A 2 1/2-foot-deep sinkhole, 3 feet square, developed in Tacoma, Wash., when soil eroded under a 115-kV transmission tower after a cookie failed in a 10-inch sewer main. The city’s Environmental Services/Maintenance Division (ESMD) had to seal the connection before erosion threatened the tower’s stability.Hugh Messer, assistant division manager, called Tacoma Power in preparation for excavation. “They gave me a rough estimate of $100,000 to erect a temporary power pole, remove the tower, pour a new foundation after we repaired the pipe, rebuild the tower, and re-rig the dual power lines,” he says. “It would take three to four weeks.”Earlier,
