On June 22, 2004, at approxi-mately 1730 hours, the Setauket (NY) Fire Department responded to a natural gas emergency in an incorporated village in the northernmost part of our fire district in Long Island.
As with most volunteer fire departments you get who you get when the alarm is activated.
For this alarm, two Class A pumpers, an assistant chief, a first responder paramedic, and a fire police van responded with approximately 16 personnel. While we were mustering out, our dispatcher notified the county police dispatcher and the gas company. The county police department sent two sector cars and the village’s constable. The gas company sent one worker in a van.
On arrival, the sector cars and the constable parked along the western road edge within 100 feet of the site. They confirmed that the source of the leak was a ruptured natural gas line. The constable then relocated his vehicle about 200 feet north of the site and started traffic control.
Since it was June, the sun would not set for another 31⁄2 hours, and the ambient temperature was 68°F. The winds were out of the northeast at five mph, gusting to 13 mph, and the relative humidity was 50 percent.1 At the incident location, a crawler excavator and a 10-wheel dump truck were parked adjacent to an open, unprotected excavation in the middle of the driveway leading to the dwelling under construction. The site was approximately 100 feet west of a narrow north-south two-lane secondary road. Exposures consisted of an occupied private dwelling with children playing in the yard, 150 feet due south of the incident location; the unoccupied dwelling under construction immediately more than 100 feet due west of the incident location; and another private dwelling 250 feet due north of the site.
On arrival, the fire chief and first responder each parked off the secondary road in an adjacent driveway. A recently installed hydrant, located on the same side of the road as the excavation, was within 100 feet of the scene; the next nearest hydrant was within 1,000 feet of the first.2 Soon after, both pumpers arrived and parked one behind the other, the second pumper connecting into the nearby hydrant.
(1)An excavator similar to this one was involved in this incident. (Photos by author.)
At this point, all of the emergency vehicles with the exception of the fire police van and constable’s car were parked less than 100 feet east of the excavation along the shoulder of the north-south secondary road.
PROBABLE CAUSE AND DELAYS
The contractor had been using the crawler excavator to expose a water main (photo 1). While removing soil, the operator struck the water main, causing it to crack; the resulting flooding undermined the gas yard line.3 The gas company emergency repair crew determined later that the lack of support for the gas pipe permitted it to flex and created a two-inch crack, releasing pressurized natural gas. The excavator was quickly abandoned in place-many of the workers withdrew behind a dump truck, another worker moved it an additional 75 feet farther west of the excavation. At this location, someone made a cell phone call for help.
On arrival, the gas company representative was apprised of the gravity of the situation. He then reclassified the leak and had an emergency repair crew respond. During his time on-scene he was unable to locate the valve box. The failed pipe continued to spew natural gas. Unfortunately, the fire department dispatch records did not indicate what type of leak had occurred, nor did it use the gas company’s classification system.
GAS COMPANY PROCEDURES
Regarding gas leak reports, the gas utility queries all callers for the same information: incident location, nearest cross street, and what is happening at the location. The company then classifies the leak as a Class 1 or Class 2. A Class 1 leak is considered a major leak and requires that the gas company respond with an emergency repair crew within 60 minutes. A Class 2 leak may be a generalized odor in the area. Often, when the site is located in a manhole or a vault, it is vented out by the utility and then followed up on within five or six months. If the odor persists, then the utility will send a regular repair crew. During Class 1 leaks, the utility provides emergency instructions to each caller covering evacuation and ventilation.
NATURAL GAS PROPERTIES AND DISTRIBUTION
Natural gas, depending on the Material Safety Data Sheet4 referenced, contains isobutene, methane, n-hexane, and other chemicals. Because the gas has a specific gravity of 0.06, it is lighter than air and rises. It has a flash point of 292°F, a lower explosive limit (LEL) of 4 percent, and an upper explosive limit (UEL) of 15 percent and produces 1,400°F of radiant heat. The last figure is relative. Although the gas is considered nontoxic, it is an asphyxiant and, in the presence of n-hexane, can cause lung and nerve damage.
It is delivered through a distribution system composed of street mains and yard lines. The pressure in these lines is between 60 and 125 psi. A typical distribution system with 600 feet of two-inch-diameter pipe flows 390 cubic feet per hour (cf/h), three-inch-diameter pipe flows 1,030 cf/h, and four-inch diameter pipe flows 2130 cf/h.5
By multiplying the cf/h by 1,000, you can determine the amount of British thermal units (Btus) the gas flow will produce when the LEL of 4 percent is reached: two-inch pipe, 390,000 Btus; three-inch pipe, 1.3 million Btus; and four-inch pipe, 2.1 million Btus.
The sector cars, the chief’s and the paramedic’s vehicles, as well as both Class A pumpers may well have been too close to the scene. Although the gas did not appear to be migrating through the soil (Class C),6 the intermittent winds out of the north-northeast caused the gas plume to blow toward the south side dwelling and emergency vehicles, which presented potential ignition sources.
