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The Nyanza Chemical Waste Dump site is a 35-acre area next to an active industrial complex in Ashland, Massachusetts. From 1917 to 1978, facilities produced textile dyes, intermediates and other products on site. Nyanza Inc. operated on site from 1965 until 1978. Large volumes of industrial wastewater containing high levels of acids and numerous organic and inorganic chemicals, including mercury, were generated by these facilities, leading to soil and groundwater contamination. Over 45,000 tons of chemical sludges generated by Nyanza's wastewater treatment processes, along with spent solvents and other chemical wastes, were buried on site. The area that contained the largest amount of buried waste and exposed sludge is referred to as the Hill section. The current owner leases the old plant grounds to various businesses.

The site was added to EPA's National Priority List on December 30, 1982.

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What Has Been Done to Clean Up the Site?

The site is being addressed through federal and state actions.

The site is being addressed in five stages: initial actions and four long-term remedial phases focused on source control and cleanup of the soil, off-site groundwater, wetlands and the Sudbury River.

Source Control: EPA's source control remedy included excavating all outlying sludge deposits and contaminated soils and sediments associated with these deposits; consolidating this material with the on-site Hill sludge deposits; capping the Hill section to prevent water from entering it and spreading contaminants; putting in a groundwater and surface water diversion system on the upgradient side of the Hill area; backfilling excavated areas to original grade; fencing the site; establishing a vegetative cover in the wetland areas; and expanding groundwater monitoring. Cleanup actions took place between 1990 and 1992.

Off-Site Groundwater: EPA selected an interim remedy to clean up off-site groundwater contamination in 1991. The selected remedy was to pump and treat the contaminated groundwater from the most contaminated portions of the plume for five years. However, due to the discovery of additional contamination, EPA reevaluated the remedy. After additional data collection and risk assessment, with added emphasis on potential indoor air contamination, EPA updated the remedy in 2006. It includes the extraction of dense non-aqueous phase liquid (DNAPL) from the groundwater plume as well as the installation of vapor mitigation systems in homes overlying the contaminated plume. Forty systems were installed in 2007. The Massachusetts Department of Environmental Protection (MassDEP) inspects these systems annually. EPA also conducted subsurface investigations to locate pockets of recoverable DNAPL and installed two extraction systems to recover the residual DNAPL, which is contributing to dissolved VOC contaminants in the downgradient plume. EPA presented a Proposed Plan for Operable Unit 02 to the public for review in January 2020, and held a public comment period through March 20, 2020. EPA is preparing a ROD for Operable Unit 02 to implement a final groundwater cleanup remedy.

Wetlands: The remedy for contaminated sediment and surface water of the adjacent eastern wetlands and drainageways between the site and the Sudbury River included excavation of the contaminated material and its placement in the on-site landfill. Mercury-contaminated sediments were excavated from four areas (Eastern Wetland, Trolley Brook, Outfall Creek, Lower Raceway) and disposed of in the on-site landfill. EPA completed all cleanup activities between 1999 and 2001.

Sudbury River: The remedy includes periodic fish tissue sampling to evaluate mercury concentrations, and institutional controls such as the posting and maintenance of fish consumption advisory signs in accessible areas along the Sudbury River in six communities..

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What Is the Current Site Status?

MassDEP iconducts operation and maintenance activities for remedies implemented at the Site. The excavation of contaminated soil and capping of the Hill area of the site has reduced the potential of exposure to hazardous substances by controlling contaminant migration and isolating wastes. Wetland excavations and restoration have eliminated the ongoing mercury contamination source to the Sudbury River. In 2007, EPA installed 41 vapor mitigation systems to control the risk of vapor intrusion in structures located above the shallow groundawter plume, where the migration of VOC vapors is most likely to occur. In 2013, EPA installed two pilot DNAPL extraction systems in former manufacturing source areas of the Site. EPA has posted advisorysigns along the Sudbury River warning against the consumption of mercury-contaminated fish. These actions have reduced and/or mitigated risk from Site contamination. EPA is preparing a ROD for a final groundwater remedy to reduce residual contamination which is resulting in a groundwater plume emanating from the Site.


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Activity and Use Limitations

At this site, activity and use limitations that EPA calls institutional controls are in place. Institutional controls play an important role in site remedies because they reduce exposure to contamination by limiting land or resource use. They also guide human behavior. For instance, zoning restrictions prevent land uses – such as residential uses – that are not consistent with the level of cleanup.

For more background, see Institutional Controls.

Institutional controls are required for this site.

This site requires ICs because a decision document, such as a Record of Decision, has documented some level of contamination and/or remedy component at the site that would restrict use of the site. These ICs are required to help ensure the site is used in an appropriate way and that activities at the site do not damage the cleanup components. These ICs will remain in place for as long as the contamination and/or cleanup components stay on site. The site contacts should be consulted if there are questions on the ICs for this site.

The following IC Instruments provide media-specific use restrictions that have been implemented by EPA for protecting human health, the environment and remedial engineering on this site. Instruments are documents used by EPA or other organizations to implement the use restrictions at a site. To know about other media-specific use restrictions that are planned but not implemented at this site, please contact the Regional Office using the Site Contact listed above.

Click here for IC Instruments implemented for this site.

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