Aquatic Plant Management

A Bottom Screening Project

The Jefferson County Conservation District sponsored a demonstration day of aquatic plant control methods in Lake Leland. in 1998. Lake Leland is located in the foothills of the Olympia Mountains in eastern Jefferson County five miles north of Quilcene, Washington. At that time, the south end of this lake was heavily infested with a non-native aquatic plant - Brazilian elodea (Egeria densa). The demonstration day was planned to show lake residents some management activities that they could perform to help manage the excessive growth of this noxious weed in Lake Leland.

As part of the day's activities, volunteers installed a bottom screen (also called bottom barrier) at the dock of local residents (with an appropriate permit from the Washington Department of Fish and Wildlife). The home owners constructed the screen using heavy tarp material held in shape and reinforced with PVC piping and weighted with steel rebar. This structure proved to be too flexible to move easily and long lengths of aluminum piping were temporarily used to strengthen the structure. After installation, they removed the piping. The picture to the left shows the bottom screen on the lawn where it was constructed.

Luckily a number of people showed up for the demonstration day because the bottom screen was unwieldy. It required about ten people to lift and move the screen onto the dock prior to slipping it into the water. The  on the left shows volunteers getting underneath and starting to lift the screen. When the volunteers were in place, the screen was "walked" onto the dock. Once on the dock, the screen was set down while everybody discussed the best way to go about getting it into the water (right).

The plan was to install the screen immediately in front of the dock. The day before, Jefferson County Conservation District employees and lake residents had cut and removed most of the Brazilian elodea plants growing in this area. Before cutting, these plants formed a mat on the water's surface. Cutting the plants prior to bottom screen installation served two purposes (1) to facilitate lowering the screen into the water and (2) to remove plant biomass to cut down on the amount of gasses produced by decomposing plants.

As the time came to lower the screen into the water, two boats were stationed on either side of the dock (left). Two large inner tubes were also positioned at each side of the dock. The leading edge of the bottom screen was carefully lowered onto the inner tubes. The action of the the people pushing the screen into the water and the guidance of the boaters facilitated the smooth movement of the screen into the water and into the proper position. Despite some misgivings, everything went well.

The boaters ensured that the bottom screen remained correctly in place as it slowly sank to the bottom of the lake (right). The installation went surprisingly well considering that the bottom screen was unwieldy. However, without the efforts of many neighbors, it would have been extremely difficult for this screen to have been installed. Installing this screen is a good example of home owners working cooperatively to manage aquatic weeds around a dock.

Find out how you can construct and install a bottom screen!

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