graphic: ISW banner, link to homepage

graphic: salvinia molesta title




image: basin area of Lake Wilson , click to enlargeJuly-August 2002 State Division of Aquatic Resources (DAR) discovered that Salvinia seemed to be multiplying and stepped-up their control efforts. By November 2002, most of the Salvinia was contained in the basin area (at the dam and spillway of the Lake) and the City & County of Honolulu (City) assisted in removal efforts using a front-end loader and dump trucks.

December 2002 Salvinia within the contained area by the basin and plants located outside of the containment area exploded in growth and took DAR and City crews completely by surprise.

January 2003 Salvinia had covered approximately 90% of the Lake's surface water area (270 acres) and posed the threat of a massive fish kill and a potential public health disaster.

January 31, 2003 Senate President Robert Bunda assembled a multi-agency government task force including legislators, congressional representatives, military services, businesses and concerned members of the community to address the eradication of Salvinia from the Lake. This group is now called the Salvinia "Partners" Working Group.

Early February The Governor designated the Department of Land and Natural Resources (DLNR) as the lead agency in addressing the infestation of Salvinia and deemed the infestation at the Lake a state priority.

By February 14, 2003 The Partners Working Group developed a 3-pronged short-term plan to address the immediate removal of Salvinia from the Lake:

image: dead fish among salvinia, click to enlargeEstablish three extraction sites using heavy equipment consisting of an excavator, front-end loaders and dump trucks with supporting services (e.g. fueling and water tank trucks, etc.). Two to four boats with oil booms would be used to round-up the Salvinia and pull it towards the extraction sites. A two to four person ground crew would also be needed to secure the oil booms on-shore and to pull the booms toward the excavator. Initially, the State, City and the Military would provide their own manpower and resources to outfit their respective extraction site. Should additional resources become available and if suitable sites are located, one to two more extraction sites would be mobilized into operation. Landowners have provided a disposal area (approximately 30 acres) in their fallow fields and will later mulch and compost the weed material for use on their planting fields.

Herbicide spraying of Aquamaster will be used to kill and/or retard the growth of Salvinia so that extraction activities can over-take the exponential growth rate of the weed. Aquamaster is an Environmental Protection Agency approved herbicide for use in aquatic environments. No special protective equipment is necessary for spray application, the herbicide is bio-degradable, has a short residual time and becomes inactive upon contact with soil.

Last prong of the short-term plan is to solicit community support and volunteers to clear areas where the main extraction efforts cannot reach (e.g. along the edges of the Lake, between fallen tree branches, areas inaccessible by boats, etc.).

February 15, 2003 DLNR Chairperson Young assigned DLNR's Engineering Division to take the lead in the eradication of Salvinia at the Lake and statewide.

February 18, 2003 The City mobilized and started extraction efforts at Site #1 located in the basin area near the dam and spillway of the Lake.

image: boats and booms rounding up salvinia, click to enlargeFebruary 19, 2003 The DLNR closed Wahiawa Freshwater State Park for public use and this area will be used for the State's extraction efforts as Site #2-A.

February 25, 2003 The State mobilized heavy equipment into Site #2-A and began extraction efforts the following day.

February 25, 2003 Approval was granted by the General Contractors Association to allow for use of military resources for eradication efforts (exemption for non-competition by private sector resources).

February 20-21, 2003 Department of Agriculture (DOA) conducted test spraying of herbicide.

February 24, 2003 DOA commenced full spraying operations. It is estimated that approximately 14 acres per day can be sprayed with a minimum goal of 50 acres per week weather permitting. Spraying operations anticipated to continue for six weeks.

March 8, 2003 Hawaii Army National Guard provides 2-loaders and 6-dump trucks to assist in eradication efforts.

March 10, 2003 The Army's extraction site # 3 located across from the City's extraction site along the north fork of the lake begins operation. Extraction site # 3 is located approximately 400 yards up-stream of the City's extraction site along the north fork of the Lake.

March 14, 2003 DOA completes initial spraying of Lake's surface area covered with Salvinia estimated to be around 214 acres. Spraying operations completed 3 weeks ahead of initial estimate. DOA to monitor effects of herbicide sprayed areas for the next two weeks.

image: boat geared for herbicide spraying, click to enlargeMarch 20, 2003 Last day of extraction at State Site #2-A. Operations at site have become inefficient due to length of time necessary for boats to boom Salvinia weed to the excavator.

