Officials say more than 900 gallons of a solution were recovered from storm drains.
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On October 17, Palo Alto resident Mike Hedlom took this video of the neon green liquid outside a Tesla research facility.
"I was pretty sure it was probably a coolant or a brake fluid, something along those lines but even so it wasn't what should be in the gutter," Hedlom said.
Hedlom reported it to the city.
The Office of Emergency Services said some kind of chemical used to cool the Tesla AI Supercomputer was released into a storm drain, the gutter and Matadero Creek.
It apparently happened due to a mistake while crews were draining the Tesla system.
The city says the solution does not pose a risk to life or health.
"It's not as bad as it could be, but I still didn't know what it was and we definitely don't want that in the creeks because everything here flows out into the bay," Hedlom said.
Last Tuesday, Cari Templeton heard from a neighbor wondering why work crews were cleaning up Matadero Creek. After inquiring with the city and Valley Water, Templeton said the next day, the city notified residents about the chemical spill - but this was five days after it was reported. Templeton is running for a Palo City Council seat.
"I think that should've happened sooner rather than later and I think it should've been proactively done by the city instead of as a result of people trying to investigate on their own," Templeton said.
On Friday, the city released this statement:
"In hindsight and with appreciation for the input received since, staff recognizes that we should have made public notifications sooner. We apologize for our delay in making notifications."
The city says in addition to cleanup, the cause is under investigation. Storage of sodium hydroxide requires a city permit which Tesla did not have.
We spoke to Lauren Weston, Executive Director of the environmental nonprofit organization, Acterra.
"We just want to make sure our communities are safe and corporations have an obligation to take care of our communities - they share our backyard, we need to know that they're doing their very best to keep our communities and planet safe - this shouldn't happen," Weston said.
The city say a final round of testing is underway, and results are expected to take at least a week.