Citing the critical need to move now, the National Transportation Safety Board called on the Governors of all States that have gas distribution systems and the Mayor of the District of Columbia to require installation of excess flow valves (EFVs) on new and renewed gas distribution service lines, including service lines supplying schools, churches, and other places of public assembly. The Safety Board said that its recommendations on EFVs date back to 1971 and that the issue has been on the Board's "Most Wanted List" of recommendations since its inception.
The Board's recommendations were contained in its final report on the natural gas explosion that occurred June 9, 1994 at the Gross Towers Apartment retirement complex in Allentown, Pa. The explosion killed one person, injured 66 persons and caused more than $5 million in property damage. The Safety Board stated that had an excess flow valve been installed at the eight-story apartment building the consequences of the accident could have been substantially reduced and the likely result would have been no injuries or deaths.
The Safety Board noted that had the Department of Transportation (DOT) adopted our 1971 excess flow valve recommendations, as many as 30 million homes would be protected today, instead of just over one million. The Board concluded that over the past 20 years the DOT's Research and Special Programs Administration has failed to effectively assess the benefits of excess flow valves and has failed to promote their use.
Excess flow valves are inexpensive safety devices that are usually installed in the gas line at the point where the customer service line joins to the gas main line in the street. If there is an excessively large flow of gas in the service line, as happens when there is a rupture, the EFV will stop the flow of gas into the service line until the problem has been determined, thus limiting the amount of gas that might leak into a home or larger building. Gas operators reportedly respond to more than 30,000 instances of excavation-caused gas line ruptures annually; those that EFVs were specifically designed to control. A single Ohio-based gas operator with 8,000 EFVs installed reported that during a recent 18 month interval 144 of the valves activated due to excavation-caused damage minimizing the potential of catastrophe.
In the Allentown accident, the gas explosion occurred at about 6:45 p.m. on June 9, 1994, when a 2-inch-diameter steel gas service line that had been exposed during an excavation separated at a compression coupling about 5 feet from the north wall of the eight-story building. The escaping gas flowed underground into the building foundation, entered the mechanical room through floor vents, and migrated up to other building floors.
The Safety Board determined that the natural gas explosion and fire was the failure of the management of Environmental Preservation Associates, Inc.(EPAI), to ensure compliance with OSHA's and its own excavation requirements through project oversight.
Contributing to the accident was the failure of the workmen from EPAI to notify UGI that the gas line had been damaged and was unsupported. Contributing to the severity of the accident was the absence of an excess flow valve or a similar device, that could have rapidly stopped the flow of gas once the service line was ruptured. Also contributing was the absence of a gas detector, which could have alerted the fire department and residents promptly when gas entered the building.
In addition to it's recommendation to States and jurisdictions with natural gas distribution systems to require excess flow valves, the Safety Board also recommended that:
--the Department of Transportation's Research and Special Programs Administration:
- Require gas-distribution operators to notify all customers of the availability of excess flow valves; any customer to be served by a new or renewed service line with operating parameters that are compatible with any commercially available excess flow valve should be notified; an operator should not refuse to notify a customer because of the customer's classification or the diameter or operating pressure of the service line.
--the Department of Housing and Urban Development:
- Require the installation of excess flow valves in new and renewed gas services to buildings that the Department has approved for Federal rent subsidies.
The Safety Board also made recommendations on other related issues to the Department of Housing and Urban Development, the Governor of Pennsylvania, the Associated General Contractors Association, the National Utility Contractors Association, and UGI Utilities, Inc.
The Safety Board's complete printed report, PB 96-916501, may be purchased from the National Technical Information Service, 5285 Port Royal Road, Springfield, VA 22161. The number is (703) 487-4650.