5. Discussion
Pursuant to Public Utilities Code Section 451 each public utility in California must:
Furnish and maintain such adequate, efficient, just and reasonable service, instrumentalities, equipment and facilities,...as are necessary to promote the safety, health, comfort, and convenience of its patrons, employees, and the public.
The duty to furnish and maintain safe equipment and facilities falls squarely on California public utilities, including PG&E. The burden of proving that particular facilities are safe also rests with PG&E.
The Executive Director and this Commission have taken extraordinary steps to restrict the operating pressure on certain of PG&E's natural gas transmission pipelines in response to the worst tragedy in California history from public utility operations. In D.11-09-006, the Commission set forth the specific requirements for PG&E to demonstrate that the operating pressure restrictions can safely be removed. These requirements begin with a pressure test complying with regulations applicable when conducted, and also require a responsible engineer's review of the pipeline construction and assessment of the pressure test results to ensure safe operations. The end result is that PG&E must be fully accountable for the pressure test and the assertion that the line can be safety operated at the restored MAOP.
5.1. Pressure Test Results
PG&E has presented complete pressure test results for the 11 segments pressure tested for the suction side of the Topock Compressor Station that had not been previously tested. The test results included hydrostatic test packages for each segment, as well as supporting documentation including test procedure, post hydro test leak survey results, ultrasonic thickness records, and carbon equivalency tests.
CPSD has examined these test results and found that the results substantially, albeit not perfectly, comply with applicable requirements and provide adequate assurance of fitness to operate at the restored MAOP of 660 psig.
PG&E has presented adequate pressure test results supporting its assertion that the suction side of the Topock can safely be operated with an MAOP of 660 psig. These test data show that pipeline facilities were subject to sustained pressure levels well above the minimum levels required to establish a MAOP of 660 psig, for a period of eight hours, with no failure of these facilities. The maximum pressure level of more than 50% above MAOP of 660 psig also well exceeds the 20% pressure reversal level at which the probability of pipeline failure, due to pressure reversal, is considered to be one in ten million.3 Thus, the ratio of the high test pressure to the intended MAOP of 660 psig effectively demonstrates the low risk of failure of these pipeline facilities.
Although CPSD found the testing adequate in this instance, CPSD identified several pressure testing deficiencies. We order PG&E to remedy all deficiencies noted in CPSD's September 12, 2011, memorandum for its future MAOP restoration requests.
5.2. Responsible Engineer's Review
PG&E's Vice President of Gas Operations, Standards and Policies, a Professional Mechanical Engineer registered with the State of California, testified under oath that PG&E's engineers have validated the engineering and construction, and performed hydrostatic pressure testing on all segments and components for which a prior pressure test result was not available. PG&E's Vice President concluded that in her professional judgment, the suction side of the Topock was safe to operate at the MAOP of 660 psig.
We, therefore, find that PG&E's responsible engineer has reviewed the engineering and construction of the segments, as well as the results of the pressure tests, and concluded that the MAOP may be safely returned to 660 psig.
5.3. PG&E is Accountable for Safe Operations at Restored MAOP
PG&E operates a natural gas transmission and distribution system. As the operator, PG&E must ensure that the system is operated safely. PG&E presented pressure test results, supporting information, and the testimony of its responsible engineer verifying that the Commission could safely rescind its operating pressure limitation and that PG&E could resume operations with a MAOP of 660 psig for the suction side of the Topock Compressor Station.
5.4. Conclusion
Therefore, we conclude that PG&E has demonstrated that the suction side of the Topock may be safely returned to its previous MAOP of 660 psig. We note further that consistent with 49 CFR 192 Subpart K, PG&E's pressure test results could be used as part of an operator's review required by 49 CFR 192.555 to justify a higher MAOP when conditions later permit.
3 See Memorandum from Michelle Cooke, Interim Director, CPSD, to PG&E, September 12, 2011.
