Kapolei residents may see relief from bumper-to-bumper traffic through the heart of town as the area's primary private developer teams up with the state to create the Kapolei Interchange.

Kapolei Property Development LLC, an affiliate of the James Campbell Estate, will contribute $2 million toward the planning and design of the interchange and also has provided the land on which the interchange will be built.

"It will help to alleviate traffic and give people another way in and out of Kapolei," said Donna Goth, president of Kapolei Property Development. "It's a part of our regional traffic program."

It will allow drivers to get off Kamokila Boulevard at Wakea Street, near Zippy's, and connect directly to H-1 Freeway. Officials say it will alleviate much of the morning and evening rush-hour and weekend traffic backups in the fast-growing city.

Groundbreaking is scheduled for the end of the year and construction is expected to take 18 months, said Theresia McMurdo, public relations manager for Campbell Estate.

Federal funding of $40.8 million has been earmarked by Congress for the Kapolei Interchange and a proposed North-South Road, which will connect Kapolei Parkway with H-1 Freeway, she said.

Federal funding covers 80 percent of the projects, and the state is required to pay 20 percent, said Scott Ishikawa, spokesman for the state Department of Transportation.

Ishikawa said the state is hoping to use the value of planning and design, and the land donation as part of the state's 20 percent.

"It's a complicated formula," he said. "We're still trying to determine whether state funds, if any, will be used toward the construction."

He said the first phase of the interchange is expected to cost $8.8 million, and the second phase, which would include a more complicated overpass, would cost around $20 million.

"We are very thankful KPD is working with us to speed along the timetable for these traffic projects," Ishikawa said. "Everybody is going to benefit."

Goth said the interchange is among six road projects in the area that private developers are contributing toward by paying impact fees with each development.

Reach Karen Blakeman at kblakeman@honoluluadvertiser.com.