More importantly, operating personnel were placed at risk. SCBAs were not used, and some personnel had taken off their PPE because of the warm weather. The U.S. Department of Transportation North American Emergency Response Guidebook indicates that natural gas is extremely flammable and easily ignitable and that vapors may travel to an ignition source and flash back. It indicates that as an immediate precautionary measure, responders should isolate the leak area for 100 meters (330 feet) in all directions, keep unauthorized personnel away, and stay upwind.7
The construction workers, the children, and the occupants of each adjacent residence were never removed to a safe location. A safe location would have been anywhere upwind more than 100 meters (330 feet) from the excavation. The first-arriving pumper crew should have accomplished this immediately on arrival. As a result, all personnel and civilians (including children) were exposed to an IDLH (immediately dangerous to life and health) condition!
(2) Damaged three-inch natural gas yard line.
Had the free-flowing pressurized gas plume ignited, all of our personnel, the civilian contractor’s employees, children, and the police officers within 100 to 200 feet of the excavation would have been in jeopardy. The police cars and engines would have most certainly been damaged. Department members not injured during initial self-rescue would be exposed to extreme levels (1,400°F) of radiant heat.
Fortunately, the gas did not ignite, and the gas company eventually restored service. However, if it all went south in a hurry, there would be a lot of unpleasant issues to deal with.
Another concern: The contractor had employees in an excavation that was deeper than five feet but without benching or any trench protection whatsoever. Occupational Safety and Health Administration (OSHA) regulation 29 CFR 1926 is the law for trench protection and confined space entry in construction. If we had been required to go in there and pull them out, it would have really complicated the evening, as this would have been a confined space rescue, in which only certified and trained personnel can enter the space.
Emergency dispatch. Emergency dispatchers should use the gas utility’s query system/checklist for all calls reporting a gas emergency and be familiar with the utility’s terminology and procedures. They should reference the current U.S. DOT Emergency Response Guidebook and relay all necessary information to the incident commander.
Maintain a safe distance on arrival. Chief officers or officers in charge must stop several hundred feet from the scene, upwind if possible, and wear full personal protective equipment (PPE)/SCBA. The incident commander should always walk, not drive, to the incident location and use a combustible gas detector to check from the lowest (farthest away) to the highest (closest to the site) concentration for the potential of an LEL.
PPE/SCBA. All firefighters must wear full PPE and SCBA until the emergency has been terminated. SCBA usage may be discontinued once personnel are withdrawn to a safe upwind location. All fire department personnel operating (rescue, metering, and protection) inside an IDLH incident location must be on SCBA air.
Safety officer. Always assign a safety officer and call for a RIT/FAST truck.
Accountability. Rescue everyone in the IDLH area: account for contractor employees and civilian adults and children. Take everyone to a safe location upwind of the site. Remove occupants from adjacent structures and take them to the safe location. A safe location is determined by several factors including the amount of leaking gas, gas pressure, the wind and weather conditions, and the possibility of underground migration of gas.
Reverse lays. In this incident, both Class A pumpers should have dropped off portable deluge guns and then reverse laid to two independent hydrants where they could have supplied master streams and significantly reduced exposure of their members to gas vapor or a flash fire potential.
Firefighters in full PPE/SCBA should accompany gas utility personnel at the incident. Assign several firefighters in full PPE/SCBA with appropriate-sized and charged hoselines to accompany gas utility personnel in the incident location. During large-scale operations, request that a gas utility representative work directly with the incident commander.
Keep unprotected police officers out of an IDLH area. The police can’t go anywhere they want just because they’re the police. You are still responsible.
Traffic control. Check local laws regarding traffic control at the incident, New York State law permits a fire policeman (a peace officer by statute) to control traffic during a fire emergency. A fire chief has complete control of the scene under laws dating back to the 1800s; although he may close roads and evacuate residences, he is ultimately held accountable. One Long Island fire chief was held accountable to the Federal Communications Commission for cursing on the air in the 1960s at a gasoline tank truck rollover and fire. ■
1. National Oceanic and Atmospheric Agency/National Weather Service Web site: www.nws.noaa.gov.
2. Telephone interview with District Secretary, December 15, 2004.
3. Keyspan Energy Customer Service records, June 22, 2004.
4. Phillips Petroleum Company, Bartlesville, Oklahoma, General MSDS Information: (918) 661-8327.
5. Gas Carrying Capacity of House Piping Chart, Engineering Toolbox Web site: http://www.engineeringtoolbox.com/gas-pipes-capacity-22_480.html .
6. OSHA regulation 29 CFR 1926.650, Appendix A to Subpart P, Soil Classification.
7. 2004 Emergency Response Guidebook, Guide # 115, U.S. Department of Transportation.
■ GREGORY P. PERRICONE is a safety specialist with a Property and Casualty Insurance Company in New York City. Currently a member of the Setauket (NY) Fire Department in Long Island, he has more than 32 years of fire service experience, having served in the United States Air Force, with the Tampa (FL) Fire Department, and as fire marshal at the State University of New York at Stony Brook. He has a bachelor’s degree in fire and safety administration from SUNY Empire State College and is a New York State certified fire instructor II and haz-mat technician.