The Nuclear Metals, Inc. (NMI) Superfund Site (the Site) is located at 2229 Main Street and comprises approximately 46 acres of land in Concord, Middlesex County, Massachusetts. The property includes a sphagnum bog, a cooling water recharge pond, a former landfill and a holding basin. The Site is surrounded by residential and woodland areas to the east and south, light commercial and industrial areas to the west, and Main Street (Route 62) and the Assabet River to the north.

• Studies of the causes of brittleness in beryllium;
• Determination of the original phase diagrams for alloys of uranium, beryllium, zirconium, hafnium, tungsten, and other special metals;
• Alloying of uranium for specific properties, including corrosion resistance and high stress/rupture characteristics. Similar studies to achieve higher strength in beryllium;
• Development of unique techniques for testing and evaluating fuel elements and fuel element materials;
• Development of high-strength zirconium alloys for use as cladding on fuel elements;
• Electroplating studies;
• Basic studies of corrosion in zirconium and uranium alloys. Oxidation mechanism for zirconium;
• Effects of liquid metal environments on zirconium and uranium alloys;
• Development of cermets (ceramic-metallic compounds), including beryllium-beryllium oxide and stainless steel-uranium oxide;
• Development of original methods of chemical analysis for various constituents in beryllium, uranium, and zirconium alloys;
• Oxidation studies of graphite, platinum, and refractory metals;
• Development and fabrication of inter-metallic compounds of uranium;
• Development of melting and casting techniques for beryllium and uranium alloys;
• Development of machining methods for uranium, thorium, beryllium, yttrium, and other metals;
• Technical and economic evaluation of proposed reactor fuel types and fabrication procedures;
• Production of fuel elements for use in submarine reactors;
• Production of fuel elements for several different reactors at National Laboratories;
• Development of methods of extrusion and drawing of seamless molybdenum tubing and molybdenum tubing clad inside and out with other metals such as stainless steel;
• Development of extrusion methods for niobium and tantalum; and

The focus of site operations shifted from research and development to large-scale production in the mid-1970s. In September 1972, NMI employees purchased the operation. Since 1972, NMI and related entities have owned and operated the Site. Operations ceased in Nov 2011. After the 1972 purchase, NMI developed a large-scale depleted uranium (DU) manufacturing operation, which included, but was not limited to, the manufacturing of penetrators, or bullets, from DU as a defense contractor for the United States (US) Army. Building D was constructed in 1978 to expand the production capabilities of the facility. Building E was constructed in 1983 and was used to house the radioactive waste processing operations. A Holding Basin that was used for discharging liquid waste is located at the northeast corner of Building E.

Other work included manufacture of depleted uranium (DU) shields and counter weights, manufacture of metal powders, beryllium and beryllium alloy parts production, and manufacture of specialty titanium parts. 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. On May 12, 2003, the Massachusetts Department of Public Health – Radiation Control Program (MADPH-RCP) modified Starmet’s radioactive materials license for manufacturing or operations to allow only their possession on-site. Starmet officially vacated the property on November 2, 2011. The Radioactive Materials License was terminated by the MADPH-RCP on November 8, 2011.

The following summary of the DU and powder manufacturing process presents an overview of the types of activities that occurred within the buildings:

