Lake Wilson cleanup to pause
| • | Sale, transport of weed out of state's control |
By Catherine E. Toth
Advertiser Central O'ahu Writer
Despite the seriousness of an infestation of Salvinia molesta at Lake Wilson — and the weed's rapid growth rate — plans call for the state's counterattack against the noxious weed to be put on hold on weekends, state officials said.
The state had only asked the participating agencies for the use of existing resources, including manpower, and they couldn't spare any more, said Eric Hirano, head of engineering for the state Department of Land and Natural Resources, which is heading the salvinia removal effort.
"But if we think we're not extracting as much as we're hoping, we'll step up efforts," Hirano said.
With the salvinia weed producing as much as 400 tons of new growth per day, the days off will allow the plant to wipe out some of the gains made during the week. And extraction has already fallen behind the goal of having it removed within 28 working days.
"I believe they should be working 24 hours, seven days a week," said Rep. Marcus Oshiro, D-39th (Wahiawa). "This is like a forest fire. You don't stop because the sun goes down or a weekend comes around. This weed does not take a break, it does not rest, it does not take time out on the weekends. And we can't either."
The weed covers about 95 percent of the lake's surface. Crews are pulling out an average of 200 to 300 cubic feet of salvinia every day, Hirano said.
The initial 28-day estimate to have the salvinia removed has been extended, Hirano said.
"We're falling a little bit behind that schedule," he said. "We'll see how things go."
Officials also say the reinvigorated excavation effort alone isn't enough, and next week workers will begin spraying the weed with herbicide.
"Right now, with only one site, we're taking out maybe less than half of what we would like to take out per day," said Randy Honebrink, education coordinator for the DLNR's Division of Aquatic Resources. "This is a learning process. We hope as we go along we're going to be more efficient."
The herbicide, called AquaMaster, will kill the salvinia, causing it to sink to the bottom of the man-made lake. It will not harm the fish in the lake, officials said.
Labeled for aquatic weed control, AquaMaster moves through the plant from the point of foliage contact into the root system, killing the entire plant.
"(The herbicide spraying) is the most important part right now to stop its growth," Honebrink said. "Once the herbicide is applied, the plant starts to die ... and that'll be the last we see of it."
He said the herbicide isn't harmful to the environment, as the chemicals break down quickly. It will be applied directly to the foliage; the chemicals won't be released into the air.
The dead weeds will either be removed or sink to the bottom of the lake and decompose, Honebrink said.
But even that has a down side.
"When the plant dies it's even worse," said University of Hawai'i botanist Curt Daehler. "It sinks down and absorbs a lot of oxygen as it decomposes."
Reduced oxygen levels, in turn, threaten the estimated 500 tons of fish in the lake, the largest freshwater body in the state.
Oxygen levels are already low because of the salvinia having formed a canopy on the water's surface, blocking the entrance of new oxygen from the air into the water, Daehler said.
To allow oxygen to flow into the water, crews will have to clear enough salvinia from nearby locations on the lake before the herbicide is sprayed, he said.
"If you open up that connection between air and water, if there's enough water flow, you'll get the oxygen going back into the lake though it's being absorbed," Daehler said.
Next week the state will open up a second site for excavation by the boat ramp at the Lake Wilson Recreation Area, which has been closed indefinitely. Excavation is already being performed at a site behind Kemoo By The Lake condominium on Wilikina Drive.
The state is using a $150,000 federal grant to finance the lake clean-up. Lawmakers are looking for alternate sources of money from city and state budgets to finance the rest of the project, Oshiro said.
About a dozen people are working at the site every day.
Though the state hasn't said how much this is costing taxpayers, Daehler said it has to be "expensive."
"That's the downswing," he said. "You may have (raised awareness about the lake), but you're paying a price in terms of dollars and use for people. There's a trade-off there. Maybe next time we'll be more careful."
Reach Catherine E. Toth at 535-8103 or ctoth@honoluluadvertiser.com.
