Pacific Gas and Electric Company (PG&E) will perform a series of hydrostatic pressure tests on a number of gas transmission pipeline segments throughout its system beginning in May in Antioch and Mountain View.

As described in PG&E’s March 15 filing with the California Public Utilities Commission, the work is part of the company’s effort to pressure-test or replace approximately 150 miles of pipeline segments in high consequence areas that have characteristics similar to the pipeline involved in the tragic accident in San Bruno on Sept. 9, 2010.

“Our number-one responsibility is the safety and reliability of our natural gas transmission pipeline system for our customers,” said Kirk Johnson, vice president of gas engineering and operations for PG&E. “These tests will be conducted using safe and proven methods that are used throughout the nation. These tests will validate that the pipelines are operating safely.”

PG&E will hold open houses in both Antioch and Mountain View prior to the tests to answer questions about the testing. Customers in these areas will begin receiving letters this week regarding the open houses and information on the testing.

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 eight hours. Any pipe sections that do not meet acceptable standards during the test will be replaced with new pipe that has already passed a pressure test. Following a successful test, the section of pipe is emptied of water, dried thoroughly and placed back in service. PG&E will provide updates on progress as hydrostatic testing work proceeds. This process will validate the safe operating pressure of the pipeline.

Hydrostatic pressure tests take about two weeks to complete and require pipeline segments to be taken out of service for several days. PG&E will continue to provide gas to customers from an alternate source while work is in progress. Service will not be interrupted.

Because PG&E safely empties the gas from the pipeline segments prior to hydrostatic testing, customers may smell gas in the area of the tests. Residents concerned about the smell of gas are encouraged to call the company’s 24-hour customer service line at 800-743-5000 or call 911 immediately.

Customers may also see temporary traffic safety cones and detour signs, PG&E and PG&E-contracted field personnel, testing equipment (such as above-ground pipes and valves), and machinery and support equipment (such as excavators and water tanks).

PG&E also plans to conduct several pipeline assessment tests throughout the Bay Area. This work may require crews to excavate around the pipe, X-ray welds, test the strength of the pipe or use a robotic camera to inspect the inside of the pipe.