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The initial health assessment and related amendment for Iron Horse Park were completed in December of 1988 and amended in April of 1990 (see Appendix 1), respectively. These health assessments identified numerous data gaps which were addressed in subsequent investigations released by the United States Environmental Protection Agency (USEPA). Health concerns detailed in this addendum are based on findings of these monitoring activities conducted on or near the Shaffer Landfill at Iron Horse Park.

Benzene and arsenic were detected in leachate outbreaks flowing into Richardson Pond, north of the site, and a hydraulic connection was initially believed to exist between this water body and ground water charging the Tewksbury municipal drinking wells, 4,000 feet north of the site. Extensive hydrogeologic characterization subsequently conducted in the area indicate that migration of these contaminated waters towards the Tewksbury municipal well fields is unlikely. Furthermore, biannual volatile organic compound (VOC) monitoring of all municipal water supplies conducted by the Massachusetts Department of Environmental Protection (MDEP) detected no site-related VOC contamination in these wells.

Polychlorinated biphenyls (PCBs) which were detected in site-related sediments were also detected in fish tissue monitored in samples harvested from surface waters near the site. Maximum PCB levels in fish were, however, detected in those caught in waters hydraulically upgradient to the site.

Air monitoring from the gas collection system at the landfill indicated the possibility of exposure to VOCs via ambient air at the landfill. This monitoring was, however, of a preliminary nature and as a result, the health risks posed by such exposure can not be accurately assessed at this time. No evidence exists that indicates whether lateral migration of landfill gas through subsurface soil is ongoing. The possibility of this occurrence, however, can not be ruled out at this time.

Investigations by the Massachusetts Department of Public Health (MDPH) have reported elevations of lung cancer incidence and mortality rates in areas surrounding the site. Lung cancer risk factors associated with the site as well as radon exposure, occupational exposures and lifestyle factors should be investigated in order to assess the impact of site-related contamination and past exposures on this health outcome. No current exposure to contaminants detected at Shaffer Landfill associated with lung cancer risk can be identified at this time.

Based on the data reviewed for this public health assessment addendum, ATSDR has concluded that the Shaffer Landfill part of the Iron Horse Park site is of indeterminate public health hazard due to the lack of quantitative air monitoring data collected at the landfill. Although results of preliminary monitoring indicate the presence of VOCs in the gas collection system, actual levels of these compounds have not been adequately measured in ambient air and as a result, the health risk associated with exposure via inhalation at the landfill can not be assessed. As stated in the April 4, 1990 Amended Health Assessment, however, the Iron Horse Park site, as a whole, poses a public health hazard because past exposure to asbestos may have occurred through inhalation of fugitive dusts. This exposure may result in adverse health effects. Because of probable past exposure to asbestos and because the review of health outcome data indicate a possible excess occurrence of lung cancer, the Panel determines that consideration of biologic indicator testing for asbestos exposure (biomarkers) and a lung cancer cluster investigation are indicated. In addition, the Panel determined that community and health professions education are needed.



The Shaffer Landfill site is situated in Iron Horse Park in Billerica MA. Iron Horse Park was added to the National Priorities List (NPL) in 1984. The landfill is a rectangular plot extending eastward from the remainder of the Iron Horse Park site, approximately 1,000 feet in width and 4,200 feet in length. The Middlesex Canal flows easterly along the southern boundary of the landfill and railroad tracks currently owned by the Massachusetts Bay Transit Authority (MBTA) run easterly along the northern boundary of the landfill. Richardson Pond is situated immediately north of the railroad and also extends the length of the landfill. Content Brook, which comprises the eastern boundary, drains Richardson Pond, merges with the Middlesex Canal and then runs northeasterly through residential areas until it finally drains into the Shawseen River, 2.25 miles east of the site (Figure 1, Appendix 2).

The above-ground landfill is comprised of two unlined sections with elevations of approximately 75 feet above ground level. The westernmost section, termed the residential section, encompasses approximately 24 acres. Immediately north of the residential area, a small peninsula extends into Richardson Pond. The commercial area in the eastern section of the landfill was so termed because of the past extensive use of this area by commercial waste removal companies. Leachate seeps have been observed flowing from both of these areas (1). One outbreak flows from the residential section into the southwest sector of Richardson Pond and another runs from the eastern toe of the landfill into Content Brook.

The landfill was in operation for more than forty years. In 1968, town regulations were enacted requiring that refuse be buried above the water table and that open burning activities cease. Landfill owners failed to comply with these regulations and after issuance of numerous citations and administrative orders by the Massachusetts Department of Environmental Quality Engineering [now the Massachusetts Department of Environmental Protection (MDEP)], the owners of the landfill were sued for non-compliance with the Commonwealth's waste disposal regulations. The litigation ultimately resulted in the cessation of landfill operations in April of 1986.

Closure plans, established by a Final Judgement signed in June, 1984, are currently in varying stages of completion. The clay cap that has been put in place does not meet with either Massachusetts regulations or judgement conditions with respect to both depth of clay cover or depth of top soil layer. In some instances, the soil layer is inadequate to support vegetative growth. As a result, the potential for erosion in sparsely covered areas is increased. It has also been reported that due to flaws in the cover design, the clay layer may be prone to frost heaving causing localized fracturing of the cover. This could lead to increased water infiltration, leachate production and landfill gas escape to ambient air. Other closure measures contained in the consent agreement included the installation of a landfill gas collection and treatment system which has been completed and is undergoing final adjustments and a leachate collection system which is still being designed.

