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New Hampshire Department of Environmental Services

Site Summaries

Mohawk Tannery Site
Contact: Robin Mongeon (603) 271-7378

The former Mohawk Tannery site, also called Granite State Leathers, encompasses approximately 30 acres on the Nashua River in Nashua. The tannery operation occupied about 15 of the 30 acres and produced tanned hides for leather between 1924 and 1984. It has been inactive since then.

While in operation, the tannery generated both alkaline and acid waste streams from its hide preparation and tanning processes. Little is known about the tannery waste treatment and management practices prior to the 1960s. From the 1960s until the completion of an on-site treatment facility in 1981, the acid waste stream passed through a series of five settling basins and was then discharged to the Nashua River via an open channel. The alkaline waste stream was conveyed to a screen building for removal of solids, and then to two impoundment lagoons, located within the river’s 100-year floodplain. After settling, the liquid fraction of the alkaline waste stream was discharged directly to the Nashua River, and sludge was periodically dredged from the lagoons and disposed of on-site in several unlined landfills.

An estimated 60,000 cubic yards of sludge remains in the lagoons and unlined landfills and continues to present a potential threat to groundwater and the Nashua River. These disposal areas were not designed, constructed, or maintained in accordance modern standards, and therefore the possibility of a catastrophic washout during a flood remains an ongoing concern. The site was proposed for the National Priorities List (NPL) on the basis of these past disposal practices. The site has not been added to the NPL.

US Environmental Protection Agency (EPA) completed a time-critical removal of 55 drums of hazardous materials and asbestos-containing material from the former tannery building in January 2001. An engineering evaluation/cost analysis (EE/CA) was completed in July 2002, and a remedial investigation was completed in June 2005. These studies provided a basis for the development and evaluation of potential cleanup options.

The New Hampshire Department of Environmental Services (DES), the EPA, and the city of Nashua continue to review options for this site. During 2009 the EPA conducted pilot tests to determine whether the site can be stabilized in place using a solidification stabilization process. Such an approach would be less expansive than excavating and hauling the material to a suitable disposal site, while still allowing the site to be suitable for certain types of reuse.

In 2012 the City of Nashua demolished the dilapidated main tannery buildings, which had become a public safety concern. In 2012 DES and EPA initiated a study of the southern parcel to determine if all or a portion of the parcel met cleanup criteria and would not present a risk to human health or the environment. The southern parcel screening level human health and ecological risk assessment was completed in late 2013. The results indicate that groundwater exceeds drinking water standards, asbestos was detected in several samples on the parcel, a potential risk to terrestrial receptors may exist in two wetland areas associated with cadmium, chromium and dioxin. There was no significant risk to aquatic organisms associated with groundwater discharging to surface water or river sediments and there was not significant risk to recreational users associated with wetland soil/sediment or riverbank soils or river sediments.

A local developer is exploring the option of acquiring the site and completing remedial actions at the site, followed by site development. The State and EPA have had numerous discussions with the developer regarding cleanup strategies at the site.

NH Department of Environmental Services | 29 Hazen Drive | PO Box 95 | Concord, NH 03302-0095
(603) 271-3503 | TDD Access: Relay NH 1-800-735-2964 | Hours: M-F, 8am-4pm

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