The owner or owners of real property abutting an underground project or conversion area shall be responsible, at his or their expense, for converting to such underground service within 90 days after the date of the mailing or service of the notice as set forth in this chapter. Time in consummating such connection and disconnection of overhead service is of the essence and such notice to the property owner or occupant of the affected premises may be mailed, postage prepaid, or delivered in person. All of such conversion of electric and communication facilities to underground facilities may be undertaken by local improvement districts, or as otherwise permitted by law, and as further authorized by RCW 35.96.030 and 35.96.040. [Ord. 1758 § 2, 1976; Code 1970 § 12.34.020.]