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OAKLAND, Calif. (KTVU) - Environmental engineers were back for the second time this week, spraying Oakland's Lake Temescal.
They are hoping this time the chemicals will kill off all of the toxic algae bloom that has forced the lake to be off limits to swimmers.
"It's actually a bacteria and we want to make sure it's not around," said Hal MacLean of the East Bay Regional Park District.
The toxin is in a bloom of what's called blue-green algae. It was discovered June 30th when routine water quality tests were well above the health department's safe limit standards.
Since swallowing the water could cause liver damage, authorities immediately closed the lake.
Engineers treated the lake with a hydrogen peroxide solution earlier in the week. They say it killed off most of the toxins, but not all. So they were back Friday.
"They had us treat in very specific areas where they saw it start to come back. What we did today was go to those areas, hit them so it doesn't become a full bloom again," said Ira Kersh, an Environmental Services Manager.
The combination of dreary weather and the closed off lake has kept people away.
The Junior Lifeguard Program was still operating, but only a fraction the campers that originally signed up, have been showing up. Those that do come have been confined to land.
The blue-green algae did appear last year and authorities believe the drought and warm water temperatures may be the cause.
"We need to get our confidence level up, work with Alameda County Environmental Health to make sure we are both confident we don't have these toxins in the lake," said McLean.
The samples will be tested early next week. If all goes well Lake Temescal could be reopened by next weekend.