Additional work that had begun to fill more of a tunnel at the PUREX plant at Hanford came to a halt Tuesday night, after more dirt caved into the already partially collapsed area. However, the incident was not nearly as severe as the one earlier this spring.

On May 9, a sizeable area of one of the two buried railroad car tunnels at the PUREX plant at Hanford collapsed, leaving a sizeable sinkhole, and some slight radiation release detections were noted.

Work on filling the tunnels with a concrete like mixture of dirt and other materials has been ongoing, but crews stopped Tuesday night after more dirt collapsed inside. The original cave in was about 20 by 20 feet. Tuesday night's incident was significantly less, but still was enough to halt the process.

Crews are trying to fill as much of the tunnel area as possible to prevent further collapses. The tunnel in question houses 8 highly radioactive and contaminated railroad cars, which were parked there in the 1990's when the plant began to be shut down. The two tunnels were used to transport spent fuel and other radioactive materials in and out of the fuel reprocessing facility.  The tunnels slope underground to the facility, and were buried.

According to the Tri-City Herald, work resumed Wednesday morning. After the May 9 incident, officials feared the age of the tunnels would cause them to collapse, exposing the highly contaminated materials to the atmosphere.  At the time the cars were parked there, and today, the tunnels are still considered too 'hot' or hazardous for workers to actually enter and clean up.