A 3,396-foot-long, 30-inch-wide floating platform covered with 'akulikuli plants would quickly reduce the levels of nitrogen, phosphorus and algae in the Ala Wai Canal, according to Natural Systems Inc., the private company applying for the permit.

The process is known as phytoremediation, or using plants to treat environmental problems.

The phytoremediation platform would stretch from the Manoa-Palolo drainage canal to near the Waikiki-Kapahulu Public Library if the board approves a right-of-entry permit. A second platform, 50 feet long, would cross the canal at the very end.

Morris Takushi, a director of Natural Systems, said the company has received permits for the project from the U.S. Coast Guard and the U.S. Army Corps of Engineers, and the platforms are floating in sections nearby waiting to be put in place if approved.

"We have it all ready to go," Takushi said. "It's at the (Ala Wai) golf course, all lined up in the stream and the plants are growing already."

Plants growing hydroponically on rafts would float in the Ala Wai Canal, their roots dropping 3 to 5 feet into the water. The roots' nutrient uptake would then improve the quality of the water. Bruce Asato • The Honolulu Advertiser

Phytoremediation depends on plants that can extract hazardous substances from soil and water.

In this project, one of the plants that are known in Hawai'i as 'akulikuli would be grown hydroponically on floating rafts and their roots would drop 3 to 5 feet into the water. Bacteria and microorganisms then would colonize the roots and improve water quality through their nutrient uptake, Takushi said.

The company has done similar projects at the Four Seasons Hualalai Hotel on the Big Island and in a canal in Fuzhou, China, he said.

Natural Systems consultant Wenhao Sun said it would cost between $1 million and $1.5 million to run a platform the length of the canal to keep the water clean on a long-term basis.

The Ala Wai Canal is not a stream but part of the island's drainage system and is polluted by urban chemicals washed down from vehicles and homes, said Watson Okubo, with the state Department of Health's clean water branch.

"We know the water quality in the Ala Wai is not good," Okubo said. "People throw all kinds of stuff on the streets, wash whatever they want down the road into the gutter. They just get rid of it but it has to go somewhere. That somewhere is the Ala Wai Canal."

The canal is heavily used by canoe paddlers and kayakers. Staph infections are common when the canal's water gets into an open wound. Anyone who falls in the water is advised to take a thorough shower as soon as possible.

"We don't recommend swimming in the Ala Wai," Okubo said. "Basically you are swimming in a drainage ditch."

In 2003, the state completed a $7.5 million dredging of the canal and removed 185,801 cubic yards of trash, debris and muck from the Waikiki waterway.

The 2-mile canal was dredged to a depth of 6 to 12 feet after two decades of sediment and debris had left the canal only inches deep in sections.

Most of the sediment was taken by barge to a federally approved ocean dumping site about four miles off the coastline at Honolulu International Airport, but workers removed 1,650 cubic yards of sediment that officials say was heavily polluted from a 400-foot section near Kapahulu Avenue where the new platforms will be located. That material was taken to a disposal site at the airport's reef runway for treatment.

The current demonstration project will not remove heavy metals such as lead, mercury and copper, which were found in the water during the dredging project, but will remove other pollutants, leaving a much cleaner canal, Takushi said.

"We know it will work," he said. "It will help clean it up, keep it healthy and double the time before dredging is needed again."

The floating phytoremediation platform will be anchored to the bottom and located about 20 feet from the mauka bank of the canal, leaving room for paddlers to navigate the waterway, Takushi said.

Shelly Gilman, secretary of the Hawaiian Canoe Racing Association, wrote a letter of support for the project, which has been submitted to the Land Board.

"Our interest centered on the goal of the project: Improve water quality in the Ala Wai Canal with minimum impact to paddlers and others who use the canal for recreation," Gilman wrote Nov. 1.

Gilman said the company is working with canoe clubs to make sure their teams have access to the canal for the duration of the project.