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DOE Completes Evaluation of Hanford's Tunnel 2, Finds 'High' Risk of Collapse
The U.S. Department of Energy is submitting reports June 30 to state authorities on the structural integrity of two tunnels at the Hanford Site in Richland, Wash., and the reports conclude that both do not meet current structural codes and standards. Doug Shoop, manager of the DOE Richland Operations Office, and Alexandra Smith, program manager for the Washington state Department of Ecology's Nuclear Waste Program, spoke about the findings at a news conference.
A section of one tunnel – PUREX (Plutonium Uranium Extraction) Tunnel 1 – filled with mixed radioactive and chemical waste collapsed May 9, 2017, at the Hanford Nuclear Reservation, and the following day, the department issued an order requiring DOE and CH2M HILL Plateau Remediation Company to immediately assess the integrity of the two PUREX Storage Tunnels and to take corrective actions. "This alarming emergency compels us to take immediate action – to hold the federal government accountable to its obligation to clean up the largest nuclear waste site in the country," Washington Department of Ecology Director Maia Bellon said May 10.
The tunnels are classified as "miscellaneous units" under Washington's Dangerous Waste Regulations, according to the order. The order says the company and DOE had not properly operated and maintained Tunnel 1 and "failed to keep it totally enclosed with a protective covering from the elements and from run-on." Completed in 1956, the tunnel was sealed after being filled between June 1960 and January 1965 with eight railcars filled with mixed waste, it states.
Tunnel 2 is much larger than Tunnel 1. Constructed in 1964, Tunnel 2 is 1,700 feet long and contains 28 railcars loaded with large waste containers. Shoop said the evaluation determined that Tunnel 2 is at "high" risk of localized collapse and should be stabilized as soon as possible. DOE and the contractor are studying how much backfilling was done when Tunnel 2 was built and the amount of compaction that was done; it has not been possible for personnel to enter either tunnel for decades because of the radiological hazards inside them, which makes monitoring their condition more difficult, he said.
Workers filled the hole created by the collapse, and now the agency plans to completely fill Tunnel 1 with engineered grout by the end of 2017. It has significantly increased monitoring of both tunnels, with daily walkdowns being done and surveillance cameras installed, Shoop said. He said DOE also will conduct a workshop or public forum in July to discuss possible stabilization measures for Tunnel 2 with the public.
Speaking of the conclusion that Tunnel 2 is at high risk of failure, Smith said, "It's not surprising but it's very concerning to us."
DOE was not able to definitively answer what caused the collapse but concluded that potential factors contributing to it may have included "heavy rainfall on May 4 and 5, deterioration of tunnel wood timber structural support members due to aging and prolonged environmental exposure."
The order directed the two to determine what caused the tunnel breach and to submit a structural integrity evaluation of both tunnels to Ecology by July 1, a draft report detailing actions to ensure safe storage in both by Aug. 1, and a draft permit modification by Oct. 1 that, among other things, addresses final closure of Tunnel 1 under the Dangerous Waste Regulations.