A public entity, like the city of Costa Mesa, is liable for injury caused by a dangerous condition of its property “if the plaintiff establishes that the property was in a dangerous condition at the time of the injury, that the injury was proximately caused by the dangerous condition, that the dangerous condition created a reasonably foreseeable risk of the kind of injury which was incurred, and that either: (a) A negligent or wrongful act or omission of an employee of the public entity within the scope of his employment created the dangerous condition; or (b) The public entity had actual or constructive notice of the dangerous condition (under Section 835.2) a sufficient time prior to the injury to have taken measures to protect against the dangerous condition.”

https://www.advocatemagazine.com/article/2016-november/proving-a-condition-of-public-property-is-dangerous