Harbor Bay Lagoons Will be Lowered Monday

The draining of the Harbor Bay lagoons, originally scheduled for July 11 but cancelled because of extremely high temperatures, is set to go forward on Monday, August 8.  

Joseph Landaeta, director of maintenance for the Community of Harbor Bay Isle, said the lagoons are lowered periodically to allow homeowners to inspect and repair their private docks. It is done only when oxygen levels in the lagoons' water remain adequate to support the fish that live there. 

“When the oxygen gets below five parts per million,” he explained, “we risk fish dying.” 

Heat, Landaeta said, also plays a role in oxygen levels in the water. In the event the ambient temperature should rise above 70 degrees Fahrenheit, for example, the water-lowering process could potentially have to be postponed yet again, according to a notification card issued to homeowners.

Samples are taken from the lagoons year-round on Mondays, Wednesdays and Fridays to determine water quality. 

Landaeta said his department works in concert with the city of Alameda's Public Works Department, which handles the actual flow of the water in and out of the lagoons from San Francisco Bay.   

Assuming it is not too hot and the oxygen levels remain adequate, on Monday city staff will flip a switch during low tide, opening up two automatic gates and allowing the lagoon water to flow into the bay. 

On Friday, August 12, during high tide when the lagoon fills back up, the gates will be closed again to contain the water. During that process city staff will monitor a device which calibrates the water level of the lagoons, ensuring it is back to normal. 

While the lagoons are drained people in the area may smell a strong odor of hydrogen sulfide from exposed decomposing algae or pond weed.

During the week when the water is lowered, the 60 storm drains that empty into the lagoons will be cleaned out, bridges will be checked, and residents may inspect and repair the exposed pylons of their private docks and curb walls. It will also give residents an opportunity to clean up along the edge of the lagoon by their homes.

“Some of these docks are 30 years old,” said Landaeta, “and they are reaching a point where they are needing repairs.” Homeowners pay for their own docks' repairs and must have their construction plans approved by the Community of Harbor Bay Isle architectural standards manager.

Water fowl and aquatic creatures will not be adversely impacted by the lagoon lowering, according to Landaeta. “I’ve been here 30 years and that has never been a problem,” he said, noting that the level of water allowed to remain in the lagoon after lowering is adequate to support the wildlife there.

As for concern about the lagoons overflowing in the event of a rise in sea level or other changing conditions, Landaeta said the lagoon system is designed to handle a 100-year-flood. There is an auxiliary pump available, which he said has occasionally been used, which can pump water out of the lagoon in the event of a particularly high tide or excessive rain.

He said the city takes pro-active measures if rain is forecast. “They monitor the weather,” he said, “and if they anticipate two inches of rain, for example, then they might lower the lagoon by four inches in advance.”