PG&E shared the following responses to written questions from The Bakersfield Californian. PG&E spokesman Brian Swanson sent the responses.
Question: What kind of safety tests and inspections has PG&E performed on gas transmission lines in Kern County over the past five years?
Answer: PG&E has several transmission pipelines, including Distribution Feeder Main (DFM) pipelines in Kern County, the majority of which are in the Bakersfield area. They include transmission Lines 312, 319, 375, 376, 142N and 142S, as well as Lines 300A and 300B, which are the two major transmission pipelines bringing gas from the Southwest into California and up to the Bay Area.
PG&E has a comprehensive inspection and monitoring program to ensure the safety of its natural gas transmission pipeline system. PG&E regularly conducts patrols, leak surveys and cathodic protection (corrosion protection) system inspections for its natural gas pipelines. These tests are conducted on all transmission lines from the date the pipeline is initially installed. Any issues identified as a threat to public safety are immediately addressed. PG&E also performs integrity assessments of certain gas transmission pipelines in urban and suburban areas (which are identified as High Consequence Areas).
Patrols: PG&E performs regular patrolling of transmission pipelines to look for indications of pipeline leaks, missing pipeline markers, construction activity and other factors that may threaten the pipeline. Transmission lines are patrolled at least once every quarter. All of the transmission lines in Kern County have been patrolled numerous times over the past five years.
Leak Surveys: PG&E regularly conducts leak surveys of its natural gas transmission and distribution pipelines. After the San Bruno incident, PG&E performed additional ground leak surveys for its entire natural gas transmission system. Leak surveys are generally conducted by a leak surveyor walking above the pipeline with leak detection instruments. Transmission pipelines are surveyed for leaks either semi-annually or annually, depending on the pipeline. All of the transmission pipelines in the Bakersfield area have been surveyed for leaks at least once a year for the last five years, and twice in 2011.
Cathodic Protection System Inspections: PG&E utilizes an active cathodic protection (CP) system on its gas transmission and steel distribution pipelines to protect them against corrosion. PG&E inspects its CP systems every two months to ensure they are operating correctly.
Integrity Assessments: There are three federally approved methods to complete a transmission pipeline integrity management baseline assessment: In-Line Inspections (ILI), External Corrosion Direct Assessment (ECDA) and Pressure Testing. An In-Line Inspection involves a tool (commonly known as a “pig”) being inserted into the pipeline to identify any areas of concern, such as potential metal loss (corrosion) or geometric abnormalities (dents) in the pipeline. Excavations are performed in areas of concern as required by federal regulations. These integrity assessments are performed at least once every seven years on pipelines in High Consequence Areas (HCA). Some of the transmission lines in Kern County are in HCAs. PG&E will have completed its baseline assessments for all HCA segments by the end of next year.
In addition to this regularly scheduled work, PG&E currently is pressure testing approximately 150 miles of transmission line systemwide in 2011, and has proposed a plan to pressure test all transmission lines that have not previously been pressure tested. Ten of these pressure tests in 2011 are in Kern County on Lines 300A and 300B. Five tests have been successfully completed, and the pipeline sections are back in service. The other five tests either are in process now or are still in the planning and preparation phase.
One of these tests was the one near Bakersfield where the pipe recently failed. This section will require repairs and restesting before putting the pipe section back in service. To put things into perspective, that pipeline failed during a hydrostatic pressure test when the test pressure reached over 130 percent of the pipe’s maximum allowable operating pressure.
PG&E is reviewing many things to ensure the safety of its gas transmission pipeline system, including performing a validation of its maximum operating pressure for all of its transmission pipelines, including those in Kern County.
Q: On your website, it says the criteria for being identified for testing is lines that have no records or incomplete records or are just old. Why was line 300B being tested? Are records for that line incomplete?
A: This year beginning in April, PG&E started work to perform a hydrostatic pressure test on 150 miles of gas transmission lines. We are planning to complete most of these tests before the winter. These tests are part of PG&E’s aggressive action to improve the safety and reliability of our system. Going forward hydrostatic pressure tests will be part of PG&E’s regular integrity management program.
Most of the pressure tests we are conducting this year are on pipeline segments that are located in high consequence areas and don’t have a record of a previous pressure test. Even though this pipeline segment in Bakersfield is located in a remote area, it passes a farm building — which makes it a high consequence location.
Q: When was Line 300B installed?