• General DU Operations – Raw DU material was received at the Site as derbies or as cut pieces and was cast and/or machined into products in the facilities. The casting process was conducted under vacuum. The melt was poured into one or more molds and allowed to solidify, possibly assisted by an inert gas back fill. At that point, the casting may have been considered a completed object as is, or may have been further processed, such as by heat treating, CNC machining, enhancing the surface finish by hand operations such as filing or grinding within vented enclosures, and/or by painting or electroplating.
• Penetrator Production – DU penetrator production was a multi-step process. It began with a DU melt consisting of DU and titanium. The metal was melted under vacuum in a zirconium coated graphite crucible. The coating prevented reaction between the molten uranium and graphite. Following a hold at 1400o C to uniformly distribute the titanium in the alloy, the melt was poured into yttrium-coated molds to form ingots.
• Billets Production – The ingots were slipped into lengths of copper tube blocked at one end. A copper end plate, equipped with an evacuation tube, was welded onto the open end. The evacuation tube was then connected to a vacuum system and each billet assembly was evacuated. The evacuation tube was then crimp-sealed to form a leak-tight assembly (billet). Billets were then extruded. Extrusions were performed in a 1400-ton extrusion press. Billets were loaded into ovens and maintained at 600o C for one-hour minimum prior to extrusion. The die was lubricated and the billets were pushed through the die at a constant ram speed. Immediately upon exiting the extrusion press, each rod was automatically transferred to a forced air/water mist cooling bed. Rod stock exiting this system was cool to the touch. The copper sheath on the extruded bars was then removed by acid digestion (pickling). After removal of the copper sheath, extruded rods were straightened using a Sutton two-roll straightener to facilitate subsequent cutting operations. The rod stock was cut into blanks of appropriate length by sawing.
• Finish Machining – Finish machining required a precision pre-machined blank with a uniform diameter and flat ends perpendicular to the bar axis. These requirements were met by centerless grinding to the desired finished diameter. The ends were faced flat and perpendicular to the bar axis. DU penetrator blanks were turned to their final configuration on computer numerical control (CNC) lathes. The Starmet Parties occupied the facility from October 1, 1997 until November 2, 2011 and conducted small-scale operations within a portion of the buildings as follows:
  • Powder Manufacture – Metals were converted to powder by the rotating electrode process (REP) equipment. A bar of metal was rotated in a helium-filled chamber where it was melted by an electric arc. As the metal liquefied, it spun off and solidified into a powder. Metals used include aluminum, steel, titanium, and nickel base super alloys. These powders were used in the photocopier industry, electronic component cleaning mediums, and in the manufacture of surgical implants.
  • Beralcast ® Manufacture – Advanced metal products for government, aerospace and commercial applications were made using Starmet’s patented Beralcast alloy and related patented and proprietary technology. Starmet’s Beralcast is a beryllium-aluminum alloy that can be produced in near net and net shape cast forms. These products were produced by a variety of techniques, including investment and permanent mold casting techniques.

Given the type of work performed and the quantity of production over time conducted within the buildings, widespread uranium contamination was found in the manufacturing areas. The metallurgical processes created uranium oxide dust that accumulated in cracks and crevices and other horizontal surfaces within the buildings. The volume of material used and the numerous years of operation resulted in the significant uranium contamination of the production buildings.

Radiological contamination within the buildings was primarily uranium. Uranium is a mixture of three uranium isotopes: U-234; U-235; and U-238. The ratio of these isotopes varies, depending on the processing (enrichment) of the uranium. The four basic categories of enrichment are natural uranium, low enriched uranium (LEU), high enriched uranium (HEU), and DU. All four categories of uranium were processed at the facility over the course of its history. LEU and HEU were processed along with DU during the early years of operations. DU was the primary type used from the mid-1970s on. In addition, thorium was also processed at the Site for research and development of reactor components and as thoriated-tungsten. Thorium was used in smaller amounts than uranium and was determined to be a minor component of contamination within the buildings.

As configured prior to the Building NTCRA, the Site had five interconnected buildings with several smaller outbuildings, e.g., butler buildings, well houses, storage sheds, etc. Each of these buildings is described below in more detail. Most buildings had been vacant for some time and were in disrepair.

In January 2006, and in support of the EE/CA (de maximis 2008), de maximis completed a building survey. This survey included performing a health and safety survey, and a contamination assessment to evaluate the levels of radiological contamination and exposure rates. The survey also assessed the presence of chemicals within the buildings. The criterion of 40 dpm/100 cm2 (10 mrem/year Total Expose Dose Equivalent (TEDE) was utilized to evaluate unacceptable risk associated with radionuclides within the site structures.

Building A

Building A was constructed in 1958, and was one of the original three facility buildings. The building was 216-feet by 80-feet with two floors. The building consisted of office space as well as production and research space. The building was designed with laboratories for metallography, applied physics, analytical chemistry, physical metallurgy, and chemical metallurgy, as well as shops for glass production and machine work. According to Starmet personnel, during the period of high-volume production of DU-penetrators, office spaces within Building A were converted to use for quality inspection and other industrial uses. Later, these areas were converted back to office spaces (Starmet, 2006). A roof evaluation found a variety of leaks in the Building A roof, and one area of deteriorated roof decking (Emanuel Engineering, 2004).

Building B

Building B was constructed in 1958 and was one of the original three facility buildings. It was a 97-feet by 60-feet, two-story building that housed boilers and services for the plant. Other portions of the building were used for a medical clinic, lunch / conference room, and locker rooms. The boiler room reportedly contained a sump that periodically discharged into the Cooling Water Recharge Pond. In 1990, approximately five gallons of No. 6 fuel oil were released to this sump (Tetra Tech NUS, Inc, (Tetra Tech) and Dynamic Corporation, 2000) (GZA Environmental, Inc, 1998). A roof evaluation found a variety of leaks in the Building B roof, and one area of deteriorated roof decking.

