Community of Harbor Bay Isle Lagoon System

The Harbor Bay Isle lagoon is located on the Bay Farm Island peninsula in Alameda, on the east bay shoreline north of the Oakland Metropolitan Airport. It forms the major component of the Harbor Bay Isle Master Plan Community, providing open space, wildlife habitat, aesthetic and recreational enjoyment for the residents of the Community. The lagoon also accepts storm water drainage from the adjacent developed areas.

Extending from San Francisco Bay at the west end of the lagoon system to San Leandro channel at the north, the lagoon is a narrow river like waterway nearly 2.5 miles long. The basic operation of the Lagoon is dependent upon the normal San Francisco Bay tidal action which through a series of sluice gates at each end of the lagoon, provide a degree of flushing from west to north while maintaining a calibrated water level 2 to 4 inches below the top of curb. During normal operation, the anticipated average water retention time is approximately four days.

The Community Water Quality Division is dedicated in providing a safe and positive environment for our residents to enjoy. Please take a moment to review this NEW, dedicated Lagoon informational web page intended to provide information to our Harbor Bay Isle residents regarding our Best Management Practice for Lagoon water quality and establish an avenue of information readily available for homeowners.

Who to Contact

Please direct any general questions or issues to Director of Maintenance, Joe Landaeta, 510-865-3363 ext. 350.

Lagoon Water Levels

The Community of Harbor Bay Isle works with The City of Alameda Department of Public Works to flush the lagoon system based on the extreme low tides. This process helps cool down the water and elevate the oxygen levels in the water.

2023 Community of Harbor Bay Isle Lagoon Lowering Schedule
The Community of Harbor Bay Isle has coordinated with the City of Alameda to lower both lagoon systems on the following dates:

Scheduled Dates Alternate Rain Dates
April 10 – 14, 2023 April 24 – 28, 2023
October 2 – 6, 2023 October 16 – 20, 2023

Please direct any questions regarding the lagoon to our Director of Maintenance, or  510-865-3363 ext. 350.


To check the current tide predictions, the Community recommends visiting the following sites:

Aquatic Plant Management

by Joe Landaeta

As many homeowners have noticed, the Harbor Bay Isle lagoon system has once again been visited by Algae and Widgeon grass.

WIDGEON GRASS (Ruppia maritima): This plants leaves are thread like, narrow, extending from an extensive buried root system. Commonly found in shallow, brackish or alkaline waters.

Found mainly along coastal areas, but scattered into many inland Midwestern lakes, the plant is prime waterfowl food and desirable in some locations. The Community utilizes several methods of control for this and other invasive plants such as biological, mechanical, cultural and chemical in our Best Management Practices. This year’s record rainfall allowed excessive nutrients runoff into our lagoon soil profile and created the perfect environment for the submersed plant to grow at a rapid pace. This cycle occurs about every three years depending on the environmental conditions and the phenology of the plant.


Also known as “Moss” because it forms mats upon the water’s surface. Filamentous algae usually begin its growth cycle along the edges of bottom of the lagoon and “Mushrooms” to the surface buoyed by oxygen it has produced. Individual filaments are a series of cells joined end to end which give the thread-like appearance. They also form fur-like growths on bottom logs, rocks and even on the back of turtles. The texture of these growths may be slimy, cottony, or coarse.

Common names such as frog spittle and water net have been given to a few forms.


Following lagoon water quality observations, staff completed a successful introduction of biological controls in early February for algae suppression. The lagoon lowering in April will allow staff to service maintenance pads, storm drains, docks, and shorelines.

Solitude Lake Management has implemented targeted suppression operations to eradicate both algae and widgeon grass.

For additional Lagoon Water Quality information please contact the Director of Maintenance, Joe Landaeta, 510-865-3363 ext. 350.

Aquatic News

Runoff of Phosphorus and Nitrogen from Homeowner and Community Landscapes

By Joe Landaeta

Phosphorous is not an element that most Homeowners or landscape professionals would associate with water quality problems. Certainly, pesticides and nitrates easily come in mind when considering possible contamination of surface water. However, recognizing water quality problems and awareness that there are extremely high maintenance levels for lawns and landscaped areas within Harbor Bay Isle has led to concern about phosphorus and nitrogen levels leaching into our lagoon system.

Turfgrass grown mostly for visual, aesthetic and lounging on uses, is found in front and to the rear of many residences on the Island. Healthy, vigorous and attractive turfgrass is maintained by mowing, irrigating and fertilizing. Fertilizer that is applied excessively or inappropriately, can runoff or leach through the sandy soils on the island, and end up in the lagoon system where it may contribute to water pollution, algae and undesirable aquatic plant life.

Fertilizer replaces nutrients removed from the soil by growing plants. The amount of fertilizer applied should not exceed established levels, or turfgrass quality can decline.
Timing and methods of application should match the turfs’ needs and uptake abilities, taking into consideration soil and ambient temperatures, wind, rain and irrigation.

Soils on the island are coarse textured (sand), porous, and usually have low levels of organic matter like silt or clay. These are usually nutrient poor soils. However, the physical conditions are good for turfgrass growth when drainage is good and adequate supplemental nutrients are provided. Sandy soils that drain well are likely to leach certain nutrients such as nitrogen into the lagoon, when they are irrigated or when rainfall occurs.

Home maintenance tips for a cleaner lagoon system.
Make sure your gardener collects yard waste for composting and does not blow or rake leaves into the street or gutter. If you contract with a lawn maintenance service, limit fertilizer applications to twice a year (fall and spring), and limit application of actual nitrogen on cool season grasses to 4 pounds per 1,000 square feet. Chemical and other pesticides should not be necessary on lawn that is appropriately watered, mowed, thatched, and aerated. Never apply chemicals when rain fall is forecast

For additional information please contact the Director of Maintenance, Joe Landaeta, 510-865-3363 ext. 350.