Directions of ground water flow and contamination were incompletely characterized at the time the initial Iron Horse Park Health Assessment was conducted. Concern with the potential for contaminated ground water migration towards the Tewksbury municipal well fields, 4,000 feet north of the site, was also raised in this report. Finally, the initial health assessment for this site demonstrated the potential for migration of some site associated contaminants through the food chain. There was, however, no food chain monitoring conducted up to that point and it was uncertain if contamination migration through the food chain near the site was actually occurring. Extensive ground water monitoring, hydrologic characterization and food chain monitoring were conducted during the Phase 1C remedial Investigation for the Shaffer Landfill. Also since the completion of this report, a Record of Decision (ROD) was signed in June of 1991, selecting a plan for the remediation of the Shaffer Landfill Operable Unit of the Iron Horse Park site. This plan included the installation of a site perimeter fence, total reconstruction of the landfill cap, installation of a leachate collection system and upgrading of the landfill gas ventilation system. A fence was erected on three sides of the site in October of 1991. It is reported by Massachusetts environmental regulatory officials that the unfenced area is not accessible due to the large areas of wetland and dense undergrowth. This addendum is based on the results of recent investigations and selected remedial plans.


The Shaffer Landfill was visited on February 26, 1991 by Don McElroy, USEPA Remedial Project Manager, Susanne Simon, ATSDR Region I Representative and William C. Strohsnitter, MDPH Environmental Analyst. Neither site security nor signs prohibiting trespassing on the site were evident. A gate approximately 8 feet in height was erected to prevent vehicular access. Trespassing was evident and numerous activities are occurring on the landfill grounds. Indicators of site encroachment include spent shotgun shells, all-terrain vehicle tracks and horse hoof prints. Two 55-gallon drums whose contents were unidentified and two derelict automobiles were observed at the eastern end of the landfill.

Rust colored water at the site's northern and northeastern edge was observed and could possibly be indicative of leachate migration. The standing water at the northeastern corner of the site was external to Content Brook and contained an oil film at its edges. Some portions of Content Brook were accessed, however overgrowth of vegetative brush prevented complete survey of these surface waters.

A storm fence, which was situated between the railroad tracks and Richardson Pond was in disrepair and did not prevent approach to Richardson Pond. This surface water body was overrun with marsh weeds and, in all likelihood, would not support recreational aquatic activities such as fishing or swimming.


The area surrounding the north, northeastern and southeastern sections of the landfill is predominantly wetlands. The remainder of Iron Horse Park lies to the west of the landfill. Residential housing is developed immediately south of the landfill, east of Pond street. Gray Street, 400 feet east of the landfill, also contains residential housing. Sensitive receptor populations in the area include those children attending the Tewksbury Youth Center, 4,000 feet north of the landfill (1). The closest nursing home facility is two miles south of the landfill on Boston Street. Most of the drinking water needs of the Billerica residents are served by the Concord River at a point one mile upstream of its juncture with the Middlesex Canal. Four residences located on Gray Street, one quarter of a mile east of the landfill were served by their own private wells. These wells were removed from service upon closure of the landfill (1). The Town of Tewksbury's drinking water needs are served by several ground water well clusters. The closest of these clusters is located approximately 4,000 feet northeast of the landfill.

Surface water near the area is also known to be used for fishing activities. Such activities have been reported to occur in both Content Brook and Long Pond, which drains into Richardson Pond. Long Pond is situated approximately 1,000 feet north of Richardson Pond. Swimming has been reported to occur in Long Pond. Rabbit hunting has been observed in woods proximal to the Shaffer Landfill (1). The MDEP reports that hunters were twice seen during fence construction activities conducted between September 21, and October 21, 1993.


At the request of the Billerica citizens and their state legislators, the Community Assessment Unit (CAU) within the MDPH conducted an investigation of cancer mortality in the area surrounding Iron Horse Park. This report was completed in 1988. Townwide cancer incidence data for Billerica from 1982 to 1988 were recently reviewed for this addendum in order assess current rates of the lung cancer experienced in Billerica. An investigation of census tract-specific cancer incidence was conducted in 1989 by the CAU in response to the concern of the citizens from Tewksbury. The results of these investigations are summarized later in this public health assessment addendum.


Health-related concerns were expressed to environmental officials during the comment period for the selection of the landfill remedial plan. Legislators on the federal and state level as well as local government and health officials were concerned about the possibility of Tewksbury municipal well contamination by hazardous compounds migrating from the landfill. Concern was also expressed that contaminants would flow downstream from Content Brook to the Shawseen River which serves as a municipal water source for other neighboring towns. It was reported that children have been observed playing in ponds near Content Brook and Gray Street. It is believed by local citizens that by such activity, these children may be at risk of hazardous exposure to landfill contaminants. Private wells are reported to exist at residences near the landfill (1). Citizens living at these residences on Gray Street are concerned about future migration of landfill contaminants to these wells.

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