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A deep sinkhole has forced Renton to make emergency repairs on Rainier Avenue North, near the Renton Municipal Airport — and block traffic until Thursday morning’s commute.

A contractor began digging around the void Wednesday afternoon in the 900 block of Rainier Avenue North, said city spokeswoman Preeti Shridhar.  Traffic has been diverted around the area, she said.

The failure was caused by a rusted steel stormwater pipe, installed a half-century ago, said Patrick Zellner, street maintenance manager. The 3-foot-wide pipe broke, taking with it a concrete access vault that was poured around the pipe, he said. The vault settled and its bottom broke, he said. After some excavating, the city determined the sinkhole was about 25 by 30 feet wide, and 15 feet deep.

All lanes were blocked at 2 p.m. Traffic detour routes, marked in orange signs, begin at 87th Avenue South from the north, or Seattle side, and at Renton Avenue South for drivers approaching from the south.

Zellner said all Renton’s underground utilities are periodically inspected with video cameras.

“We’re all up against aging infrastructure, especially in our older parts of town,” he said.  Renton is 117 years old, and the street was widened over past decades from a two-lane concrete highway into an asphalt coated boulevard, with older components beneath.