Pacific Gas and Electric Corporation (PG&E) operates a major natural gas transmission and distribution system consisting of 40,123 miles of natural gas distribution pipelines and 6,136 miles of transportation pipelines that provides natural gas to 4.2 million natural gas customer accounts. By nature of the geography and seismic activity that PG&E’s system traverses, the ability to quickly assess and respond to emergencies that affect the pipeline infrastructure—such as earthquakes, landslides, etc.—is a critical focus of PG&E’s operations.
Remote sensing techniques using aircraft to detect methane leaks such as the DIAL Lidar technology developed by ITT’s Airborne Natural Gas Emission Lidar (ANGEL) Services has emerged as a fast and efficient means of surveying for leaks in natural gas transmission pipelines during normal operations. During a recent evaluation of the ANGEL Services system, PG&E realized there is an additional opportunity to leverage ANGEL Services’ speed and performance to quickly survey areas affected by natural disasters. In November 2008, PG&E and ITT teamed up to design, test, and validate a conceptual strategy for rapid emergency response using ANGEL Services’ technology.
ITT received financial support from the United States Department of Transportation (USDOT) to enhance the capabilities of ANGEL Services to provide rapid response information on leaks in natural gas or other hazardous-materials pipelines in times of natural or manmade disasters. The primary goal of the USDOT funding was to develop a rapid response and quick reporting capability for emergency situations following disasters such as earthquakes, hurricanes, floods, landslides, or explosions. The funding came through an extension of a contract with USDOT PHMSA (Pipeline and Hazardous Material Safety Administration) under which ITT’s airborne leak detection sensor technology used in ANGEL Services was successfully enhanced to remotely detect and quantify small leaks of hazardous liquids, such as gasoline, diesel fuels, and propane.
Natural gas pipeline surveillance
As a provider of airborne natural gas leak detection services, ANGEL Services flies a methane-tuned differential absorption lidar (DIAL) sensor in a Cessna Grand Caravan (Figure 1). For those not fully familiar with DIAL, ANGEL Services operates a multiple-laser system that detects methane absorption—and thus the presence or absence of elevated natural gas levels over the survey route. Firing 3,000 laser pulses per second at the ground, the detection of methane is accomplished by measuring the strength of laser energy returned at a wavelength unique to methane and comparing it to the return at a wavelength which methane does not absorb. The ANGEL Services aircraft flies over pipeline corridors at 120 mph, instrument-surveying long, straight pipelines significantly faster than any other method. The sensor suite also collects high-resolution orthorectified imagery and video as part of the service offering, providing value-adding tools to help quickly pinpoint leak sources on the ground. These imagery tools also provide sharp visual context to help identify encroachments and/or other potential threats to pipeline integrity.
Traditionally, pipeline surveillance is performed qualitatively (i.e., visually) by aerial patrol, driving patrol, and/or walking inspection to record features along the right-of-way that are important to and/or may impact the pipeline’s safety and security. However, these manual survey techniques produce results that can miss leak indications (Figure 2) that are often precursors to more significant problems, as was validated during this evaluation survey. Furthermore, the results of current manual survey methods are difficult to compile quickly, and impossible to monitor on a large scale, especially under emergency conditions.
By contrast, the use of ANGEL Services and the deployment of targeted quantitative applications and tools can enhance
the quality of information available while simultaneously reducing costs. Increased data densities, reliable analyses, and greater coverage of corridors give pipeline operators a more cost-effective, accurate, and rapid means to evaluate the safety, security, and reliability of pipeline corridors.
Looking forward, the natural gas pipeline industry would benefit from a rapid and efficient means for assessing the safety and security of pipelines in emergencies. Inevitable disasters, whether natural or manmade, often cause extensive loss of human life and massive property damage, and create major impacts on regional and national economies. Although utilities and pipeline companies usually have engineering data detailing the construction and location of their facilities, they generally lack a rapid-response emergency-information-gathering capability that is truly responsive to large-scale pipeline emergencies in real time. With major safety concerns and increasing threats such as terrorism, a compelling need exists to quickly assess the geographic extent of major pipeline disasters, their proximity to population centers, their juxtaposition to other structures, and the consequences of their disruption.