Building C

Building C was constructed in 1958 as a production building and was one of the original three facility buildings. The building was 200-feet by 130-feet and two stories high. The majority of the building was utilized as production space that was open from floor slab to roof. A small portion contained a second floor mezzanine. This area was also used for storage of DU penetrators. Building C was the main production center for the facility from 1958 until construction of Building D in 1978. Building C contained the foundry, fabrication shop, machine shop, carpentry shop, and welding area, as well as the shipping and receiving area. DU extrusion activities also took place in Building C. The fabrication shop also originally included a pickling tank and a caustic tank.

A concrete pit was located beneath the 1,400-ton extrusion press. This pit contained an estimated 10,000 gallons of water resulting from infiltration through roof leaks. Most of Building C was designated as a Radiation Work Area based on past production activities and measurable levels of contamination. A roof evaluation found a variety of leaks in the Building C roof and one area of deteriorated roof decking. When water leaked through the roof, it came into contact with lighting and other electrical equipment within Building C.

Building D

Building D, constructed in 1978, was a 280-feet by 160-feet, two-story production building. A small portion of Building D contained office space. Building D was constructed to augment the production capacity of Building C. It consisted of a fabrication area (including uranium fabrication), computerized milling machines, a quality control section and an acid pickling area (United States Nuclear Regulatory Commission (NRC), 1997). Buildings C and D were separated by fire walls. A centerless grinder milling machine was also present and contained dried DU powder/sludge.

Building E

Building E was constructed in 1983 and occupied in January 1984 for the purpose of housing the radioactive waste processing operations, including a concrete plant and an emergency generator and associated 250-gallon fuel tank (United States Nuclear Regulatory Commission (NRC), 1997). Building E contained two 2,000-gallon tanks for holding sulfuric acid (5 percent (%) solution), as well as two 55-gallon sulfuric acid (93% solution) day tanks (Oak Ridge National Laboratories (ORNL), 1997). The building also contained locker rooms and bathroom facilities. The footprint of the building had a main section of 200-feet by 150-feet, with a smaller 120-feet by 70-feet section on the south side. When sludge discharge to the Holding Basin was discontinued in 1985, wastewater was routed back to an evaporator (called the “Sonodyne”) in Building E from the Holding Basin Tank House. Building E was constructed over an area originally used for materials and waste storage. A storage building (Building B3), used for DU waste processing, and a flammable liquids shed were moved before Building E was constructed. During the clearing of the area for Building E, underground pipes, manholes, and catch basins, some up to 20-feet deep, were removed.

Building E also contained a former research and development area, known as the Hydrofluoric Acid Area, and above ground storage tanks that contain used machining coolant presumed to be DU contaminated. The Starmet Parties operated the Sonodyne machine located in Building E to treat wash water as well as rain water that entered the building. The loading/receiving area was used to store beryllium waste prior to off-site shipment.

Butler Buildings

There were four pre-engineered, insulated, metal buildings used for various support purposes on the Site. Referenced as the “Butler Buildings” and numbered B1, B2, B3, and B4, they occupied footprints of 2,048, 2,048, 2,400, and 4,800 square feet, respectively. These structures were all slab on grade and included: •

• Butler B1: Building B1 was a metal “Butler” building that was part of the original Site constructed in 1958. Building B1 was historically used for storage, as well as shipping and receiving. An environmental assessment completed in 1997 by Oak Ridge National Laboratory, under contract to the NRC, indicated that Building B1 was used for DU storage. Butler B1 was also used as a fabrication/maintenance shop.
• Butler B2: Building B2 was a metal “Butler” building that was part of the original Site constructed in 1958. It was historically used for storage, as well as shipping and receiving. The 1997 ORNL assessment indicated that Building B2 was also used for DU storage. 
• Butler B3: Building B3 was a metal “Butler” building originally built in 1976. It was constructed as a separate waste handling facility. DU wastes were processed for disposal both inside and outside of the building. It was removed from its original location in 1983 for the construction of Building E. The metal walls were washed and painted and the building was relocated to a position just east of Building C. It was used to store uranium-contaminated equipment received in the middle to late 1980s from American Lead, a former manufacturer of DU penetrators located in Colonie, New York (Starmet, 2006).
• Butler B4: Building B4 was constructed in 1977 as a loading dock area. Most of Building B4 was used as a stock room. The 1997 ORNL assessment stated that approximately 200-gallons of 93% sulfuric acid (four drums) had been staged in Building B4. More recently, Butler B4 was used to store Site personnel lab coats and Beralcast molds, and where the Beralcast molds were produced. The area where the Beralcast molds were produced was a respiratory protection area due to the silica products that were used during production.
•  

