By Tom Coolidge and Tom DeWitte
On rare occasions natural gas from a leaking pipe accumulates inside a building. Gas-filled buildings are known as “Gas-Filled Occupancies” or GFOs for short. GFOs pose an obviously high level of risk due to the potential of an explosion if the accumulation ignites. The question needing answered by first responders and all in proximity to the building is just how far away from a GFO do they need to be to be safe? And the natural follow-on question is how can first responders best be aware of that answer during their emergency activity?
In terms of existing industry practice, there is no one industry-standard answer to those questions. Each gas utility determines its own policy and practice based on its own unique circumstances and environment. Callers reporting an odor of gas sometimes are told to move outside at least 330 feet away, while others are told to move some other given distance based upon the gas utility’s own criteria or to an unspecified “safe location.”
Gas utilities now can better answer those questions for themselves thanks to an initiative of the American Gas Association (AGA).
The AGA’s Gas-Filled Occupancy Task Force that was initiated by the AGA Safety and Occupational Health Committee evaluated a decade of GFO explosions to examine the risk relationship between the GFO explosion location and the location of resulting fatalities or injuries.
The criticality of GIS as a tool for first responders and all involved in GFO incidents jumped off the pages to me as I read the Task Force’s recent “Gas-Filled Occupancies – Emergency Response” technical paper. Reading the AGA paper also reminded me of one of my favorite IMGIS 2021 Conference presentations that focused on the use of GIS in GFO response situations.
The research done by the Task Force found that there were 78 fatalities and approximately 350 reported injuries as a result of a GFO explosion between 2010 and 2020. Not surprisingly, in general, the further a person is away from a GFO explosion, the safer they are. It was concluded that utility worker and fire department fatalities typically occurred within 50 to 100 ft of structure. Most injuries related to a GFO explosion typically were within 100 to 200 ft of the structure and could be characterized as typically minor.
If you haven’t already, I strongly encourage you to read the Task Force technical paper. It is really good work on a topic of obvious importance!
The AGA Task Force work is specific to GFOs. Among previous guidance referenced by gas utilities is another that is more general. That reference is found in the U. S. Department of Transportation Emergency Response Guidebook. The guidebook specifies there should be a 100-meter (330 feet) evacuation distance from a natural gas leak in an open area.
Given the Task Force’s findings, one approach we expect to see more of is the designation of different zones based on specified distances from a building. The zone closest to the GFO being the highest risk zone, the one furthest away the lowest. This is where a modern GIS can play a significant role. GIS can present all responders and those supporting them with a common operating picture indicating both levels of risk within a certain distance of a building and the location of pipe network components that can isolate the area to make the building – and them - safe.
An early example of this approach was highlighted at Esri’s 2021 IMGIS Conference in a presentation titled “How close is too Close?” by Lindsay Dreckman of the Metropolitan Utilities District of Omaha, Nebraska (M.U.D.).
Based on the work done by the Task Force, M.U.D. knew the distances from GFO incidents where most fatalities and injuries occurred. M.U.D.’s goal number one was to create a tool to generate three safety zones. Looking at the M.U.D. GFO emergency response policy, those zones include Exclusion, Hazardous, and Risk-Reduction. The Exclusion Zone is from the building’s exterior wall to 100 ft and where zero of our personnel are permitted to access. From 100-200ft is the Hazardous Zone, where work can occur but only after coordination with the public safety incident command. And from 200-330ft is the Risk-Reduction Zone, where we can establish a command post but with protection from a potential explosion.
It is important to remember that this is an emergency event. Field crews and first responders need both an immediate visual aid and an automated warning to inform them of these safety zones.
A mobile application with an interactive map, such as ArcGIS Field Maps is ideal for this need. Here is an example highlighting that capability. When this mobile application is loaded onto the field technicians’ phone, or tablet, they will have a mobile device that informs them of these risks. This is possible because today’s mobile devices are location aware. The map can display their location with imagery of the area and the safety zones overlayed.
Recent enhancements to ArcGIS Field Maps now enable client side notifications based on that mobile device location awareness. This is called geofencing. With geofencing the same field technician can have their mobile device vibrate, make sounds and have a banner notification appear on the mobile device when they approach the safety zones. This client side notification is unique because it works regardless of the phone connection to the network.
All in all, it turns out that the AGA Task Force now gives gas utilities an extremely valuable reference to inform their decision-making on GFO response policies and practices. And, not surprisingly, location is key. That puts GIS at the heart of improving safety in a fast-evolving and understandably hectic time of emergency response.
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