Skip Ribbon Commands
Skip to main content
Safety Recommendation Details

Safety Recommendation P-70-037
Details
Synopsis: ON NOVEMBER 6, 1969, DURING A HIGHWAY CONSTRUCTION PROJECT IN BURLINGTON, IOWA, A BULLDOZER WEIGHING 70,000 POUNDS DROVE OVER AND PARTIALLY COLLAPSED THE STEEL COVERS OF A GAS REGULATOR PIT, DAMAGING THE REGULATOR. WHILE THE PRESSURE WAS PARTIALLY CONTROLLED BY A MONITORING OR SAFETY REGULATOR, GAS, REPORTEDLY AT FOUR TO FIVE TIMES THE NORMAL OPERATING PRESSURE, ENTERED THE DISTRIBUTION SYSTEM. GAS CUSTOMERS IN THE AFFECTED AREA STARTED REPORTING HIGH GAS PILOTS AND FIRES TO ISU AND THE FIRE DEPARTMENT. THE HIGH-PRESSURE GAS SOURCE WAS TURNED OFF BUT FIRES CONTINUED TO BE REPORTED, THE FIRES WROUGHT MAJOR DAMAGE TO THE INTERIORS OF 10 HOUSES AND MINOR DAMAGE TO KITCHENS AND APPLIANCES IN 42 OTHERS. PROPERTY DAMAGE WAS ESTIMATED AT $80,000.
Recommendation: THE NTSB RECOMMENDS THAT IOWA SOUTHERN UTILITIES, INC., TAKE THE FOLLOWING ACTION: REVIEW ITS OWN REGULATOR DESIGN, MAINTENANCE, AND TRAINING PROCEDURES TO DETERMINE WHETHER ITS GAS CONSUMERS WILL BE PROPERLY PROTECTED AGAINST OVERPRESSURIZATION IN THE EVENT OF A MALFUNCTION OF A PRIMARY REGULATOR.
Original recommendation transmittal letter: PDF
Overall Status: Closed - Acceptable Action
Mode: Pipeline
Location: Burlington, IA, United States
Is Reiterated: No
Is Hazmat: No
Is NPRM: No
Accident #: DCA70MP001
Accident Reports:
Low Pressure Natural Gas Distribution System
Report #: PAR-70-01
Accident Date: 11/6/1969
Issue Date: 10/14/1970
Date Closed: 7/20/1976
Addressee(s) and Addressee Status: Iowa Southern Utilities, Inc. (Closed--No Longer Applicable)
Keyword(s): Maintenance, Training and Education

Safety Recommendation History
From: Iowa Southern Utilities, Inc.
To: NTSB
Date: 7/7/1971
Response: THE BOARD WAS INFORMED BY LETTER THAT THE FOLLOWING ACTION HAS BEEN TAKEN: AN ENGINEERING CONSULTANT WAS HIRED TO MAKE A STUDY OF REGULATOR STATIONS ON THE LOW PRESSURE SYSTEM IN BURLINGTON, IOWA, AND TO MAKE RECOMMENDATIONS TO PROPERLY PROTECT THE SYSTEM AGAINST OVERPRESSURIZATION AND RECOMMENDED SET POINTS OF MONITOR REGULATORS. MONITOR REGULATORS ON THE SYSTEM WERE PILOT LOADED TO PROVIDE MORE SENSITIVE CONTROL UPON FAILURE OF WORKING REGULATORS. AN OVERPRESSURE WARNING DEVICE WAS INSTALLED AND LOCATED IN THE DISPATCHING OFFICE. CONCRETE-FILLED STEEL POSTS HAVE BEEN INSTALLED AROUND BOTH REGULATOR PITS FOR ADDED PROTECTION. THE CONTROL LINE TO THE MONITOR REGULATOR HAS BEEN RELOCATED OUTSIDE THE REGULATOR PIT AND AT A LOWER DEPTH. CORRESPONDENCE DOCUMENTATION INCOMPLETE.

From: NTSB
To: Iowa Southern Utilities, Inc.
Date: 6/2/1971
Response: