It really doesn’t come at a great surprise that the second waste tunnel associated with the Plutonium Uranium Extraction Plant (PUREX) at the Dept. of Energy’s Hanford Nuclear Waste Site in southeast Washington is at risk of collapse. After all, the first tunnel partially collapsed in May.

Following the Tunnel 1 collapse that sent the site into emergency lockdown, DOE and its contractor, CH2M Hill Plateau Remediation Company, investigated a report detailing the current structural codes and standards of the second tunnel. They found it does not meet current standards.

“We will work closely (the Dept. of) Ecology to determine how best to stabilize Tunnel 2 and ensure the safe storage of the waste until it can be remediated,” said Doug Shoop, manager of the DOE Richland Operations Office.

The report also looked at causes of the Tunnel 1 collapse, attributed, in part, to two days of heavy rainfall leading up the collapse that exasperated the deterioration of the tunnel’s wood timber structural support.

Tunnel 1, which contains equipment exposed to radiation, will get filled with engineered grout to stabilize the tunnel, reduce risk to workers and the environment and enable future remediation of the equipment and materials in the tunnel. Crews selected the approach after analyzing stabilization alternatives.

According to the report for Tunnel 2, a review of the tunnel’s 1960s design shows that it does not meet current codes for structural integrity and that it may not be able to bear the weight of the soil above the tunnel, finding “Tunnel 2 is identified as presenting a high potential for localized collapse.”

Built of metal and concrete in 1964, the tunnel runs about 1,700 ft long and has 28 rail cars stored inside. The waste on the cars is similar to that in Tunnel 1, including equipment from Hanford’s plutonium processing facilities and other plutonium processing waste.

“We are evaluating options for using a remote capability to get a look at the general condition of the inside of the tunnel as well as to take radiological readings,” Shoop said. “We have increased our monitoring of the tunnels, including daily walk-downs and cameras that overlook both tunnels.”

A report detailing corrective actions is due by Aug. 1.

Follow Tim Newcomb on Twitter at @tdnewcomb