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Aquatic Weed and Debris Control
Nuisance growths of aquatic weeds and algae have been problematic from the earliest years of lagoon operation. Left unchecked, nuisance growth can have a severe impact on aesthetic and recreational benefits, as well as water quality in the worst of conditions. Nuisance plant growth is largely a consequence of lagoon design. Shallow slopes, a shallow depth, and a loss of natural tidal action all contribute to promoting conditions favorable for nuisance growth.

The City practices an integrated approach to aquatic plant management. This means that a variety of control methods are used in order to avoid complete dependence on and minimize use of aquatic pesticides. Control methods include maximizing of water exchange to promote estuarine conditions; conducting pollution prevention efforts in the watershed to minimize introduction of nutrients into the lagoon; employing mechanical harvesting to control weed growth and remove the nutrient-rich biomass from the lagoon; and using action levels for herbicide application. Herbicide applications are spot applied whenever possible, and are applied during optimal stages of growth to maximize effectiveness. Learn more about the concept of integrated pest management.

The City hires a professional service to monitor and manage nuisance plant growth and debris. Tasks include visual monitoring of plant growth, mechanical harvesting, herbicide application, and trash and debris cleanup. Trash and debris find their way into the lagoon by way of O’Neill Slough, the upland creeks, channels, and storm drain inlets, and lagoon users. These materials, along with the weed biomass from the harvesting operation, are removed for the lagoon and disposed or recycled.

San Mateo City Hall – 330 West 20th Avenue, San Mateo, CA 94403

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