Crews knew they had entered this zone when they probed 100 feet ahead of their tunnel face and found large amounts of groundwater. Before crews could do any mining forward, they had to inject 66,000 pounds of grout (think liquid cement) into the rock ahead of them to fill cracks and voids in the earth. That’s enough to fill up the water tank pictured below! Grouting fills these voids and keeps groundwater out of the tunnel. It keeps our miners safe and allows tunneling to continue.
Grout is taken by rail to tunnel heading and mixed inside of the tunnel. In November alone, approximately 423,000 lbs. of cement was injected into rock fractures, filling cracks ranging up to 1.5 inches in width.