Q: Pounds per square inch gauge, or PSIG, is a unit of measurement for the pressure a gas or liquid exerts on the walls of its container. How many pounds per square inch gauge were applied in the local pressure test?
A: We were ramping the test pressure up to 1,040 PSIG when the pipe failed at 998 PSIG.
Q: Can you tell us specifically where the ruptured line begins, its route, and where it ends?
A: Here is a map of PG&E gas transmission lines. Lines 300A and 300B travel near the Arizona border to our Milpitas Terminal in the Bay Area through west Bakersfield.
Q: Why was the pressure limiting station outside of Bakersfield out of commission Monday and when will it be back online again?
A: We have a regulating station for Line 142N, which is one of the two primary gas transmission lines serving Bakersfield. Line 142S is the other. It was taken out of service to complete a station rebuilding project that began last year.
Q: In layman’s terms, what does that station do?
A: A regulating station reduces gas pressure in a pipeline system.
Q: The fact that the local pipeline failed a test would seem to portend a safety issue. Are the communities where this line goes safe?
A: PG&E is conducting hydrostatic pressure tests throughout its service area to find any weaknesses that exist in our pipelines. We want to identify any weaknesses during a hydrostatic pressure test so that we can immediately repair, replace and retest the segment, and ensure that our natural gas transmission system is operating safely and reliably.
Since April, we’ve conducted more than 60 hydrostatic pressure tests on nearly 120 miles of pipeline throughout our service area. All of these tests have been successful and no weaknesses have been found prior to Monday’s test.
Hydrostatic pressure testing involves filling a section of pipe with water, pressurizing it to a much higher level than the pipe will ever operate with natural gas, then monitoring the pipe for at least eight hours. When a pipe successfully passes the testing pressure, then we have a significant margin of safety built into the operating pressure.
Pressure testing is just one of the many ways PG&E is taking aggressive action to test an inspect its gas transmission system. PG&E is overhauling its gas operations and we have new leadership in place with the mandate to make our operations and culture more focused on safety.
* We’ve improved our integrity management and risk assessment programs by increasing the number of tests and inspections we conduct on our gas system and by utilizing the latest tools and technologies to ensure its safe operation.
* We’re using high-definition cameras to inspect the internal conditions of some pipelines and we’re using high-tech devices called “smart pigs” that provide a detailed analysis of pipeline conditions.
* We are also modernizing our infrastructure by replacing older pipe with new pipe and automating hundreds of shut-off valves throughout our system. This year, we plan to automate 29 shut-off valves on the San Francisco Peninsula, and we plan to automate a total of 228 valves in our service area through 2014. These automated valves will be primarily located near earthquake faults and in densely populated areas.
* We have taken an aggressive and unprecedented effort to verify the accuracy of our records and to validate safe operating pressures for our system by conducting detailed engineering analysis of millions of documents and conducting numerous validation digs to visually confirm pipeline characteristics.
* We are hiring more than 90 new gas engineers as well as additional project managers, mappers and other employees in a major nationwide recruiting effort.
Beyond that, we’re continuing to look across the country to identify and adopt industry best practices utilized by the other gas utilities.
We’re also looking at the latest technologies available to help us do our job more effectively and efficiently. For example, we are conducting a first-of-its-kind study to determine the effectiveness of different aerial gas leak detection technologies. If proven reliable, this new technology will be incorporated into PG&E’s leak detection program to complement our ground patrols.
While we are taking these aggressive actions to improve the safety of our gas operations, we’ve reduced pressure on a number of our lines to provide an additional margin of safety. We will only return operating pressure to normal levels on these lines once we have thoroughly demonstrated it is safe to do so.
We are taking all of these aggressive actions to improve the safety and strength of our gas system for our customers. We understand that customers have questions and concerns about the pipelines in their area, and we are here to help address those concerns and win back our customers’ trust.
Customers with questions about the gas pipelines in their area can call our gas transmission pipeline hotline at 888-743-7431 between 7 a.m. and 6 p.m. Monday through Friday or visit our website atwww.pge.com/gassystem for more information.
Q: Is a seam in a pipeline an inherent safety problem, or is it only a problem when the seam is done badly or very old?
A: Typically, double submerged arc welded (DSAW) seams are very reliable. PG&E is currently investigating why the DSAW seam on this segment of Line 300B failed during the pressure test.Tags: Atlantic Leak Detection, New Jersey, New York Leak Detection, PG&E fields questions about pipeline rupture
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