1.0 Site Identification
|Type of Site:
||Complex Decommissioning Site
||Maryland Heights, MO
2.0 Site Status Summary
Sigma-Aldrich Company's (SAC) Fort Mims facility is located in Maryland Heights, Missouri. The site was originally owned by Pathfinder Laboratories and was sold to Sigma Chemical Company (SCC) in 1987. In 2002, SCC changed its name to SAC. Radioactive materials have been used at the Fort Mims facility since 1975. Radioactive byproduct materials were researched and developed, as well as stored, processed and synthesized into labeled compounds for distribution to authorized recipients. A labeled compound is a chemical substance "tagged" with a radionuclide that acts as a tracer. The radionuclides used at the Fort Mims facility were carbon-14 (C-14) and hydrogen-3 (H-3 or tritium).
The Fort Mims facility is approximately 26 km [16 mi] to the northwest of St. Louis, Missouri. The site is located on 0.4 ha [1 ac] in a commercial/light industrial park. The surrounding area is primarily industrial and urban. The Fort Mims facility was built in 1968 and was expanded in size in 1981. During construction activities, the septic tank was buried under building additions and the facility was connected to the St. Louis Metropolitan Sewer District. Work at the facility was primarily conducted in a two-story building consisting of approximately 1,858 m2 [20,000 ft2] of laboratory and office space. The building was constructed with cinder block, sheet metal, and wood on a concrete slab.
The SAC Fort Mims facility was a byproduct materials production and distribution operation. In 1974, the NRC issued Radioactive Materials License, 24-16273-01, to SAC for the possession and use of C-14 and H-3 for research activities and for the production of labeled compounds for commercial distribution. The maximum amounts of radioactivity on site during manufacturing were 444 GBq [12 Ci] of H-3 in 1998 and 21.1 TBq [570 Ci] of C-14 in 1991. When the facility stopped operating in 2008, only 81.4 GBq [2.2 Ci] of H-3 and 777 GBq [21 Ci] of C-14 were on site. Later in October 2008, SAC submitted the decontamination and decommissioning plan (DP) to the NRC. SAC contracted with Philotechnics Limited to remediate and decommission the facility under a reciprocity agreement with the NRC using Philotechnics' Massachusetts Radioactive Materials License No. 56-0543. By March 2009, SAC shipped all inventorial material and accumulated remediation wastes to authorized recipients. Residual and localized areas of high H-3 and C-14 contamination, however, remained on interior building surfaces, materials and pipes, and ventilation ducts. In May 2009, the NRC approved SAC's DP and amended the license to allow for remediation of the site using a four-phased approach.
The first phase was the remediation of the Fort Mims two-story building by removing the ventilation and waste disposal systems in addition to all office and laboratory materials and equipment. Phase 1 also included characterizing the surrounding soil. Surface soil samples collected in 2003, 2007, and 2008 indicated the areas to the north and west of the building were contaminated with C-14. In July 2009, the NRC verified that the building met NRC's radiological unrestricted dose limits and Phase 1 was completed. The second phase was the demolition of the building down to the concrete slab (completed in October 2009) and the removal of the slab (completed in May 2010). The third phase began in November 2009 and used soil borings to locate and characterize the septic tank area. During the soil survey, SAC identified localized surface and subsurface C-14 contamination above previously approved limits in the DP. In December 2010, SAC requested the NRC to amend its DP to include site-specific revised release limits for C-14 and H-3 in the soil which would allow the site to be released for unrestricted use. In February 2011, SAC requested the license to be amended by the NRC to release the Fort Mims site for unrestricted use. The NRC requested additional information regarding the septic tank area in March 2011 and groundwater impacts in August 2011, to which SAC responded in April 2011 and March 2012, respectively. In August 2013, the NRC informed SAC during a public meeting that they would need to revise their DP to include site-specific release limits. The NRC also informed SAC that additional site characterization data was necessary. From 2015 to 2018, SAC collected additional soil samples, installed groundwater monitoring wells, and developed site-specific C-14 sorption data. In 2019 and 2020, SAC submitted their revised DP and request for license termination. The NRC has accepted the license amendment application and is conducting a detailed technical review.
3.0 Major Technical or Regulatory Issues
4.0 Estimated Date For Closure
Page Last Reviewed/Updated Wednesday, March 24, 2021