Every site development permit shall expire and become null and void if the work authorized by such permit has not been commenced within one hundred eighty (180) days of the permit date, or is not completed by a date which shall be specified in the permit; except that the Director of the Community Development Department may, if the permittee presents satisfactory evidence that unusual difficulties have prevented work being commenced or completed within the specified time limits, grant a reasonable extension of time if written application is made before the expiration date of the permit.
(1987 Code § 18.50-18)