​At 6:19am on April 22, 1973, a violent explosion destroyed 7 of 15 units in an apartment complex in El Paso, Texas. Sever persons were killed and eight persons hospitalized, two of who were critically injured.

The El Paso Fire department responded to the accident, shut off the gas supply to the apartments, and rescued the victims still trapped in the rubble. The police department aided in the rescue efforts, cordoned off the site, and rerouted all traffic from the area.

The Southern Union Gas Company arrived at 6:45am and found gas venting from the base of a telephone pole andfrom a recent street excavation. Gas at explosive levels was discovered at the curb line adjacent toto the destroyed apartments and elsewhere in the areas. Three leaks were discovered ultimately in the 20 psig, 2 inch gas main which serviced the area: broken pipe threads in a cast-iron reducer at a 2-inch valve, a severe corrosion leak in the 2-inch main 21 feet away from the reducer, and a smaller pinhole leak still farther away.​

We determined that the probable cause of the explosion was the ignition of an accumulation of natural gas which had leaked primarily from a broken cast-iron reducer and to a lesser extent from two corrosion leaks in the distribution main. The gas migrated beneath the concrete road surface, permeated the area, entered the apartment complex via the crawl space, and was ignited by an undetermined source. The uncovering and disturbing of the cast-iron pipe by the gas company in an unsuccessful search for a gas leak 6 days before the accident contributed to the failure of the reducer.

The uncovering and disturbing of the cast-iron pipe by the gas company in an unsuccessful search for a gas leak 6 days before the accident contributed to the failure of the reducer.

Contributing to the loss of life and the property damage were the failure of the gas company to locate or to confirm positively the absence of a leak, and the failure of both the tenants and the apartment superintendent to notify either the gas company of the fire department of the gas odors which had been detected previously.  

​​​As a result of this investigation, we made​ the following safety recommendations.

To the Office of Pipeline Safety of the Department of Transportation:

• Amend 49 CFR 192   to require that cast-iron piping or fittings uncovered during construction or maintenance work in such a way as to weaken their support from below be replaced or reinforced to protect against outside forces which could cause failure. (P-74-10)
  
• ​Amend 49 CFR 192 ​.615 (D) to require that educational programs intended to enable customers and the general public to recognize and report gas emergncies be printed in English and Spanish and in other languages which a significant portion of the community speak and understand. (P-74-11)​

The American Society of Mechanical Engineers Gas Piping Standards Committee: Develop guidelines for pinpointing the location of reported gas leaks.These should include procedures to determine the degree of hazard that exists as a result of the reported leak. (P-74-12)

To the South Union Gas Company:

• Instruct the maintenance crews concerning the hazards of inadequate support during the filling of recently excavated piping facilities.(P-74-13)
  
• Improve followup procedures to assure that all reported leaks are located. (P-74-14)
  
• Initiate a program of instruction for gas customers and the general public concerning the potential hazards of natural gas. This program should include mailing flyers to customers which include names and telephone numbers to be used in emergencies and placing education material in the news media. This program should, where applicable, be bilingual to reach both the English and non-English speaking communities within the distribution systems (P-74-15)