Finally, the MDEP has been monitoring all municipal drinking water sources in the Commonwealth for VOC contamination and none was detected in the Tewksbury wells. Continued monitoring of water drawn from both the monitoring wells and the municipal wells will assure future safety of Tewksbury municipal water consumption.

2. Will waters drawn from private wells near the landfill be safe to drink in the future?

In 1984, four residential wells on Gray Street, near the landfill, were shut down due to their proximity to the landfill. These wells were monitored and elevated levels of iron and manganese were detected in two of these wells. These residences have since been supplied with municipal water. Since these wells are east of the landfill and possibly in the direction of ground water flow from the landfill, consumption of this ground water is not recommended. No other private wells have been identified in the area.

3. Are municipalities served by waters drawn from the Shawseen River at risk of exposure to contaminants migrating from the landfill downstream to this water source?

No. Contamination was detected in Content Brook downstream of the leachate outbreak. The possibility of contamination migrating from the landfill to the Shawseen River is remote since non-detectable amounts of contaminants would have to travel a considerable distance for this to occur. The MDEP also monitors public water supplies regularly to assure their safety for consumption.

4. Are children wading in ponds near Gray Street and Content Brook at risk of exposure to landfill contaminants?

Since monitoring of these surface water bodies has not been conducted, it is not possible to state with certainty that the opportunity for exposure to landfill contaminants does not exist. As stated previously, however, no landfill associated contamination has been detected in Content Brook downstream of the leachate outbreak at the landfill. Exposure to landfill contaminants via dermal contact with or incidental ingestion of these waters is therefore unlikely. Monitoring of these waters will, however, enable environmental and health officials to more accurately assess whether or not exposure to landfill contaminants via these routes is ongoing.

On July 19, 1994, this Public Health Assessment Addendum was released for public review and commentary. No comments were received during the comment period ending on August 18, 1993.



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