COLUMBIA, S.C.- Crews are working to repair a breach in the Columbia canal that is threatening the main water supply for 375,000 people.
    
Columbia Utilities Director Joey Jaco says officials were working Wednesday to build a rock dam a few hundred feet north of the breach, which is near the city's hydroelectric plant in view of morning commuters crossing the Gervais Street bridge.
    
Jaco says officials had hoped to have the dam completed by Wednesday morning. But the normally calm waters of the canal looked more like a whitewater rapids course after days of record rainfall, making it difficult for workers to move equipment to put the dam in place.
    
Jaco says the National Guard is helping by using helicopters to bring in sandbags and says the dam should be in place sometime Wednesday. Jaco says the only danger now is for the canal to breach in a second spot. But he says the levy shows no signs of buckling.
    
The canal was built in the early 1800s and supplies 35 million gallons of water to the city's water plant each day.