Tank House

The tank house was constructed in 1958 to serve as the collection, distribution, and treatment point for radioactive liquid acid wastes generated during the handling and production of DU stock and other specialty metals. The tank house was a 1,200 square foot, two-level, wooden framed structure built on a concrete slab located adjacent to the Holding Basin. Liquid wastes flowed to the tank house, were neutralized though the addition of lime, and then discharged to the Holding Basin. The structure is comprised of an upper (ground surface) level and lower (below ground surface) level. The upper level was used for storage of the neutralizing agents, e.g., lime, soda ash, with the lower level occupied by two 4,000-gallon above ground storage tanks. Recent use of the storage tanks was to store wash water prior to it being treated by the Sonodyne. Radiologically contaminated sludge was present in the bottom of each tank.

Hydrogen Peroxide Tank House

Located northeast of Butler Building B3, the Hydrogen Peroxide Tank House was a 15- foot by 12-foot wooden framed structure constructed within a 6-inch thick, six-foot high, concrete secondary containment structure. This building housed a 5,000-gallon lined above ground storage tank that was used to store 49% hydrogen peroxide (H2O2) (stabilized). The hydrogen peroxide was used in two processes: as an oxidizer in water treatment prior to neutralization/evaporation; and as an oxidizer for the closed loop pickling (where copper-clad DU bars were pickled chemically to remove the copper from the uranium). This structure was reported to have been built around the time Building E (1983) was constructed (Starmet, 2006).

Underground Storage Tank Area

Fuel oil for the Site was stored and dispensed from two 10,000-gallon underground storage tanks (USTs) located in the courtyard area between Buildings A and C, to the north of Building B. The fuel oil was used in the facility boilers that were located in Building B. A tank integrity test provided in a previous environmental study from the late 1990s identifies the product as No. 4 fuel oil. A review of on-site records, conducted by de maximis in March 2004, did not indicate the presence of other USTs on the Site.

Miscellaneous Structures

Miscellaneous structures at the Site include: • Gas Cylinder Storage Sheds:

• Two gas cylinder storage sheds, installed in 1983 to 1984 (Starmet, 2006), were located directly south of Butler Building B2. A six-foot high chain-link fence surrounded the sheds. The sheds, measured 8-feet by 20-feet, were constructed of fabricated steel “sealand” containers with ventilation openings throughout the exterior walls. The sheds were used to store cylinders of nitrogen and argon. Laboratory-grade acids (e.g., hydrochloric and sulfuric acids) also were stored in the sheds.
• Acetone Distillation Shed (Shed D2): Located outside of Building D (adjacent to Room D-116) was a 10-foot by 10-foot wooden framed structure constructed around 1978, which housed an acetone distillation unit. The roof was constructed of a wooden frame covered by asphalt shingles. 
• B-1-2 Shed: This structure was located between the B1 and B2 buildings. The shed contained leaf blowers, lawn mowers, weed trimmers, and other lawn maintenance equipment. It also contained a small volume of gasoline and oils.
• Wooden Sheds: In addition to the shed structures identified above, there were also two small wooden shed structures: (1) one located outside Building C (approximately 125 feet northeast of the hydrogen peroxide tank); and (2) Shed D1, located on the eastern side of Building D. The sheds were constructed of wooden walls and roof supports with asphalt shingled roofs. The shed outside Building C housed fire suppression equipment, such as hoses, nozzles, and a fire hydrant. Shed D1 is a 15-feet x 12-feet wooden structure with an asphalt shingle roof, which was originally used to protect the overhead exterior door at this location.

Pursuant to Section 105 of CERCLA, 42 U.S.C. § 9605, USEPA placed the Site on the National Priorities List (NPL), set forth at 40 C.F.R. Part 300, Appendix B, by publication in the Federal Register on June 14, 2001, 66 Fed. Reg. 32235, 32241. From April 2002 to April 2003, USEPA performed two Time-Critical Removal Actions (TCRAs) at the Site that included, among other things, the installation of a temporary cover over the holding basin and the installation of a temporary cap over the small landfill.

On June 13, 2003, USEPA and certain potentially responsible parties (the Settling Federal Agencies and the Respondents) entered into an Administrative Order by Consent for Remedial Investigation/Feasibility Study (RI/FS) (U.S. EPA Docket No. CERCLA 01-2003-0021) for the Site, which was amended on February 13, 2008 and October 9, 2012 (jointly referred to herein as the Administrative Order by Consent (AOC) for RI/FS). On June 13, 2003, the Respondents initiated RI/FS work. The RI/FS AOC required the Respondents to perform one or more Engineering Evaluations / Cost Analysis (EE/CAs), if requested to do so by USEPA.

