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The right lane of northbound First Avenue South reopened around 3 p.m. Friday, after city crews fastened a metal plate over a former sinkhole, near the crossing of South Massachusetts Street.

That lane had been closed since early Tuesday, when a 16-inch diameter, century-old water main broke.

City agencies originally predicted a Thursday reopening, but a cement-and-soil fill mix that was poured into the sinkhole didn’t cure fast enough. City crews tried to apply blacktop pavement mid-day Thursday, but the heat of the asphalt caused moisture inside the hole to rise, making the new road surface too weak to handle traffic, according to the Seattle Department of Transportation.

The steel plate will remain for a few days, until workers can inspect the fill and decide when to complete the new asphalt surface, said Rick Sheridan, spokesman for SDOT.