Five weeks later, 25 percent less weeds at Lake Wilson
By Catherine E. Toth
Advertiser Central O'ahu Writer
Weed extraction efforts at Lake Wilson in Wahiawa have cleared between 25 percent to 30 percent of the 300-acre reservoir since work began five weeks ago.
State, city and military crews have pulled out a little more than 26,000 cubic yards of the noxious weed Salvinia molesta since work started Feb. 18.
The state Department of Agriculture completed its efforts to spray the entire lake with herbicide on March 14. In the three weeks of spraying — initially estimated to take six — crews covered more than 200 acres with the herbicide. City and state workers have begun extracting dead weeds.
"We're pulling out everything possible, whatever's available to us, as quickly as possible," said Eric Hirano, head of engineering for the state Department of Land and Natural Resources.
The state closed its extraction site at the boat ramp last Thursday because it was taking too long for boat crews to gather the weed from downstream. A new site with two excavators was opened last weekend along the basin area at the end of Malulu Place.
Personnel from Waterfront Operations of Marine Corps Base Hawai'i joined the effort on Monday, providing boats, manpower, a dump truck and a loader.
Crews continue to pull out the salvinia six days a week at three sites, working about 10 hours per day. The National Guard assists with the removal and disposal of the extracted weed on weekends.
"We're making progress," Hirano said.
Meanwhile, a volunteer cleanup Saturday at Kawainui Marsh in Kailua was successful in some areas and revealed a larger problem at another site in the wetland, said Sen. Bob Hogue, one of the coordinators of the cleanup.
"We have eradicated the salvinia in all but one ditch on the Kapa'a Quarry (Road) side," said Hogue, R-24th (Kailua, Kane'ohe). "We have eradicated all of the water lettuce with the exception of one pond on the Kapa'a Quarry (Road) side."
The weeds in the ditch and pond were hiding in brush and vegetation along the banks and will have to be removed later, Hogue said.
More than 200 people volunteered to remove noxious weeds from the marsh, including salvinia and water lettuce — another invasive species — he said.
The salvinia on the quarry road filled about half a truckload and proved to be less of a problem than water lettuce next to the levee, primarily because the city had removed the salvinia before the cleanup, he said.
But after removing more than five truckloads of water lettuce, the organizers realized that more work would have to be done to wipe out that weed from waterways along the levee, Hogue said.
"We found way more water lettuce than the naked eye could see," he said, adding that the plant was thicker and in deeper water than volunteers could reach.
Earlier, the city had sprayed the weeds with herbicide, and Hogue said he thought more of that would have to be done. He also said he would consult an expert to get advice on killing or removing water lettuce from the levee waters.
"My feeling is it will be a lengthy fight to get that invasive species out of there," he said.
The cleanup also included opening a view to the marsh and removing trash from the road.
Staff writer Eloise Aguiar contributed to this report. Reach Catherine E. Toth at 535-8103 or ctoth@honoluluadvertiser.com.