In 2004, the Massachusetts Department of Environmental Protection (MassDEP) and the United States Army (Army) entered into an agreement whereby the Army financed the removal of approximately 3,800 drums of depleted uranium and other waste materials that were stored at the Site. MassDEP performed this drum removal from September 2005 to March 2007.

On June 26, 2007, a small fire occurred at the Site. Following the fire, the Concord Fire Department (CFD) requested that USEPA remove hazardous materials present inside the buildings that posed a fire safety threat. From January 7, 2008 to September 24, 2008, USEPA performed a third TCRA at the Site to remove hazardous substances from inside the buildings that posed a threat of fire or explosion. The Concord Fire Department also requested that a Fire Hazards Analysis and Fire Protection & Life Safety Assessment (FHA) be performed to provide a comprehensive evaluation of the fire risks posed by the buildings, their contents, and to assess the appropriate levels of fire protection and life safety once the facility is vacated by the Starmet Parties. USEPA requested Respondents perform this evaluation, which was completed in August 2009 (Hughes Associates, 2009).

Beginning with USEPA’s Approval Memorandum in December 2007 for the EE/CA, work was implemented by the Respondents. 

In December 2007, USEPA signed an Approval Memorandum for performance of an EE/CA to evaluate various alternatives to address the buildings located on-site and their contents. The Respondents performed the EE/CA. USEPA issued the completed EE/CA in February 2008. In April 2008, USEPA issued a fact sheet providing notice of the completion of the EE/CA and USEPA’s proposed NTCRA to address the deteriorating, contaminated buildings. USEPA provided an opportunity to the public to comment on the proposed NTCRA. On September 23, 2008, USEPA issued an Action Memorandum that authorized the performance of a NTCRA at the Site to demolish the buildings. The Administrative Order on Consent, pursuant to which the NTCRA was performed, became effective on August 9, 2011.

USEPA, the Respondents, and Settling Federal Agencies (SFAs) entered into an Administrative Settlement Agreement and Order on Consent (AOC) for the Building NTCRA that became effective on August 9, 2011. Starmet officially vacated the property on November 2, 2011.  The Radioactive Materials License was terminated by the MADPH-RCP on November 8, 2011.  Building Demolition was completed in August 2016. A final report for the Building NTCRA was approved by EPA on June 28, 2017. In that approval, USEPA determined that all Building NTCRA work had been fully performed in accordance with the Building NTCRA AOC, except for continuing obligations that include: Post-Removal Site Control (PRSC), payment of Future Response Costs, and record retention.  PRSC is being performed pursuant to a PRSC Plan approved on May 31, 2017. 

The Remedial Investigation (RI) was completed in April 2014 and the Feasibility Study (FS) was completed in November 2014.  EPA published notice of the completion of the FS and the Proposed Plan outlining EPA’s preferred remedial action alternative on October 31, 2014.  USEPA’s Record of Decision (ROD) was issued on September 28, 2015 and requires remedial measures including: excavation and off-site disposal of approximately 82,500 cubic yards of contaminated materials, stabilization and capping of materials within the “Holding Basin” area of the site, in-situ and ex-situ treatment of contaminated groundwater.  The ROD also included an Action Memorandum to accelerate a portion of the groundwater cleanup, targeting VOCs and 1,4-dioxane on the Downgradient Properties, to be performed as a second NTCRA while negotiations proceeded for implementation of the full remedy. 

Additional delineation of the extent of the 1,4-dioxane and VOC plumes in the downgradient area was performed from September – December 2015 under the RI/FS AOC, between issuance of the ROD and the effective date of the Groundwater NTCRA AOC.  This work included groundwater profiling, monitoring well installations, groundwater quality and water level monitoring, and hydraulic conductivity testing.  To delineate the area of hydraulic influence for Municipal Wells Assabet 1A and 2A, a shutdown and restart test of these wells was performed in March 2016.   

USEPA, Respondents, and SFAs entered into an AOC for Groundwater NTCRA that became effective on July 11, 2016.   Work under the Groundwater NTCRA has included performance of an aquifer pump test, installation and operation of a temporary treatment system, completion of treatability testing for a permanent treatment system, and design and construction of the final treatment system.  At lodging of the Consent Decree, remaining work under the NTCRA for Groundwater will be completed as part of the RD/RA.