(1) the utility shall install underground without contribution from the applicant an amount of feeder facilities from the boundary line of the residential subdivision equal to 25 feet per dwelling unit or 200 feet, whichever is greater, except as may be required under paragraph (3) of this subdivision; in no event will the utility be required to provide more than 500 feet without contribution by the applicant;

(2) the utility may, at its discretion and expense, install underground additional portions of connecting feeder facilities; and

(3) where any part of a feeder facility in excess of that required by section 604.4(a)(1) of this Part is to be placed overhead, the applicant must submit a written application to the utility at least 75 days prior to the projected commencement of construction of the feeder facility and the utility must report such projected construction to the commission no later than 45 days before such construction is commenced, the commission reserving the right to require the underground installation of particular facilities on the basis of the relevant economic, engineering or environmental factors.