Gaseous Diffusion Plant (GDP) operations generated hazardous, radioactive, mixed (hazardous and radioactive), and nonchemical (sanitary) wastes. Past operations also resulted in soil and groundwater contamination at areas located within plant boundaries. Construction of the OSWDF creates a place for excavated contaminated soil, facility demolition debris and general site clean-up debris to be disposed. The demolition of the X-326 Process Building is an example of this with 165,000 cubic yards of debris disposed. Soil excavation is also a part of the cleanup strategy. With the help of the Site-Specific Advisory Board (SSAB) at Portsmouth, a plan was created to excavate landfills and plumes to use as fill for the OSWDF. Currently, at the Portsmouth Site, the second of the three large process buildings, the X-333 Process Building, has completed deactivation and will be the next process building demolished. The third building, X-330 Process Building, is currently undergoing deactivation with demolition to following.
In 1989, DOE signed a Consent Decree with the State of Ohio and an Administrative Consent Order with the Environmental Protection Agency (EPA). This officially began the 20-year environmental management program at the Portsmouth Site. The Consent Decree required DOE to complete investigations to determine the nature and extent of any environmental contamination that exists, complete alternative studies, and implement corrective actions as needed at Portsmouth.
During the mid-1990s, nearly 1,000 groundwater monitoring wells were installed in and around the 3,777-acre plant site, tens of thousands of soil samples were taken at various depths, and five groundwater contamination areas or plumes were identified from sampling results. Today treatments are still in place at each plume and additional cleanup actions are in operation.
Integrated Project Portfolio
The Decontamination & Decommissioning Program at the Portsmouth Site addresses deactivation, demolition and disposal of approximately 415 facilities currently identified on the Portsmouth Site. This includes the three gaseous diffusion process buildings that housed the process equipment and span the size of 158 football fields.
Other structures include support facilities such as electrical switchyards, cooling towers, cleaning and decontamination facilities, water and wastewater treatment plants, maintenance and laboratory facilities, and storage and office buildings. D&D activities will eliminate groundwater contamination sources and reduce surveillance and maintenance costs of the facilities. Less money is spent on demolished facilities because maintenance costs are decreased.
In 2020, construction of the On-Site Waste Disposal Facility (OSWDF) began. Approximately 21 acres of waste disposal capacity, a 32-acre soil management area, and a 300-acre footprint is the size of the OSWDF. When a process building is demolished, the waste of the building is placed in the cells of the OSWDF. There are 12 total cells, or sections of space, in the disposal facility. The Waste Disposition records of decision (ROD) created in 2015 calls for a combination of off-site shipping of more contaminated demolition debris and disposal of lower-level waste in the OSWDF.
Safe, efficient, and cost-effective waste disposition is key to continued progress in the legacy uranium-enrichment cleanup mission. To date, more than 163,000 cubic yards of Portsmouth disposal debris has been placed into the OSWDF there, along with 379,000 cubic yards of engineered-fill soil from legacy groundwater plumes under excavation. Disposal of the last remaining waste from the demolition of the X-326 Process Building was completed on August 24, 2023.
By Fiscal Year (FY) 2033, PPPO expects to complete the construction of all necessary disposal cells at the Portsmouth OSWDF to align with schedules for completing remaining D&D activities. By FY 2031, PPPO will ship deactivation waste not suitable for on-site disposal, and complete waste placement of demolition debris from the X-333, and the rest of the site (including old landfills and groundwater-contamination plumes) into the OSWDF. This will include completing excavation of the 5-Unit Soil Remediation Project, X-749A and X749B soil remediation projects, and the X-326 and X-333 Process Buildings concrete slabs. A planned cap for the OSWDF is also expected to begin construction during this period.
In order to obtain engineered fill for the OSWDF, Portsmouth’s Site-Specific Advisory Board (SSAB) recommended tested contaminated landfills and plumes could be used as the fill if excavated. The result will be an approximately 1,000-acre industrial site available for transfer and redevelopment as the DOE cleanup mission winds down. The first plume excavated was the X-740 Plume. The contamination was caused by trichloroethylene (TCE) which is a lubricant that was used during operations. The four-acre plume provided 25,000 cubic yards of fill for the OSWDF.
In the near term, PPPO will implement Corrective Measures of the Deferred Units (DUs) in accordance with the latest Ohio EPA-issued Decision Document. Excavation of the X-231A/B was completed on Sept. 26, 2023, and will be followed by the remaining areas of the 5-Unit Plume. Removing soil from these areas provides engineered fill to support the debris placed into the Portsmouth OSWDF while addressing previously capped and closed landfills.