Assessing pipeline integrity
Following disasters, natural gas pipeline operators need to rapidly and efficiently assess the integrity of their high-pressure transmission pipelines and related facilities to quickly identify and address leaks and areas of danger. After a major earthquake, for example, the destruction of roads, bridges, lines of communication, and/or electrical power facilities may well preclude using traditional methods of pipeline inspection and leak survey (i.e., walking or driving).
Obtaining useful situational awareness data for a central command center is a major challenge during an emergency. In addition, first responders typically encounter significant safety risks: many changes in the right-of-way are often difficult or impossible to assess visually due to a lack of sufficient information on the pre-disaster condition
of the pipeline corridors.
A natural or manmade disaster could also generate a psychological response to the loss that multiplies the impact beyond the actual damage itself. Thus, even when the actual damage may turn out to be minimal, there is an urgent public need for accurate information to quell public fears and concerns.
A key challenge in ground-based emergency response is the need for specialized manpower that is typically required to survey the affected infrastructure in real time. Prioritizing assessment and repair activities may also lead to delayed surveying of outlying and/or more-remote pipeline assets. Similarly, specialized staff with direct knowledge of the affected assets may be deployed elsewhere, further delaying time-critical response. The rapid collection and distribution of leak detections and high-resolution images via the internet would support a distributed-analysis model of emergency incidents making efficient use of scarce, critical manpower.
Rapid emergency response
During a recent evaluation of ANGEL Services on PG&E gas transmission line segments, the observed speed of the pipeline surveys suggested that this technology can be a particularly effective tool for conducting pipeline infrastructure surveys in emergency situations. Flying at 120 mph approximately 1,000 feet above the destruction, ANGEL Services is not hampered by rubble, road closures, or other ground obstructions that often make a ground survey problematic, slow, and dangerous.
The PG&E / ANGEL Services’ evaluation showed that the most recent generation of ITT’s airborne DIAL has the appropriate speed, maneuverability, and resolution requirements needed for the routine collection of data in monitoring natural gas transmission pipeline rights-of-way. The testing done with PG&E also confirmed that the ANGEL Services’ sensor has the sensitivity needed to perform the necessary tasks. In the November 2008 evaluation of PG&E pipelines, ANGEL Services found 100% of the staged leaks of 250 scf/h or greater — as well as some smaller leaks — all without any false positives. This translates into a capability of finding a leak smaller than a pinhole in a high-pressure underground gas transmission pipeline.
As an emergency-response pipeline integrity solution going forward, the implementation of ANGEL Services’ surveys will likely improve coverage, collection reliability, and flexibility while reducing the need for current aircraft and ground-based data collection systems.
Earthquake response procedure
PG&E currently uses a Geographic Information System (GIS)-based procedure to enhance their emergency response following significant earthquakes. The Gas Transmission Earthquake Plan and Response Procedure (GTERP) is a key part of PG&E’s Pipeline Integrity Management Program.
Computer models, which access Internet-data resources and digital geohazard maps for California, are used with decision-support tools to prioritize emergency response activities.
Used as a screening tool, GTERP provides early information to rapidly identify potential gas transmission problem areas prior to receipt of initial damage reports from the field. The response efforts are focused on appropriate areas through the use of real-time ShakeMaps derived from empirical observations and earthquake information (location and magnitude) and calculated Earthquake Risk Values (ERV). These ERV are determined by combining information from potential or actual earthquakes with digital information from geologic maps that identify liquefaction and slope failure hazards associated with large earthquakes.
Preparation for an emergency
Not surprisingly, preparation is a critical aspect of any emergency response. For example, GIS locations of existing pipeline (particularly older pipes which may be more prone to damage) are not always accurate. It is therefore very important to find and correct these spatial database errors before an emergency occurs to insure that the sensor will pass over the pipe.
PG&E and ITT collaborated in an effort to develop a conceptual approach for using ANGEL Services’ technology for emergency response. The resulting approach requires modifications to current practices and anticipates future technology improvements. Figure 3 identifies the existing and future elements of preparation, mission planning and execution, and data analysis and delivery that could provide an emergency response capability for a gas transmission line emergency. Optimal preparation for emergencies starts with collaboration between ANGEL Services and the pipeline company, before an actual emergency.
Further information on ITT’s ANGEL Services can be found on the web at http://www.ssd.itt.com/angel.
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