Here's the response from CAP.LA:

"The tool we used for the testing is great as a screener for potential metals and very good at testing for lead. Our recommendation is not that any expensive remediation happen right now, but that you get results using a more sensitive tool before taking any drastic steps. Following general safety practices like making sure you wash your hands, taking off shoes when you come inside, etc. is always good, but I wouldn’t recommend investing in anything major until you have results of additional testing. If you haven’t checked it out already, the Soil Information Sheet that’s available on out website would be a good source of information as well.

Hope that helps a bit,"

That does seem like a high amount of cobalt, but cobalt is not really too toxic or extremely poisonous. I wouldn't be too worried, so long as no one is eating the soil.

It's possible the cobalt came from natural sources and became freed, either from heating of certain hard minerals in the soil, or from ash from vegetation. It's also possible there may have been cobalt containing batteries that released cobalt in the intense heat of the fire, likely from electric vehicles (lithium batteries burn with a very hot intense flame and often contain cobalt alloy cathodes).

While above recommended levels, 71 mg/kg is not outrageously high. You can reduce levels by bioremediation (applying a layer of active compost) or by phytoremediation (planting something like sunflowers, that will pull the cobalt from the soil).

Thanks all !

And sorry so late in seeing this - I thought nobody was answering, since I didn't receive any notifications 🤔

She might want to contact one of the soil remediation companies which are working in Southern California at this time. I know people want to be safe if kids play in the yard or they want to grow plants for food.