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Hazardous Waste Cleanup: Allegro Microsystems Incorporated in Willow Grove, Pennsylvania

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    Cleanup Status

    From 2003 to 2005, and under the supervision of the Pennsylvania Department of Environmental Protection (PADEP), Allegro completed the investigation and remediation of the property in accordance with the PADEP Land Recycling and Environmental Remediation Standards Act (Act 2).  The Pennsylvania Statewide Health Standards (SHS), which are equivalent to the EPA residential standards and deemed protective of public heath, were applied to the investigation and remediation. 

    The investigation evaluated six areas of concern (AOCs) at the Facility that potentially posed an environmental concern.  The six AOCs comprised of four solid waste management units (SWMUs), one aboveground storage tank (AST) and one underground storage tank (UST).  PADEP oversaw and certified the closures of the SWMUs, AST and UST in 2003.

    In addition to the closure of the aforementioned units, a site characterization was conducted to determine the potential environmental impacts within, or immediately adjacent to the property that may resulted from past operations.  The site characterization consisted of a site-wide groundwater monitoring and surface and subsurface soil samples for the constituents of concerns (COCs) that consisted of heavy metals, polycyclic aromatic hydrocarbons (PAHs), and volatile organic compounds (VOCs).  The investigation concluded that the soil results for the COCs were below the SHS and do not pose an unacceptable risk to human health.  Furthermore and with the exception of the element barium, groundwater results for the COCs were also below the SHS. 

    Allegro never used barium or its related compounds in any of their industrial processes. However, barium was detected at varies levels throughout the property.  Barium exceedances above the SHS of 2000 mg/L were detected in five of the twenty-four monitoring wells and twelve temporary well points.  The exceedances range from 2,400 mg/L to 7,000 mg/L. The barium exceedances in groundwater are localized in the shallow aquifer and are confined within a one acre area located in the southeastern quadrant of the Facility.  Groundwater flow in this area of the Facility discharges to the unnamed tributary.  In utilizing a mass-balance water quality analysis model (PENTOXSD model) to evaluate diffuse groundwater discharge to surface water, PADEP determined that the barium levels in groundwater do not adversely impact the unnamed tributary.  The investigation did not identify any potential sources for the barium in groundwater.  Therefore, PADEP concluded that the barium detections in groundwater are naturally occurring in nature. 
    The former Facility has since been redeveloped into a shopping center that includes a Walmart Supercenter and several big box retailers.  The property is zoned for non-residential use and will remain non-residential for the foreseeable future.  A deed restriction on the property prohibits the use of onsite groundwater for any purposes and therefore, prevents direct human exposures to barium.  Historic groundwater results confirm that the elevated barium levels in groundwater are stabilized within the one acre area.  The barium levels in groundwater do not adversely impact the surrounding environment. 

    Based the above assessment, EPA has proposed no further corrective action or land use controls are necessary at this time at the Facility.  EPA has determined that its proposed decision is protective of human health and the environment. 

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    Site Description

    Interactive map of Allegro Microsystems Incorporated, Willow Grove, PA

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    The former Allegro facility occupied approximately 30 acres located in Willow Grove, Pennsylvania.  Much of the former property (approximately 60%) was open landscape and asphalt-paved areas that included parking lots and access roadways.  Approximately 40% of the former property was used for manufacturing and product distribution.  The operations structures consisted of a large single-story building, a pump house, the wastewater treatment plant (WWTP) and a small stone shed.

    From 1990 to 2001, Allegro manufactured large-scale integrated circuits used in various applications such as automobile ABS systems, smoke detectors, computer memories, space and telecommunications hardware, oil exploration, and battery operated devices.  The circuits were processed on the surfaces of polished silicon wafers.  The wafers were mass-produced using photolithography techniques, high temperature heat treatments, and chemical etching.

    In October 2001, Allegro discontinued operations and commenced decommissioning of the facility.  In September 2002, Allegro sold the property to a commercial developer who redeveloped the former facility into its current usage as a shopping center that includes a Walmart Supercenter and several big box retailers.

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    Contaminants at this Facility

    While barium was detected at varies levels throughout the property PADEP concluded that the barium detections in groundwater are naturally occurring in nature.  There were no other contaminants of concern.  

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    Institutional and Engineering Controls at this Facility

      Institutional Controls were not required at the facility.

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      Land Reuse Information at this Facility

      The site is being reused.

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      Site Responsibility at this Facility

      Resource Conservation and Recovery Act (RCRA) Corrective Action activities at this facility have been conducted under the direction of EPA Region 3.

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