March 21, 2003 Mobilized two excavators to new State Extraction Site #2-B. This site is located on a peninsula in the basin area at the confluence of the North and South Forks of Lake Wilson.

March 24, 2003 U.S. Marine Corps' Waterfront Operations provides two boats with operators to assist in eradication efforts.

March 31, 2003 U.S. Marine Corps' Engineering Company (CSSG-3) provides one loader and one dump truck with operators to assist in eradication efforts.

March 31, 2003 DOA re-commences herbicide spraying along the edges of the Lake.

April 3, 2003 Last day of extraction at Army's Extraction Site #3.

April 4, 2003 Last day of extraction for one excavator at State Extraction Site #2-B. Last day of herbicide spraying along the edges of the Lake by DOA.


April 11, 2003 Mobilize equipment and clear new Army's Extraction Site #3-B. This site is located on the South Fork of Lake Wilson in the East Range of Schofield Barracks Military Reservation.

April 14, 2003 Received notice from the City that they will cease operations on Saturday, April 19, 2003 and are requesting for $276,000 in reimbursement from the State for removal costs.

April 14, 2003 Army begins to remove large debris (tree stumps and branches, timbers, etc.) from Extraction Site #3-B and will begin extraction activities the following week.

April 14, 2003 Boats begin operations of extracting weed material along the edges and small coves of the Lake.

April 19, 2003 City ceases operations.


May 6, 2003 - Army concludes bulk extraction at the East Range


Total amount of weed cleared via bulk extraction sites = 50,000 cubic yards (does not include amounts from followup maintenance by boat crews)

May 24 2003 - Department of Land and Natural Resources reopens the popular state park at Wahiawa Freshwater Recreation Area for public use of shore portions. The park reopening, after nearly 3 months of closure, follows successful completion of intensive bulk extraction activities by City and County, state and federal and military agencies to remove extensive growths of the Salvinia molesta aquatic weed that at one point covered an estimated 95 percent of the lake's 300-acre surface area.

Smaller-scale work daily work continues to eradicate remaining amounts of Salvinia along the lake's 20-mile perimeter.

Freshwater fishing clubs also assisted DLNR with volunteer cleanups of Salvinia at Lake Wilson on:

June 14, 2003 - Wahiawa Public Fishing Area (Lake Wilson reservoir) is reopened to boat fishing. Division of Aquatic Resources posts a sign at the boat launch ramp asking fishermen to kokua and assist in the removal of Salvinia from reservoir. As part of its necessary maintenance control for Salvinia, the Division of Aquatic Resources will conduct perimeter shoreline spraying with an EPA-approved herbicide on the second and fourth week of each month, on Mondays, Tuesdays, and Wednesdays (except holidays) until the end of the year. The boat launch ramp will be closed and chained on the days when spraying will be conducted. The public's understanding and kokua is appreciated.

July 30, 2003 - Due to successful maintenance control spraying for Salvinia, Division of Aquatic Resources reduces boat launch ramp closures to once a month only on the first Tuesday of each month through the end of the year.

August 11, 2004 - More than a year after successfully controlling a crippling infestation, Lake Wilson remains almost completely Salvinia-free. DLNR's Division of Aquatic Resources does monthly monitoring of the lake. Presently the only location where a few Salvinia plants still exist is on the South Fork amidst an area of California grass less than one acre in size. This area is completely enclosed by a floating oil boom to prevent any chance of the small plants from escaping, and the California grass which provides cover is being removed with the use of an aquatic harvester.

graphic: flower button, link toAbout Salvinia molesta
graphic: flower button, link toTimeline: Eradicating Salvinia from Lake Wilson
graphic: flower button, link toDLNR Press Release: Lake Wilson Closure: blue ball graphic, link toHTML page blue ball graphic, link toPDF (86k)
graphic: flower button, link toLake Wilson Project Status
graphic: flower button, link toPhoto Gallery
graphic: flower button, link toSalvinia molesta flier (624KPDF)
graphic: flower button, link toDLNR homepage

e-mail graphic, link to send comments about this web site and to contact DLNR  e-mail DLNR with comments or concerns