A small steel grate caused a huge traffic problem yesterday morning for commuters heading into town on H-1 Freeway from Leeward and Central O'ahu.

The 1-by-3-foot grate, one of a series of grates used to cover a storm drain in the shoulder lane, popped loose sometime before 6 a.m. Drivers are allowed to use the shoulder lane during morning peak traffic hours.

After the grate came loose, a series of vehicles dropped a wheel into the newly created hole. Wheels smashed into the concrete edge of the hole, or the next steel grate.

The result: dented rims, damaged tires, suspension issues and a monumental traffic backlog.

"We know that between 15 and 20 vehicles had some sort of damage," said state Department of Transportation spokesman Scott Ishikawa.

"We managed to get a repair crew out there by 7:15 (a.m.) to weld the grate back in place," Ishikawa said.

While morning radio-show traffic monitors credited a female commuter with getting out of her car and dragging the grate back over the hole, Ishikawa said her efforts may have added to the delay.

"After our repair crew got there, they had to spend some time figuring out which of the grates was loose," Ishikawa said.

The repair workers blocked off a stretch of shoulder lane and right-most regular lane on the Waiau viaduct while the loose grate was located and welded back into place, Ishikawa said.

A work crew was scheduled to return to the area at about 10 a.m. today to check on the remaining grates and refasten them if necessary.

State transportation officials did what they could to reduce the backlog of in-bound traffic by opening the Zipper Lane to all takers and leaving it open until 9:30 a.m. instead of the usual 8:30 shutdown, Ishikawa said.

Even so, some commuters from 'Ewa Beach and Mililani estimated the missing grate and resulting problems added about 90 minutes to their morning drive.

Reach David Waite at dwaite@honoluluadvertiser.com.