Priorities In Dealing With Gas Line Hits

By Jeff Griffin, Senior Editor | April 2013, Vol. 68 No. 4
Jerry Gann

• Do not backfill an excavation where the pipe was hit;
• Do not fill in a bore hole in which the pipe was struck;
• Do not attempt to put out a fire if escaping gas ignites; and
• Do not attempt to repair the damaged pipe.

Gas properties

In regards to the first ‘don’t,’ Gann said leaking gas will take the path of least resistance which can be a water or sewer pipe, the space between a tree root and surrounding soil or other available conduits. However, an open excavation allows the gas to escape into the outside air where it will rise and vent into the atmosphere, helping to dissipate from the site of a leak.

A basic understanding of the characteristics of gas can help workers better understand how to deal with a gas line accident.

Gas is a naturally occurring hydrocarbon composed of methane (CH4), which is principally found in underground formations of porous rock. It is colorless, odorless, tasteless, flammable, non-toxic and lighter than air. In its natural state, it is not possible to see or smell it. For safety reasons, Mercaptan, a chemical odorant that smells a little like rotten eggs, is added to natural gas so that it can be smelled if there is a gas leak.

Natural gas has a limited range of flammability of 5 to 15 percent gas-to-air mixture. The ignition point of gas is high -- 1,000 to 1,200 degrees Fahrenheit.

Gann said that by understanding the characteristics of natural gas, construction personnel can make informed decisions about how to react when a gas pipeline is damaged.

“Making sure the public is safely evacuated, securing the area and calling 911 and the gas company are key front lines of defense to ensuring the situation does not get worse,” he said. “Once the emergency responders and gas company personnel are on the site, the excavator should set up liaison activities with those groups to disseminate key information and offer any needed assistance. Gas company personnel will make the necessary repairs to shut off the flow of natural gas.”

The best way to avoid all the problems resulting from accidental utility hits is to prevent them such as simply calling 811 before digging.

Accurately locating and marking underground facilities is the first step in preventing damage to buried infrastructure, and the nation’s 811 One-Call System provides a means for locating and marking underground facilities before construction begins. On private property projects or where utilities are operated by organizations who are not members of One-Call, other methods are necessary to identify and mark the locations of underground lines.