Washington State Department of Ecology

Aquatic Plant Management - Automatic Plant Control Products (Sediment Agitation)

Description of Method

Several automatic plant control products are commercially available that mechanically disturb the lake bottom to remove aquatic plants and prevent their regrowth within a well defined area. They sweep, roll, or drag repetitively over the plants and sediments to keep the area free of aquatic plant growth. These devices must be attached to a dock or post to work properly and each product requires electricity to operate. Depending on the product, up to a 42 foot radius around the dock or post can be controlled. Some products have a reserving capability, whereas others spin around a post.

The Weed Roller uses a low-voltage power unit (attached to the dock) to slowly drive a long roller (metal cylinder or pipe) set on the lake bottom through an adjustable arc of up to 270 degrees. A reversing action built into the drive automatically brings the roller back to complete the cycle. Fin-like projections on the rollers help detach plants from the sediment and remove roots. The Beach Groomer attaches to a lawn pump to propel two seven foot arms engineered with chains that turn to clear the lake bottom of weeds. The Lake Sweeper uses light weight rakes and a submerged pump to clear the lake bottom of weeds.

The ease of installation and operation varies depending upon the product. The type of lake bottom also is an important factor in selecting an automatic plant control device. It is best to install and start operating these devices in the spring before plants begin actively growing. If they are operated after plants have grown, the detached plants should be removed from the water with a rake or gathered by hand. Some manufacturers suggest preparing the area before installation by removing weeds and debris from the site and some products don't work very well after the plants have grown.

Once the plants are cleared from the area, these products can be used as little as one day per week or less to keep plants from recolonizing the area. When not in use, the equipment should be stored along side a dock or in a place where people can not accidentally injure themselves. Little maintenance is required, but these units must be removed from the water in winter in areas where lakes are expected to freeze.

Advantages

Repetitive sediment agitation suppresses the regrowth of plants in areas where it is regularly used.
Open water adjacent to docks can be created and maintained.
With some devices the treatment area can be modified by adding additional cylinders or rakes or by adjusting the travel arc.
Some products can easily be moved and can be shared by neighbors.
Operating costs are low - about the same as operating an ordinary pump.

Disadvantages

Repetitive sediment agitation will disturb some bottom dwelling animals and may interfere with fish spawning.
If plants are present, sediment agitation will cause plant fragmentation, which may increase the spread of some invasive weeds.
Sediment agitation devices can cause a depression to develop where the unit operates as the fine sediment is dispersed to other areas of the waterbody.
When the cleared area is to be used for activities such as swimming or wading, the equipment should be unplugged from the power source and moved and stored under or along side a dock. People may injure themselves if they step on the device.
These products should be removed in the winter from lakes that freeze.

Permits

Installation of these sediment agitation devices in Washington requires hydraulic approval obtained free from the Washington Department of Fish and Wildlife. Check with your city or county to determine whether a shoreline permit is required.

Costs

Purchase cost varies between products. The Beach Groomer starts at $999, but you also need to purchase a one-to-two horse power pump (about $300) to operate the unit. The other products cost approximately $2,000.

Vendors

The following list of vendors is provided for your information. It is not our intention to endorse or promote specific vendors or products and this list may not be comprehensive. Vendors who wish to be added to this list should contact Kathy Hamel at kham461@ecy.wa.gov

Crary Weed Roller by Crary, www.crary.com or toll free 800-247-7335

Lake Sweeper by Lake Restoration, www.lakerestoration.com or call toll free 1-877-428-8898.

Colman BeachGroomer, www.beachgroomer.com or call toll free 800-817-1850

Questions about this page? Contact Kathy Hamel by e-mail at kham461@ecy.wa.gov.