On August 9, 2023, the U.S. Department of Energy’s Federal Low-Level Waste Disposal Facility Review Group (LFRG) voted to approve the Compliance Evaluation of DOE/RL-2019-52 Rev. 2, the Hanford Site’s Composite Analysis (CA). This approval is the successful culmination of a long and expansive project led by INTERA staff across multiple contracts necessary to maintain the waste disposal authorization for all the Hanford Site’s low-level disposal facilities.

When INTERA first began work on the Hanford Site on October 1, 2008, as a pre-selected subcontractor to the new CH2M HILL Plateau Remediation Company (CHPRC), the only scope granted to INTERA was to complete the Hanford Site CA. That was it; everything else we have done at Hanford since then has been organic expansion of our scope as we demonstrated value. Ironically, we didn’t commence work on the CA until June 2015 due DOE directives to delay this work until the Tank Closure and Waste Management EIS was completed.

But in fact, the history of this effort goes back even further. INTERA was tasked with updating the original Composite Analysis, which was a rapid effort completed by Pacific Northwest National Laboratory (PNNL) in 1998 to comply with a new DOE directive to prepare such an analysis to account for the all-pathways dose resulting from all contributing radiological sources to provide a comprehensive evaluation of cumulative dose to the public from this DOE site after site closure. It was widely acknowledged that a more comprehensive update of this initial CA was needed. INTERA’s Will Nichols was on the team that commenced work in 2001 to update the Hanford Site CA – so he has been engaged for 22 years, performing work under four prime contractors, to see the updated Hanford Site CA completed.

Commencing work under INTERA staff leadership in June 2015 with Will Nichols as project manager. First, a planning phase was conducted to define the project. Then a scoping phase, nearly two years long, started in October 2015 to develop the technical scope and approach – including conduct of workshops to engage DOE Headquarters and Hanford Site performance assessment managers in the process. This culminated in the issue of a Scoping Summary document supported by a series of Technical Approach documents in 2017, which were approved by the Hanford Site Groundwater/Vadose Zone Executive Council. That approval allowed INTERA to move into the analysis phase, in which models and tools were developed, evaluated, applied, and used to support the writing of the CA document itself. The analysis phase (2017 to 2020) saw the peak of the project work, which engaged many INTERA staff across multiple offices. Many new tools were developed, and the state of the art in vadose zone modeling was advanced significantly for Hanford in the process. The analysis phase culminated in the Revision 0 document delivered to the LFRG for review in December 2020.

The LFRG review was an arduous process. Workshops were provided by INTERA staff totaling 40 hours of technical presentation to the LFRG review team just to introduce the scope, approach, and organization of the modeling and documentation. Then a week-long onsite review followed. The review team identified 8 Key Issues (things that must be resolved before the analysis could be approved as a basis for amending the Hanford Site’s Disposal Authorization), 15 Secondary Issues (things that could be resolved along with Key Issues or in the maintenance program), and 18 Observations. Additionally, the LFRG review team granted us six Best Management Practices – welcome praise on our work that included our QA/QC program, our communication strategy, and our approach to dose calculations. Issue forms identifying corrective actions were prepared, vetted, and approved by LFRG to chart the path to approval.

INTERA staff returned to work in October 2021, for this part under Bob Andrew’s leadership, to revise the analysis to address all the Key Issues, Secondary Issues, and Observations by performing the corrective actions. This resulted in Revision 1 of the CA document in spring 2022, which was submitted with updated issue forms to the LFRG for approval. Upon further review, the LFRG identified 2 Key Issues and 5 Secondary Issues that were, in their judgment, not closed. This required another round of amended corrective actions to be identified and approved, and in October 2022 the INTERA team returned to the work again, under Will Nichols’ direction again, making further revisions to modeling calculations and documentation to attain approval. Revision 2 of the document and supporting documentation was submitted in spring 2023 to the LFRG for approval. Coordinating and supporting the LFRG co-chairs finally enabled the closure of all Key Issues and all but two Secondary Issues, as signified by the LFRG approval vote on August 9, 2023.

Maintenance of the Hanford Site CA is a critical part of Hanford Site operations because it enables disposal of low-level radioactive waste in Hanford’s onsite disposal facilities: the Environmental Restoration Disposal Facility, the 200 East and 200 West Low-Level Burial Grounds, and the Integrated Disposal Facility. It will support additional performance assessments yet to come for tank disposition. The tools and models INTERA developed to complete the CA have become the backbone of supporting CERCLA operable unit decision processes and tank disposition efforts, including providing the foundation of the Cumulative Impact Evaluation (CIE) as well.

This work was featured in The Central Plateau Cleanup Company’s (CPCCo) Newsletter, Connections, and can be viewed on pages 4-5 HERE.