GeekWire » Seattle Tunnel Partners (STP) has released a video of construction crews performing routine maintenance on Bertha, the tunnel boring machine, which includes power washing the cutting head and replacing cutting tools that weight 75 pounds each. Bertha is outfitted with 700 cutting tools (or teeth). During this maintenance stop STP has inspected 400 teeth, replacing 25, and remains on schedule to resume digging at the end of July.