Acknowledging that natural gas transmission pipeline pressures will remain at reduced levels in San Francisco and the peninsula area to its south this winter, Pacific Gas and Electric Co. (PG&E) on Wednesday will kick off a targeted advertising and bill discount incentive campaign to get customers in those areas to reduce their energy consumption in December.

State regulators and the San Francisco-based combination utility have been concerned that the lower pressures on three transmission lines running through the San Bruno area, site of the Sept. 9 fatal gas line rupture and fire, could cause noncore customers to be curtailed (see Daily GPI, Oct. 29). However, with various mitigation measures, including the shareholder-funded added conservation incentive program, PG&E thinks the curtailments may be averted.

"Any customer who can save more gas compared to their December use the previous two years will get a $25 pre-paid debit card as a means of thanking them for making a difference at an important time," a PG&E spokesperson told NGI late Tuesday. The program will be confined to residential customers in San Francisco and San Mateo Counties; noncore customers threatened with potential curtailments are already taking steps to lessen their usage.

At stake is a collective noncore gas load of 200-225 MMcf/d, representing 25% of PG&E's overall gas demand in San Francisco and San Mateo Counties, the utility spokesperson said.

In January and February, PG&E will go back to its regular, companywide winter gas savings programs offering 10% bill credits for customers who can lower the amounts of energy they save in the two full winter months compared to usage in those months the previous year.

In the immediate aftermath of the San Bruno pipeline tragedy, PG&E lowered pressures in the transmission pipelines running through the peninsula and subsequently, the pressures were lowered further at the direction of the California Public Utilities Commission (CPUC), and they remain at the 300 psi level.

High-pressure gas pipelines typically operate at pressures between 100 and 1,040 psig (pounds per square inch gauge), with pressures varying with the size and physical characteristics of the pipelines. Federal limits for transmission pipelines such as Line 132 are set at 400 psi, and PG&E has used 375 psi as its operating limit, but with the lower pressure the maximum volumes of gas are reduced also, so when winter peak-demand hits the line is limited in how much more gas it carry.

PG&E said the utility has been working with the CPUC to take various steps to mitigate the lower pressure limitations. "We're continuing to serve our customers in San Francisco and on the peninsula at the lower operating pressures. We will not raise the pressure on any of the lines until our assessments are complete and we have discussed all of the ramifications of those reviews with the CPUC and local government officials."

Through adding valves and other modifications to the three pipelines to increase their "operational flexibility," the spokesperson said PG&E is hoping to stave off the need for curtailments. "We've offered interties and installed additional isolation valves, pressure regulators and other devices."

The utility is feeling more confident going into December, the spokesperson said, because for the past seven or eight days California has been experiencing colder-than-normal conditions, and so far PG&E has not had to resort to any curtailments anywhere.

While gas curtailments remain a possibility for PG&E's largest customers in San Francisco and the peninsula region to the south, a separate electricity milestone in the Bay Area Monday has helped ease that threat (see Daily GPI, Dec. 1).

©Copyright 2010 Intelligence Press Inc. All rights reserved. The preceding news report may not be republished or redistributed, in whole or in part, in any form, without prior written consent of Intelligence Press, Inc.