KIHEI, Maui — An additional $600,000 is being spent to replace cracked plastic planks on the never-opened coastal boardwalk at the Kealia Pond National Wildlife Refuge.

Although completed in January 2005, the $2.2 million boardwalk has remained closed because of the problem. Repairs were stalled while those involved in the project sorted out who was responsible for the damage and how to rebuild the 2,200-foot boardwalk, meant to provide a platform for birdwatchers at the 700-acre refuge.

The Federal Highway Administration, which provided most of the funding for the project, and contractor Central Construction Inc. of Kahului reached an agreement to split the additional cost of removing the damaged materials and replacing them with a plastic/wood composite made by Trex Co. Inc., said Barbara Maxwell of the U.S. Fish and Wildlife Service.

The boardwalk, located on Ma'alaea Flats along North Kihei Road, initially was constructed with decking, handrails and other components made from recycled plastic milk jugs. The materials were made by Aloha Plastic Recycling of Maui, which is no longer in operation.

Soon after installation, the boards began cracking, but there were questions about whether the problem was with the decking material or with construction specifications that called for installation using nails instead of screws, which normally are used for plastic boards. Most of the cracks were found around the nails, and many of the nails had partially worked their way out of the planks and were protruding slightly from the deck surface.

Maxwell said that subsequent structural testing indicated there were "quality issues with the product."

Tom Reed of Aloha Plastic Recycling, who could not be contacted to comment, earlier disputed there were problems with the Maui-made materials, which he claimed were improperly installed. Reed also reported that despite a public campaign to collect 1.5 million plastic gallon jugs for the boardwalk, he had to import 90 percent of the recycled plastic used for the project.

The well-known, commercially available product manufactured by Trex Co. is made from recycled plastic grocery bags, reclaimed pallet wrap and hardwood sawdust, according to refuge manager Glynnis Nakai. "The company estimates it uses about 50 percent of the recycled grocery bags available on the market," she said in a statement.

"We know it's been a lengthy process, but we want to ensure the boardwalk offers a safe and enjoyable experience for visitors."

Work to rebuild the boardwalk started last week, and it is not known when it will finally open, although Maxwell said it would take months.

The Kealia Pond National Wildlife Refuge includes some of the last remaining natural wetland habitat in Hawai'i. Hawaiian stilts, or ae'o, and native coots, 'alae ke'oke'o, live there year-round, and migratory ducks and shorebirds visit in the fall, winter and spring. Kealia Beach, next to the boardwalk, is a nesting ground for the endangered hawksbill turtle.

The coastal boardwalk includes three kiosks, a bridge over a pond outlet and a small parking lot. Wildlife officials are working on interpretive panels that will be installed along the walkway.

"Although the boardwalk has never been opened, we know people are using it," Nakai said. "For safety reasons, we ask that everyone stay off the boardwalk, both because of the cracked boards and to stay out of the way of the construction crew."

Reach Christie Wilson at cwilson@honoluluadvertiser.com.