How to build a barrier that can prevent aquatic invasive species from growing near your dock or property.
The Inland Northwest is known for its beautiful waterways.
For many who live here, playing on the water is a favorite pastime.
Nothing ruins the fun on the water quicker, however, than invasive aquatic weeds. Unlike natural plants that are important to a lake’s ecosystem, invasive aquatic weeds impact the health of our lakes and make it difficult to play in the water.
They reduce available habitat for wildlife. And because they are denser than native plants, they can entangle fishing lines and boat propellers.
Invasive aquatic weeds are a problem, but waterfront property owners can help fight back.
One way is by installing a bottom barrier along their docks.
A bottom barrier is a tool installed underwater to block sunlight from reaching the lake bottom.
This prevents weeds from growing in the first place.
Building a bottom barrier for your shoreline only requires a few, fairly inexpensive materials, including geotextile and four, 10-foot sections of 1-inch PVC pipe.
To connect the corners of your frame, use joints. They’ll let water fill the frame to help it sink.
Or, for areas with strong currents, use elbow joints and fill the frame with heavy sand to help act as an anchor.
When your 10 by 10-foot frame is assembled, the 12-foot long geotextile material will have enough length to wrap around the frame to sew a sleeve that will secure the pipe frame.
Slip it onto the frame before the last side is assembled. Geotextile is a special material that lets bottom gases penetrate.
Tarps or other materials can trap gases which may cause your barrier to float away. Plus, they quickly deteriorate and pollute the lake.
Once you have attached the geotextile to your assembly, your bottom barrier is ready to be submerged to block weed growth.
For a complete supply list and instructions, visit myavista.com/shorelinehealth
How to Build and Install a Bottom Barrier
Building a bottom barrier for your shoreline only requires a few, fairly inexpensive materials, including geotextile, 40-feet of 1-inch PVC pipe, four PVC connectors and glue.
- To connect the corners of your frame, use PVC slip Tee joints but do not bond them with glue yet. Slip Tee joints let water fill the frame to help it sink.
- Or, for areas with strong currents, use 90 degree Elbow joints and fill the frame with sand that acts as an anchor. With your PVC frame now assembled, the 12-foot long geotextile material has enough length to wrap around opposite sides of the frame. Sew a sleeve on each site to secure it to the PVC frame. Slide sleeves onto the PVC frame. Now, the slip tee joints and PVC pipe can be glued together.
- Geotextile is much more durable than a tarp, and it lets bottom gases penetrate. Tarps or other materials can trap gases which may cause your barrier to float away and pollute the lake. Your bottom barrier is then ready to be submerged to block weed growth.
- The ideal time for placing a bottom barrier on the lake bottom is in May prior to plant growth. Annually removing bottom barriers from the lake is important because it allows sediment that has settled on the geotextile fabric to be removed, eliminating the likelihood of aquatic plants taking root there, and it prolongs the life expectancy of the bottom barrier. If the bottom barrier is removed around the end of July, the area covered should be free of aquatic plants for the rest of the summer.
- 40 feet of 1-inch PVC pipe in 10-foot lengths.
- Four 1-inch PVC slip Tee joints for the corners (allows water to fill PVC pipes). Or, in areas with current that may move the bottom barrier, use 90 degree Elbow joints and fill PVC pipe with sand.
- Standard PVC pipe glue.
- 12-feet x 10-feet of Geotextile (such as Dupont SF40 fabric)
Proper installation techniques are important to ensure the success of your bottom barrier as well as to reduce its impact on the lake. For example using improper materials such as tarps may trap methane gases, if not secured the tarps can float away becoming ineffective. Improperly maintained bottom barriers may deteriorate and pollute the lake.
Visit Washington Department of Fish and Wildlife’s Rules for Aquatic Plant Removal and Control (PDF) for more information. Idaho Department of Lands regulates the use of bottom barriers in Idaho. If you have any questions, view the contact information for the agency.
Contact Restoration Biologist Robert Stephens at (509) 495-8340 to learn how Avista can help.
Creating a more natural shoreline is good for your property and the health of the lake.
Here in the Inland Northwest, we love clean water, abundant wildlife, and access to recreation on our lakes and rivers.
That’s why all of us need to be good stewards of our waterways—beginning at the shoreline.
Waterfront property owners play an important role in shoreline preservation.
They can help…by maintaining or creating natural shorelines.
Artificial bulkheads and seawalls along shorelines can cause damage.
If waves from wind and boats pass over these shoreline walls, the resulting energy can scoop out soil and sand. This erosion may undercut the wall’s stability, as well.
This wave energy can adversely affect properties down the shore, too, washing away shoreline sediments.
That’s why natural shorelines are a better solution. Natural shorelines slope gradually instead of dropping off at the water’s edge. The gentle slope helps dissipate wave energy.
It also makes life easier for aquatic life, such as turtles, frogs and other animals, when they need to exit the water to rest, feed and nest on land.
A natural slope encourages the growth of native plants, too, which in turn helps to preserve the shoreline.
Native plants have extensive root systems that anchor the soil in place, reducing the erosion caused by waves.
They also help maintain aquatic biodiversity by keeping invasive plant species, such as flowering rush and milfoil, from taking root in the water.
Native plants absorb nutrients and pollutants in surface water, too, ensuring the overall health of our waterways.
If you’re a waterfront property owner, contact us to learn more about creating a natural shoreline.
Contact Water Quality Specialist Monica Ott at (509) 495-4651 to learn how Avista can help.