The following is a post on Ukiah Waste Solutions Facebook page:
DO NOT PLACE HOT/WARM ASHES in any of your curbside carts. Not only can this melt the carts (as shown below) it can cause a fire in the collection truck. Please allow your fireplace ashes to cool for 48 hours before disposing of them in your GARBAGE cart.
Ukiah Waste Solutions provides the following infographic for tips and tricks to properly dispose of ashes: