The Nuclear Metals, Inc. (NMI) property is located on a 46.4-acre parcel located at 2229 Main Street in Concord, Middlesex County, Massachusetts. The facility includes five interconnected buildings, a paved parking area, a sphagnum bog, a cooling water recharge pond, and a holding basin. The topography of the property slopes down to the north. The property is bordered to the north by Main Street, commercial and residential properties, and the Assabet River; to the east by woodland and residential properties; to the west by woodland and commercial/industrial properties; and to the south by woodland and residential properties.
In 1958, NMI began operating a manufacturing facility on previously undeveloped land. Nuclear Metals, Inc. produced depleted uranium (DU) products, primarily as penetrators for armor piercing ammunition. They also manufactured metal powders for medical applications, photocopiers, and speciality metal products, such as beryllium tubing used in the aerospace industry. From 1958 to 1985, NMI discharged wastes to an unlined holding basin. Cast depleted uranium ingots or billets were jacketed in copper, which were heated and extruded into long rod stock. The extruded depleted uranium rod had a resulting thin layer of copper coating, which was removed in a nitric acid pickling operation. During the pickling process, “small quantities” of copper and uranium were dissolved in the nitric acid. The spent nitric acid solution was collected, neutralized with a lime slurry, and then discharged to the unlined, in-ground holding basin. The discharge to the holding basin ceased in 1985 when NMI began using an acid closed-loop recycling process.
NMI handled natural and depleted uranium, thorium and thorium oxide originally under license to the Nuclear Regulatory Commission (NRC) but later (from 1997 to 2011) under the Massachusetts Department of Public Health Radiation Control Program (MADPH-RCP). In addition to radioactive materials, NMI handled other hazardous substances such as: sulfuric and nitric acids for process activities; trichloroethene (TCE), tetrachloroethene (PCE), and 1,1,1-trichloroethane (TCA) as solvents (1,4 dioxane also used in process as a stabilizer for TCA); zirconium; magnesium; beryllium; acetone; hydrogen peroxide; flammable gases (propane and acetylene); and Poly Chlorinated Bi-phenyls (PCBs). Operation and maintenance of the facility required the use of cutting oils for milling operations, hydraulic oils for operation of heavy presses, industrial cleaners and degreasers, air filters, and fuel oil for winter heating. In addition, the facility had on-site electrical transformers.
On October 1, 1997, NMI was renamed Starmet Corporation. Starmet, its subsidiaries, affiliates, and related entities (collectively, the Starmet Parties) continued to perform small scale operations at the Site through October 2011. Starmet officially vacated the property on November 2, 2011. The Radioactive Materials License was terminated by the MADPH-RCP on November 8, 2011.
In October 2014, EPA proposed a final remedy for the cleanup of soil, sediment and groundwater contamination at the site which generally includes:
- Excavation and off-site disposal of approximately 82,500 cubic yards of contaminated sediments, and non-Holding Basin soils located throughout the site;
- In-Situ stablization of DU contaminated soils in the Holding Basin using Apatite II injection, encapsulation of the Holding Basin using a vertical barrier wall and sub-grade cover, and filling the Holding Basin with clean soil to grade;
- Ex-situ treatment of VOCs and 1,4 dioxane in overburden and bedrock groundwater;
- In-Situ treatment of DU and natural uranium in overburden and bedrock groundwater, respectively, using Apatite and/or Zero-Valent Iron; and
- Long-term monitoring of groundwater and institutional controls to 1) restrict excavations in the Holding Basin Area; 2) prohibit use of contaminated groundwater until cleanup levels are met; and 3) require evaluation of vapor intrusion risks and, if necessary, installation of vapor mitigation systems should future structures be built above the VOC plume before cleanup levels are met.
The proposed plan was described in fuller detail at a public information session on November 12 at 6:30 pm and oral comments can be made on the proposed plan at the public hearing on December 10 at 6:30 pm at Concord Town Hall at 22 Monument Square in Concord, MA. Written comments can be made during the public comment period for the proposed plan which began on November 13, 2014 and will end at midnight on January 14, 2015. The Proposed Plan can be found at:http://www.epa.gov/region1/superfund/sites/nmi/568091.pdf