Lake Union Milfoil Removal Services

Lake Union milfoil removal for houseboats, marinas, and waterfront properties in the heart of Seattle

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(206) 395-8339

Why Lake Union Has a Milfoil Problem

Lake Union milfoil removal is a growing need for Seattle waterfront property owners as Eurasian watermilfoil (Myriophyllum spicatum) continues to spread through the lake’s 580 acres of urban shoreline. Connected directly to Lake Washington through the Montlake Cut and Lake Washington Ship Canal, Lake Union receives a constant influx of milfoil fragments from boat traffic moving between the two lakes, creating an ongoing reinfestation cycle that affects houseboats, marinas, and commercial waterfront properties.

Lake Union milfoil removal along a Seattle houseboat shoreline

Houseboat & Residential Lake Union Milfoil Removal

We clear Eurasian watermilfoil from around private houseboat moorages, dock floats, and residential shorelines on Lake Union. Most houseboat jobs are completed in a single day, with no damage to flotation systems, utility connections, or surrounding native vegetation.

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Marina & Commercial Lake Union Milfoil Removal

Large-scale Lake Union milfoil removal for marinas, yacht clubs, commercial waterfronts, and houseboat moorage operators. We coordinate with the City of Seattle, WDFW, and the Department of Ecology for any required permits and scale our equipment to match multi-slip operations.

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Our Lake Union Milfoil Removal Process

Free Assessment

We visit your Lake Union property, measure the affected area around your houseboat or dock, identify the milfoil density, and provide a clear quote with no obligation.

Removal Day

We arrive with the WaterShark harvester and hand tools, cutting milfoil at the root crown and extracting plant material before it can fragment and reroot. Most residential jobs are completed in one day.

Haul & Compost

All removed milfoil is hauled off-site for eco-friendly composting, never left to drift into neighboring moorages or decompose in the lake.

Why Lake Union Milfoil Removal Matters

Lake Union milfoil removal presents unique challenges that don’t exist on Lake Washington or Lake Sammamish. The lake’s heavy boat traffic, including seaplane operations, commercial tour boats, and the constant pass-through between Puget Sound and Lake Washington, means milfoil fragments are continuously introduced and redistributed. A single fragment broken off by a propeller can drift, sink, and root into a new dense mat in a matter of weeks.

For houseboat owners, untreated milfoil can wrap around utility lines, foul flotation systems, and create constant maintenance headaches. For marinas, dense milfoil mats in slips reduce boat access, damage propellers, and frustrate tenants. The cost of letting milfoil establish is almost always higher than the cost of regular Lake Union milfoil removal, both in equipment repair bills and in the labor required to clear a fully established infestation.

Because Lake Union is a state-regulated waterbody within Seattle city limits, working with a licensed and insured contractor matters. Milfoil Mercenaries is fully licensed and $2M insured, and we coordinate with the City of Seattle, WDFW, and the Department of Ecology when permits are required. For background on aquatic plant management in Washington, see the Washington Department of Ecology aquatic plants program.

Lake Union Neighborhoods We Serve

Lake Union sits at the geographic heart of Seattle, surrounded entirely by city neighborhoods. We provide Lake Union milfoil removal services along the entire shoreline:

  • South Lake Union: Office and commercial waterfronts, restaurant moorages, and the south-end park areas
  • Westlake: The Westlake houseboat communities, marinas, and west shore residential moorages
  • Eastlake: Eastlake houseboat communities, marinas, and east shore residential properties
  • Fremont: North-end shoreline approaching the Fremont Cut and Ship Canal
  • Portage Bay: Connected waters between Lake Union and the Montlake Cut, including the University of Washington shoreline
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Lake Union Milfoil Removal FAQ

Most Lake Union property owners schedule milfoil removal between late May and early September, when the plant is actively growing and easiest to identify and extract. Early-season removal (May to June) tends to produce the longest-lasting results because it’s done before milfoil reaches peak density and before fragmentation from summer boat traffic accelerates.

Yes. Our crew is experienced working around houseboat flotation systems, utility lines, and dock floats. The WaterShark harvester is designed for close-quarters work, and our hand tools allow precise removal in tight spaces between floats and pilings. We’ve completed Lake Union milfoil removal jobs around every common houseboat configuration in Seattle.

Most Lake Union waterfronts benefit from annual milfoil removal. Because the lake has constant boat traffic moving milfoil fragments between Lake Washington and Puget Sound, even a thorough clearing will see regrowth the following season. Annual maintenance keeps your moorage open and prevents milfoil from reaching unmanageable density.

Most residential mechanical milfoil removal around a private houseboat or dock falls under the homeowner maintenance exemption and doesn’t require a permit. Larger commercial jobs, marina-wide clearings, or any chemical treatment may require coordination with the City of Seattle, WDFW, or the Department of Ecology. We handle permit research as part of every commercial project.

Chemical herbicide treatments kill milfoil in place and leave the dead plant material to decompose in the water, which depletes oxygen, can harm fish populations, and often requires Department of Ecology permits. Our mechanical Lake Union milfoil removal physically extracts the plants and hauls them off-site for composting, with no chemicals entering the lake.

Ready to Clear Milfoil from Your Lake Union Property?

Get a free, no-obligation quote. Serving houseboats, marinas, and waterfront properties across South Lake Union, Westlake, Eastlake, and Fremont.

Get Your Free Quote
(206) 395-8339
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