City planners are about to begin environmental assessment work on the long-awaited Makakilo Drive extension project that would provide a second outlet for residents of the hillside community.

But when the project will actually be built, however, is uncertain due to considerations such as cost and the topography of the area.

Details will be given at a meeting from 7 to 9 tonight at the Makakilo Elementary School cafeteria. Residents will also be asked to offer suggestions on a preferred roadway alignment.

The extension would connect at a new H-1 interchange, which, on the makai side, will also be fed by the North-South Road that will help provide relief for Kapolei and 'Ewa roads. Construction of North-South Road is already well under way by the state.

There have been an increasing number of complaints from residents about the bottleneck at the lower part of Makakilo Drive at peak morning and evening rush hour.

Brian Suzuki, a city Department of Transportation Services project manager, said when the Makakilo Drive extension project will be built — and who will pay for it — has yet to be determined.

About $800,000 has been approved for the planning stage, which Suzuki said the city hopes to have completed by the end of 2008. If funding can be found, the $3 million design phase would then begin in early 2009, he said.

The steep terrain of the area could put construction of the project at an estimated $30 million.

"It's going to be quite expensive," Suzuki said. The area in question is only about one mile long, although the actual road may be longer depending on the route. City officials hope to get federal aid for the project, he said.

The portion of Makakilo Drive coming down the top of the hill on the eastern side is already being built by, among others, Castle & Cooke Homes. The company is developing the Waikaloi subdivision, which is serviced by the new section of Makakilo Drive.

Much of the proposed alignment for the final segment lies on property owned by D.R. Horton/Schuler Division. Company vice president Dean Uchida said the company owns about 115 acres along the mauka border of H-1. Uchida said Horton has no immediate plans for the property, which is currently under agricultural designation.

The parcel is not part of the 12,500-home Ho'opili project to the east and makai of H-1 that the company plans to develop. A petition is before the state Land Use Commission for that project.

Nonetheless, Uchida said, "from a regional standpoint, there's a tremendous need for another access out there," and Horton expects it will need to pay its fair share.

Kioni Dudley, acting chairman of the Makakilo/Kapolei/Honokai Hale Neighborhood Board, said he is urging neighbors to attend tonight's meeting and give their input. The extension would improve traffic conditions immensely.

"I think it's going to take 15 percent, maybe 20 percent of the traffic off of (the existing) lower Makakilo Drive," he said.

It's also important for residents to ensure that the extension will be wide enough to meet the needs of the community, and will be aesthetically pleasing with landscaping and bikeways, Dudley said.

Area City Councilman Nestor Garcia said the project has long been a priority for him and residents in the area. Work on the North-South Road interchange by the state "provides us with a firm point for Makakilo Drive to connect to the H-1 Freeway and Farrington Highway, and this is a perfect opportunity to continue moving this project forward."

Suzuki said city planners will also be on the lookout for some residents to participate in an upcoming advisory committee to assist transit officials, and hired consultant R.M. Towill Corp. in the planning phase.

Reach Gordon Y.K. Pang at gpang@honoluluadvertiser.com.