Planning and design work for a long-awaited, multimillion dollar improvement project for Diamond Head State Monument is finally expected to wrap up this fall, and work could start early next year.

The $4.4 million project will include improvements to the historic 0.8-mile summit trail, the addition of a small, one-way loop at the summit for hikers going back down and some rockfall mitigation work. Legislators appropriated the money for the project in 2007, and design work kicked off mid-2008.

It's taken more than a year to finalize the design plans, officials said, because engineers have been working with resident advisory groups to ensure that safety improvements don't detract from the monument's beauty.

A key part of the project will be the addition of a new, one-way loop for hikers headed back down the trail to alleviate a gridlock near the bunker area near the summit.

The project also includes trail resurfacing.

Clark Hatch, the president of the Diamond Head State Monument Foundation, said, "The trail improvements are greatly needed," adding that the trail appears eroded in places.

Michelle Matson, of the Diamond Head Citizens Advisory Group, agreed, saying the trail is one of the most popular spots on O'ahu for both residents and tourists and needs to be properly maintained. About 2,100 people visit the monument daily. Matson said resurfacing the trail, adding the loop and making other improvements are a "necessity for the safety of our visitors."

Funding for the project also covers work to look at the feasibility of making a new pathway from the summit all the way down to the start of the trail.

Making the new trail a reality would require more funding, however.

It's still unclear how long the trail will have to be closed or how long work will last. About $2 million is available for the upcoming rockfall mitigation project.

Crews will also install safety buffers along Diamond Head Road to stop falling rocks, and the Kahala Tunnel entrance to Diamond Head will undergo repairs. Work is expected to start in fall 2010.