Backhoe pulls Lake Wilson weeds

By Walter Wright
Advertiser Staff Writer

WAHIAWA — Making a 31-ton amphibious Caterpillar backhoe dance like a ballerina on a sea of weeds, city heavy equipment operator Allen Kaaihue yesterday launched an effort to clear Lake Wilson of the voracious plant Salvinia molesta.

A noxious weed that has completely covered Lake Wilson is being removed by an amphibious excavator. Richard Ambo • The Honolulu Advertiser

She said when she and her husband, George, got home yesterday evening, they looked out at the lake and saw water for the first time in months.

Eric Hirano, head of engineering for the state Department of Land and Natural Resources, said officials in a city-state-federal task force estimate that Kaaihue managed to reduce the solid coverage of weeds on the lake by one acre in three or four hours of work yesterday.

If the task force can increase the extraction sites to five, using more amphibious backhoes, some land-based conveyor systems and other methods, it may be possible to rid the lake of the noxious weed in 28 working days, Hirano said.

Aquatic experts say if the weed isn't removed by July, a massive fish kill could occur as the lake shrinks in size and oxygen levels plummet.

Another key will be to apply approved herbicides to keep the Salvinia from growing.

Hirano said the task force expects to ask boaters and other volunteers eventually to pluck the weed from small areas.

Salvinia is an aquatic pest in warm-weather areas of the Mainland. In Hawai'i, the plant went from covering a few acres near the lake's dam in November to coating virtually the entire surface of the lake, including both of its extended arms, by January.

Yesterday's effort hit snags when the city's pontoon-based backhoe stalled with a dirty fuel filter, and the state burned out two outboard motors on boats used to haul weed closer to the backhoe by pulling on an oil-containment boom.

Kaaihue fixed the filter and returned to the fray at 4 p.m., guiding the huge machine on motorized treads across land like a tank, and through water like an old side-wheeler river boat.

The black-and-yellow machine plunged into the chartreuse lake of weeds, which bobbed and rippled away, then sucked back in.

Salvinia molesta, which infests some areas of the Mainland, covered the lake in a few months. Richard Ambo • The Honolulu Advertiser

"It's too slow," George Watanabe said, suggesting the state use some sort of coal mineistyle conveyor belt to send buckets out into the lake and drag the weed back ashore.

Stanley Wong, who pumped 212 gallons of diesel from a stainless-steel city tank truck into Kaaihue's machine, said Watanabe was the first of many "shoreline superintendents" to watch the project.

"Come back tomorrow, bring your folding chairs and your pupus," he told Watanabe.

"I'm gonna bring a lunchwagon, because there's going to be crowds here," Watanabe replied.

Kaaihue said helping to clear the lake is a personal challenge.

"I have a passion for engines — I enter backhoe contests — and I enjoy the work," said Kaaihue, who has been operating heavy equipment for 20 years. He became the only man in the state who knows how to run the rig when he helped to clear Ho'omaluhia Park waters of Salvinia some 18 months ago.

"I don't know how long this is going to take, but I just do the best I can do. Anything I take out of the lake is a good thing," Kaaihue said.

By day's end, he had dumped on shore a row of Salvinia 6 feet high, 6 feet wide and 90 feet long.

Amy Watanabe said she couldn't understand why the state didn't do more when she called them last April to report large patches of Salvinia floating on the lake.

"It would have been a lot easier to take it out then," she said.

Reach Walter Wright at wwright@honoluluadvertiser.com or 525-8054.