Lake Temescal reopens after toxic algae bloom. Floating islands in its future

- With the summer almost over for most Oakland students who have to return to school in a few weeks, Lake Temescal will reopen on Saturday.

The lake, considered a jewel that sits above the Rockridge and Temescal neighborhoods, has been closed for most of the summer because of toxic algae blooms – a situation that has played out for the last four summers.

Historically, the lake has been a summer go-to spot, densely populated parents and toddlers, teens and couples who lay on the sandy beaches, swim in the water and even enroll in lifeguard camp, which has been shuttered for the last couple years.

The larger question remains, will it ever be healthy enough to recreate those summertime scenes again?

“That’s a complex question,” East Bay Regional Park District Chief of Stewardship Matt Graul told KTVU on Thursday. “There are a lot of factors here, from old reservoirs to urban development causing a lot of nutrient runoff. We think we have solutions that can work. But we’re going to have to wait two or three years to really know for sure if we have a long-term solution.”

Park staff are considering a range of options, from floating islands to dredging, to restore it in the long-term future.

Toxic algae blooms, or cynobacteria, is an issue that’s plaguing water bodies across the country. The biggest reasons? Toxic blooms are a worldwide problem and are exacerbated by sediment and nutrient build-up, pollution and aging reservoirs, along with warm temperatures because of drought and global warming.

Not only does cyanobacteria cause dogs to die, but humans can experience vomiting, diarrhea, liver inflammation, hemorrhaging, kidney damage, acute dermatitis and potential tumor growth if they come in contact with it.

Of the nine lakes in the park district, eight have had toxic blooms – Lake Temescal has suffered the worst, as it has been closed on and off since 2014. At this point, the park district estimates it has spent about $200,000 on fixing the problem and Graul said he it's unknown how much it will cost to restore the lake back to healthy swimming levels in the future.

Over the summer, park staff “spot treated” cyanobacteria the lake with aluminum sulfate.

But a long-term solution is needed to prevent future blooms. Some of the recommended solutions include:

1. Using a “a phoslock treatment” comprised of an Australian-rare earth element lanthanum with benthic clay. Phoslock binds with phosphorus, a nutrient required by cyanobacteria. Last year the park district used half a recommended dose of this element at a cost of $100,000 to see if it would be effective. The treatment cleared up the water and the thick cyanobacteria blooms did not form as in the previous years, but cyanobacteria still grew and toxins were produced.


2. Creating floating islands, which absorb lake nutrients, is also being considered. Islands require some maintenance but are relatively inexpensive. A group at UC Berkeley is interested in helping to create and maintain these islands. Experts say that you would need a lot of islands to make this effective. The district is open to trying out some of these islands, but they do not expect them to be the only solution.


3. Dredging the sediment in the lake and creating wetlands could cost as much as $5 million. Dredging rids the nutrient-rich sediment and establishes a deeper, more stratified body of water that would be less susceptible to cyanobacteria blooms. The district is funding a study to look into actual costs and wetland designs.

4. The  most realistic solution for the park district will come in the form of aluminum sulfate, MacLean said, because it’s effective and costs less than phoslock. This fall, the park district plans an alum treatment which binds up phosphorus to reduce the nutrients available for cyanobacteria, if the regimen is approved by the San Francisco Bay Regional Water Control Board. “Alum,” as it’s called, is a nontoxic material commonly used in water treatment plants to clarify drinking water. In lakes, alum is used to reduce the amount of the nutrient phosphorus in the water, thereby limiting the availability of this nutrient for algae production.

But according to Lake Savers, a site devoted to renewing lakes naturally, alum treatments do nothing to reduce nitrogen and “locked” phosphorous is re-released into the water.

MacLean acknowledged that this treatment isn’t a “complete fix. That’s why you ultimately have to dredge.”

But dredging brings with it other problems, he said. Not only do early estimates cost in the millions, but MacLean said, but “dredging won’t last forever either. You’d have to continue dredging every so often.”

As for what will actually fix the lake, Graul said that he and his team are still investigating the best options.

“We think we have the solutions,” he said. “We don’t know if these problems will go away completely, but we are trying to figure out how to better manage it.” 

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