Since 2001, USACE has conducted a multi-phase remedial investigation (RI), developed a Feasibility Study (FS), Proposed Remedial Action Plan (PRAP), and Record of Decision (ROD) for Building 23 to address areas which are impacted by residual radioactivity from thorium-processing operations of monazite sands at the facility in the late 1950s under contract with the AEC. The remedy for the southwest quadrant of Building 23 identified in the ROD, dated May 2005, is “Decontamination with Removal to Industrial Use Levels.” From 2009-2013, USACE initiated remedial design/remedial action activities in accordance with the 2005 ROD, which included removal of equipment and building components with the highest reported radiological activity. Based on the persistence of low levels of residual radiological activity exceeding remedial goals on building surfaces following two phases of remediation and the difficulty of decontamination due to the complexity of the building interior, USACE and W.R. Grace reevaluated whether the remedy selected in the April 2005 ROD could be successfully completed as planned. The selected remedy was evaluated in comparison to an alternative to demolish the southwest quadrant of Building 23.
To support the reevaluation of a demolition alternative, in comparison to the remedy selected in the 2005 ROD, a conceptual design for demolition of the southwest quadrant of Building 23 was conducted. Pre-design investigations, including engineering surveys, geotechnical and hydrologic investigations, and additional radiological delineation of soil, were conducted in 2017 and the results were included in the conceptual design. Based on the design activities, the partial demolition of Building 23 (demolition of the southwest quadrant) was determined to be technically feasible. In addition, based on the results of the additional radiological delineation, which indicated exceedances of the industrial use criteria at depths not previously identified and at locations in close proximity to facility infrastructure, it was determined that excavation to remove all impacted soil (following demolition of the southwest quadrant) would not be feasible; as such, Land Use Controls (LUCs) for soil will be required.
The project team, in consultation with the Maryland Department of the Environment (MDE) and W.R. Grace, is proposing an updated remedy to address the threat to human health and/or the environment created by the presence of residual radiological activity in the southwest portion of Building 23 of the W.R. Grace, Curtis Bay Facility. The USACE prepared an Amended PRAP in 2019 to evaluate alternatives. The USACE is currently preparing a ROD Amendment where the preferred alternative is “Demolition of Southwest Quadrant of Building 23”. This alternative will minimize risk by removing the majority of building components that are contaminated with radioactivity at the site. This alternative is technically feasible and is considered the most protective of human health and the environment in the long term when compared to the other alternatives assessed as part of the 2019 Amended PRAP.
Upon completion of the demolition of the southwest quadrant of Building 23, a Final Status Survey (FSS) will be conducted consistent with MARSSIM requirements to verify that remedial goals are met for the remaining building components and ensure that the remedial action objective has been achieved. LUCs would be used to ensure that proper actions are taken any time the soil beneath the southwest quadrant of Building 23 is exposed, and five-year reviews by the government would be required.