Motorists who travel along H-1 Freeway into Honolulu from West or Central O'ahu weekday evenings or early mornings are being warned that their commute time may get a lot slower in the Pearl City area for about six to eight months starting today.

The state Department of Transportation will conduct deck replacement repair work on the H-1 Pearl City viaduct east-bound between the H-1/H-2 merge and the Waimalu off-ramp. More specifically, the work will be along a 2,000-foot long stretch of the viaduct above the area between Lehua Avenue and Kamehameha Highway.

From 7 p.m., Monday through Thursday, to 4 a.m the following day, only two of the five east-bound lanes will remain open during construction.

What's more, about 2 to 3 a.m. on construction days, there may be only one lane open as workers pour concrete and let it set, said DOT spokeswoman Tammy Mori.

"That's to minimize the vibrations while the cement is being poured and drying," she said.

The speed limit may be reduced to 15 mph during construction periods. Motorists are advised to use alternate routes such as Kamehameha Highway or to adjust their commute times.

No work will be done on the project on weekends.

"We're taking a proactive approach by making these repairs before the road further deteriorates," said Jiro Sumada, deputy director of the DOT Highways Division, in a release. "This is one of our heaviest traveled corridors and we will try to minimize the impacts this project has on drivers, as best we can."

The $7 million project is being undertaken by Triton Marine Construction Corp., which completed a 10-week deck replacement job on the Salt Lake viaduct two weeks ago.

The Pearl City project was initiated following the repair work on the H-1 Salt Lake viaduct west-bound that was required after a large hole was discovered on the deck surface in January, Mori said.

"They're both about the same age, this (Pearl City) one was constructed in 1969," she said.

However, the extent of the work being done on the Pearl City viaduct is "much greater," she said. The Salt Lake project covered about 18,000 square feet while the Pearl City project will cover about 36,000 square feet.

DOT crews identified two cracks along the Pearl City viaduct that needed "advance repairs," one just before Lehua and the other where H-1 goes over Kamehameha Highway, Mori said.

"The crews will be working on 300 square feet per night, one work area at a time," Mori said.

Triton crews also have been working on the airport viaduct. Work there is continuing and has been confined to weekends.

That project consists of only paving repairs instead of the larger-scale deck replacements at Salt Lake and Pearl City, Mori said.

Triton is the only contractor at this time capable of doing the viaduct work, she said.