Delivering Natural Gas
PG&E’s integrated natural gas transportation, storage and distribution system supplies natural gas to approximately 4.3 million customers in northern and central California via 6,000 miles of transmission pipelines, approximately 43,000 miles of distribution lines and three underground storage facilities.
PG&E’s gas system is supplied by natural gas fields in California and through interconnections with interstate pipelines that connect to all the major natural gas areas in western North America. The company’s total volume of natural gas throughput during 2010 was approximately 842 billion cubic feet (Bcf).
Pipeline Safety Inspection and Testing
Following the San Bruno tragedy, PG&E is examining every aspect of our gas operations and pipeline system. We’ve acknowledged that we need to make major improvements to deliver the performance our customers rightly expect—and that we expect from ourselves. A more detailed explanation of steps PG&E has taken and continues to take as we strengthen our gas operations is available in this section.
PG&E monitors the system status on a 24-hour basis and regularly conducts leak inspections, surveys and patrols of our system. Any issue identified as a threat to public safety is immediately addressed.
To track and adjust gas pressure as necessary as it moves through the pipeline system, PG&E uses regulator stations, which are found along all of our gas transmission lines. The regulator stations are designed to maintain a downstream pressure that does not exceed the maximum allowable operating pressure, or MAOP. After the gas passes through a regulator station, it reaches a secondary safety measure of either a relief valve or a monitor. In case the regulator malfunctions, the secondary monitor is designed to reduce pressure quickly if it exceeds MAOP by a certain margin, typically below 10 percent.
After the gas proceeds past the regulator station, pressure decreases downstream along the pipe as it travels toward the distribution system, which carries the gas to homes and businesses.
Improving Gas System Reliability
In 2010, the company completed an accelerated effort to survey its entire gas distribution system over an 18-month period, a process that normally takes five years, in addition to our routine program to survey gas services. We also surveyed gas services in Eureka, California, after an earthquake in the area. Together, PG&E surveyed more than 882,400 gas services on our distribution system in 2010.
In the wake of the tragic San Bruno accident, PG&E also completed a massive re-inspection of our gas transmission system, totaling approximately 5,700 miles, in 2010. It is important to note that PG&E routinely surveys its natural gas pipelines for leaks. All Grade 1 leaks are repaired immediately.
Investments in Gas Storage
To meet the year-round needs of our gas customers, PG&E compresses and stores gas during summer months. This gas is then used during winter months to meet gas demands on the coldest days. We currently operate three gas storage facilities located across our service area, the largest of which has a storage capacity of 134 Bcf, making it one of the largest storage facilities in the western United States.
To enhance our ability to meet peak demand, PG&E has also jointly developed a new underground storage field near Fresno with Gill Ranch Storage, LLC, with the first phase of 20 Bcf capacity becoming operational in October 2010. Through PG&E’s ClimateSmart™ program, Gill Ranch Storage is offsetting the greenhouse gas emissions associated with the project’s energy consumption. Additionally, during project construction the developer minimized environmental impacts by using horizontal drills to avoid impacts to sensitive water sources and by requiring low-emission engines and limiting idling time for equipment. The project also will reduce air emissions by using electric motors to power the storage system’s five compressors and by offering employee shuttles to reduce vehicle traffic to the site.
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