About 6:45 p.m. on June 9, 1994, a 2-inch-diameter steel gas service line that had been exposed during excavation separated at a compression coupling about 5 feet from the north wall of John T. Gross Towers, an eight-story retirement home operated by the Allentown Housing Authority at Allentown, Pennsylvania. The failed UGI Utilities, Inc., service line released natural gas at 55 psig pressure, and the escaping gas flowed underground to Gross Towers. The gas passed through openings in the building foundation, entered the mechanical room through floor vents, and migrated to other building floors.
An Environmental Preservation Associates, Inc., employee, who had been using a backhoe to excavate fuel-contaminated soil from the area, detected the odor of gas and heard a third-floor resident shout that she smelled a strong gas odor. The employee went to a building entrance and encountered a very strong odor of natural gas. He told his foreman, who, after having the backhoe shut down, telephoned the gas company and the housing authority, telling them of the gas odor. The foreman then instructed other employees to locate and shut off the gas line valve.
About 6:58 p.m., the natural gas that had accumulated within the building was ignited, causing an explosion. A second explosion occurred about 5 minutes later. At the time of the explosion, many of the Gross Towers and Towers East residents were out of the building. The accident resulted in 1 fatality, 66 injuries, and more than $5 million in property damage
We determined that the probable cause of
the natural gas explosion and fire at Gross Towers in Allentown, Pennsylvania, was the failure of the management of Environmental Preservation Associates, Inc., 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 Environmental Preservation Associates, Inc., to notify UGI Utilities, Inc., that the 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, which could have rapidly stopped the flow of gas once the service line was ruptured. Also contributing to the severity of the accident was the absence of a gas detector, which could have alerted the fire department and residents promptly when escaping gas entered the building.
As a result of this investigation, we made the following new safety recommendations.
To the 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. (P-96-2)
To the States and the District of Columbia.: Require gas distribution operators to install excess flow valves in all new or renewed gas service lines, when operating conditions are compatible with commercially available valves, including service lines supplying schools, churches, and other places of public assembly.(P-96-3)
To the UGI Utilities, Inc.:
- Require that people handling emergency calls determine whether escaping gas is likely to enter a structure, and if so, require that the information be quickly conveyed to “911.” (Class II, Priority Action) (P-96-4)
- Modify its excavation-damage prevention program to include the review and close monitoring of any proposed excavation near a gas service line, including any line with unanchored compression couplings, that is installed near a building and that, if damaged, might endanger public safety significantly. (P-96-5)
- Instruct members of local governments and contractor groups in its service area about the threat to public safety posed by a gas line that is unsupported or damaged, and emphasize the importance of reporting such information immediately to the facility owner. (P-96-6)
To Environmental Preservation Associates, Inc.: Instruct its employees on actions to take when buried facilities, such as gas lines, are unsupported or damaged; such actions should include alerting local response agencies and residents of threatened buildings, initiating evacuations, and notifying facility owners. (P-96-7)
To the Governor of the Commonwealth of Pennsylvania:
- Require any person or entity that excavates to participate in the State's excavationdamage prevention program.(P-96-8)
- Designate a single State agency responsible for the State's excavation-damage prevention program; give the agency the power to levy administrative penalties. (P-96-9)
- Require each contractor to outline the area of the proposed excavation before asking the facility operators to mark the locations of their facilities.(P-96-10)
- Instruct fire and other city inspectors to advise facility owners, such as gas companies, immediately about any suspected damage to their buried facilities or any lack of structural support. (P-96-11)
- Require as an excavation-permit condition that the excavator instruct his workmen in how to help members of the public in the immediate vicinity of an emergency, how to notify the local response agencies and the owner of a damaged facility, and how to evacuate anyone who might be in danger. (P-96-12)
: Urge its members to instruct their inspectors to report observed or suspected damage to a buried facility, including lack of support, to the owner immediately.(P-96-13)
To 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. (P-96-14)
