As part of its overall natural gas pipeline integrity program, San Diego Gas & Electric (SDG&E) today is announcing a number of pipeline-related safety tips and activities. The utility would like to remind customers to call 811 before they dig, to report any construction or damage around natural gas pipelines, and to call the utility immediately if odors of natural gas are detected within or outside the home or business.
This intersection of a natural gas pipeline and a sewer line, called a crossbore, is rare and typically not a risk if left undisturbed. A crossbore, however, can result in a safety risk when a homeowner or plumber attempts repair work to a sewer line using mechanical cleaning or snake machines. These machines could sever a gas line and cause a gas leak, which could result in a dangerous situation. Although SDG&E has found only one plastic natural gas pipeline crossbore in its history, the utility is taking the extra proactive steps to ensure customer safety and draw attention to the situation.
To address possible crossbores, the utility is starting a proactive, five-year safety inspection program in areas most likely to experience this phenomenon. SDG&E estimates that the areas potentially affected involve only about 6 percent of the company's 850,000 natural gas customers. The inspection program will occur in portions of the greater San Diego area and will involve lowering a thin cable and camera into the sewer line. The company will be sending letters to affected customers in advance of any inspections.
Customers who are concerned that their clogged sewer line may intersect with a natural gas pipeline can call SDG&E at (800) 411-SDGE (7343). The company will have trained staff ready to respond 24/7 to assess the area for crossbores and determine precautions and next steps.
Crossbores are an emerging issue for the nation's gas utilities and SDG&E is one of several utilities in the nation to initiate an aggressive inspection program. The methods leading to crossbores, horizontal directional drilling and pneumatic boring, first occurred in the 1970s and avoided opening large trenches to install pipelines and instead bore horizontally underground, minimizing damage to yards and streets. However, in the process, a plastic or metal natural gas pipeline might have bored through some sewer pipelines made of clay or other porous materials.
Improvements in technology and construction practices have reduced the possibility of crossbores. Additionally, in 2008, SDG&E began installing safety devices that restrict gas flow in the event a service line is severed. The company also has advanced video equipment available to inspect sewer lines before and after installing another utility pipeline.
Any time customers smell natural gas they should evacuate the premises, not turn on lights or other appliances that could cause a spark, including lighting matches, candles or cigarettes, and call (800) 411-SDGE (7343).
"We take natural gas pipeline safety very seriously and, although we do not expect to find very many instances of natural gas pipelines within sewer lines nor do we anticipate any associated natural gas leaks or damaged pipes, we ask our customers always to exercise safety around underground utilities and to call us anytime they smell natural gas odor or have any questions or concerns," said Bret Lane, vice president of field services for SDG&E.
SDG&E also is reminding customers to call Underground Service Alert by simply dialing 8-1-1 at least two business days before digging in their yard. As a free service, Underground Service Alert will contact SDG&E and other area utilities. Each utility then will locate and mark the underground facilities they own.
SDG&E-owned pipelines typically extend from the gas main, in front of or behind the home, to the gas meter.
Customer-owned piping is the line that runs beyond the gas meter to a building or area where gas-fueled equipment or appliances are located. To have these customer-owned lines located and marked, SDG&E advises customers to call pipe and leak locating service companies or plumbing contractors who provide these maintenance services.
"Once all lines are marked, customers should carefully use only hand-digging tools within two feet on each side of marked gas lines," Lane added.
No pipeline damage is too small to report. Even a slight gouge, scrape or dent to a pipeline or its coating could cause a dangerous break or leak in the future. If a customer causes what seems to be only minor damage to a pipeline, or any component attached to the pipeline, he or she should still notify SDG&E immediately.
In addition to these customer-oriented activities, the company's pipeline integrity program involves annual patrols of its 250 miles of major natural gas transmission pipelines, the 24/7 monitoring of these large transmission pipelines' pressures and visual inspections for factors that could indicate pipeline damage.
SDG&E also has begun retrofitting segments of a 51-mile transmission pipeline that stretches from Rainbow to San Diego’s Miramar area. This retrofit will include installing pipe supports, fittings and valves that will enable a sophisticated sensor to traverse the pipeline's interior. From mid-2011 to March 2012, a total of 19 retrofit excavations will be made at locations in Rainbow, Fallbrook, Vista, Encinitas, Carlsbad and San Diego.
SDG&E is a regulated public utility that provides safe and reliable energy service to 3.5 million consumers through 1.4 million electric meters and more than 850,000 natural gas meters in San Diego and southern Orange counties. The utility's area spans 4,100 square miles. SDG&E is committed to creating ways to help our customers save energy and money every day. SDG&E is a subsidiary of Sempra Energy (NYSE: SRE), a Fortune 500 energy services holding company based in San Diego