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May 22, 2020
Event: Public Comment Period for Stabilization of Disposal Structures at Risk of Failure and Time Critical Removal Action
Category: Comment Period / Feedback Opportunity
Event Date: 03/23/2020 – 06/29/2020

Update: This comment period has been extended until June 29, 2020.


This is a message from the Tri-Party Agreement agencies

Public Comment Period and Online Public Meeting on Stabilization of Disposal Structures at Risk of Failure and Time Critical Removal Action

Following the partial collapse of a waste storage tunnel at the Plutonium Uranium Extraction Plant (PUREX) in May 2017, the U.S. Department of Energy (DOE) and contractor CH2M HILL Plateau Remediation Company (CHPRC) analyzed other older structures in Hanford’s former plutonium production area (the Central Plateau) to determine if any other structures represented a risk of collapsing.

In 2018, CHPRC produced a report identifying 27 structures that may require risk-mitigation work. The Department briefed these results to Hanford regulators and stakeholders. In 2019, the department and CHPRC identified 11 of the 27 structures that required further analysis. In October 2019, CHPRC produced a report on those 11 structures.

The results of the evaluation and recent subsidence at one liquid waste disposal structure (216-Z-1) indicate a number of structures are overstressed and at risk of age-related failure, resulting in the potential to spread contamination to the environment. Three of the identified structures are the 216-Z-2 Crib, 216-Z-9 Crib and 241-Z-361 Settling Tank, which are located in the PW-1 Operable Unit, within the Plutonium Finishing Plant demolition boundary.

DOE is proceeding with a Time Critical Removal Action under the Comprehensive Environmental Response, Compensation and Liability Act to address these three underground structures. The structures received liquid waste during Hanford’s plutonium production operations and contain residual radioactive and chemical contamination. DOE and CHPRC are preparing to stabilize the structures by filling them with engineered grout.

Planning for the stabilization work is underway, including design, regulatory documentation and a subcontracting approach for materials and services. Fieldwork preparations will begin in the coming months, with grouting of the two smallest structures planned to begin this summer after Plutonium Finishing Plant demolition activities are completed. Grouting of the larger structure is anticipated to be completed within the year. Grout has been used in other stabilization projects on the Hanford Site (most recently PUREX Tunnels 1 and 2) to expedite risk reduction. The use of grout will provide additional protection, while not precluding future remedial actions or final closure decisions.

A 2011 Record of Decision (ROD) exists for these three waste sites. The final remedy for these waste sites is to remove the structures and remove, treat and dispose of contaminated soil from the 216-Z-2 Crib and the 216-Z-9 Crib. The final remedy for the 241-Z-361 Settling Tank is to remove the remaining sludge from the tank and grout in place, while the Remedial Design / Remedial Action Work Plan for this tank considered removing it entirely. The agencies have agreed that the Time Critical Removal Action will not change the selected remedy for the 216-Z-2 Crib, 216-Z-9 Crib and 241-Z-361 Settling Tank.

The previously scheduled public meeting is being moved to an online only format and will be held May 7, 2020, at 5:30 p.m. PST. To participate via GoToWebinar, please follow the instructions below:

          Click the GoToWebinar link:;
          ID #: 776-461-667

         1.     Dial the appropriate number: 376-3622 (local) or 1-877-401-5229 (toll free)
         2.     Enter in the Conference ID _520605 _ (followed by pound key)


The 90-day public comment period runs from March 23 to June 29, 2020

Supporting documentation is available on the Hanford website. Please see the summary fact sheet below. Questions? Please cntact Jennifer Colborn, at

To request disability accommodation, please contact Jennifer Colborn,, 509-376-5840 at least 10 working days prior to the event. DOE makes every effort to honor disability accommodation requests.

Fact Sheet (PDF)
Meeting Presentation

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