
Quoting
Driscoll v. City of Los Angeles (1967) 67 Cal.2d 297, at p. 305, 61 Cal. Rptr. 661, 431 P.2d 245.
Generally speaking, four elements must be present in order to apply the doctrine of equitable estoppel: (1) the party to be estopped must be apprised of the facts; (2) he must intend that his conduct shall be acted upon, or must so act that the party asserting the estoppel had a right to believe it was so intended; (3) the other party must be ignorant of the true state of facts; and (4) he must rely upon the conduct to his injury.