Aquatechnex, LLC White Paper

Options for Water Lily/Floating Island Removal

Version 1.0 November, 2009

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Options for Water Lily/Floating Island Removal

Control of White Water Lilies The White Water Lily is listed as a noxious aquatic weed in Washington State. As a class C weed, it's control is not mandatory, but many lake associations choose to target this plant. It can form dense mats that prevent recreational use of infested areas. These mats can also degrade many water quality parameters critical for fish and wildlife. As lakes age, these plants can begin to significantly contribute organic fill that eventually converts the lake system from an open water body to wetland.

Generally the most cost effective control measures involve the application of EPA registered aquatic herbicides. Products like Aquamaster or SePRO's AquaPRO with the active ingredient glyphosate are very effective. This material is applied as a foliar spray to the lily pads after the plants have flowered and it trans-locates well controlling the entire plant the root systems. Another approach is to treat with Renovate herbicide, active ingredient triclopyr. While the herbicide mode of action is different and more selective for this species, it also controls the entire plant.

One of the drawbacks to these applications in Washington waters is the potential creation of "mud islands". Some time after the lily grow dies back and as the dead root masses in the sediments decay, gases created by that process can cause buoyancy and the root masses and associated sediments can float. The sediment type generally is a primary factor in how pervasive this problem may be. Once these islands form, they can be blown around the lake lodging against private property and become problematic.

While generally more costly, there are mechanical options for control of these noxious weeds that work well. There are also tools available to assist in the management of the mud islands that can be an issue.

This white paper will discuss these options and present some ideas for consideration for those combating these invasive species.

Hydro Rake Option Conventional aquatic weed harvesting operations often target White Water Lily growth. This method cuts and collects the lily pads and stems from the water column. This relief can be temporary however. Lily pad communities have extensive root and rhizome systems in the lake hydro-soil. With the energy stored in these systems, lily pads can quickly re-grow.

The Hydro Rake is a self propelled floating barge with a backhoe like arm. The rake attachment allow the operator to clear both the lily pad and stem growth from the water column, but also collects the root systems from the lake sediments. The rake is lowered to the sediments and

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grabs the root masses separating them from the lake sediments. This operation is generally performed during the summer months (if local permitting allow) to provide relief and create open water.

One of the key benefits of hydro raking these species is the complete removal of the root masses in the lake sediments. The mud island conditions that can develop are caused as these plant structured die and decay causing gas buildup. With no roots to decay, no additional gas is created. In addition, the dead root material give structure to these mud islands, without the roots present the sediments generally can't lift.

Hydro Rake systems can also assist in the removal of mud island accumulation.

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Most states require a permit to conduct these operations. Those considering this option need to consult with their regulatory authorities.

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Cookie Cutter Option Once mud islands have established, they can be hard to manage. One option that has been created specifically to clear waterways of these obstructions is the Cookie Cutter.

This very specialized vessel has two large blades on the front of the unit. These provide propulsion through the water and can cut to pieces any plant mats encountered. These systems can be very effective in the role of removing mud islands or cutting them up into small enough pieced that they will drop from the water column or can be more easily dealt with.

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Site Inspection

All mechanical control operations are highly variable. In order to properly determine the project scope, budget and results each site should be inspected by a project manager familiar with these mechanical operations. These experts can meet with the local representatives of the lake, determine their needs, specify the correct mix of equipment to meet the tasks required and get a proposal generated that will effectively do the necessary work.

For more information, go to www.aquatechnex.com or contact tmcnabb@aquatechnex.com