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