4. Relevant Provisions of Rule 20

SCE's Tariff Rule 20 governs the conversion of overhead electric facilities to underground facilities. The tariff follows an underground conversion policy established by this Commission in 1967 in D.73078, 67 CPUC 490. That policy, little changed in subsequent years, encourages conversion statewide by having utilities, through rates, share some of the costs of conversion.

Rule 20.A applies to cities and counties and requires SCE to pay the costs of conversion, within specified limits, for projects deemed to be in the public interest. Rule 20.B applies to required conversion along public streets and roads by applicants other than cities and counties, with applicants bearing much of the cost. Rule 20.C applies to conversions by applicants not covered by 20.A or 20.B, with applicants paying all of the cost less net salvage value and depreciation of the replaced overhead facilities.

Rule 20.B applies to the conversion at issue here. In relevant part, it states:

"In circumstances other than those covered by A above, SCE will replace its existing overhead electric facilities with underground electric facilities along public streets and roads or other locations mutually agreed upon when requested by an applicant or applicants when all of the following conditions are met:

"2. The applicant has:

"c. Paid a nonrefundable sum equal to the excess, if any, of the estimated costs, including transformers, meters, and services, of completing the underground system and building a new equivalent overhead system.

"3. The area to be undergrounded includes both sides of a street for at least one block or 600 feet, whichever is the lesser, and all existing overhead communication and electric distribution facilities within the area will be removed."