NTSB Safety Recommendation P-83-016

NTSB safety recommendation P-83-016.

THE NTSB RECOMMENDS THAT THE MONTANA POWER COMPANY: INSPECT EACH CUSTOMER METER INSTALLATION TO DETERMINE IF A HIGH PRESSURE GAS SERVICE LINE IS INSTALLED BENEATH A BUILDING AND, WHERE THE CONDITION EXISTS, REROUTE ALL HIGH PRESSURE PIPING TO AN OUTSIDE LOCATION.

Priority: CLASS II

Overall Status: Closed - Acceptable Action

Issued Date: 1983-07-08

Adopted Date: 1983-06-24

Overall Date Closed: 1995-07-12

Synopsis: ON NOVEMBER 15, 1982, A NATURAL GAS EXPLOSION IN CONRAD, MONTANA, DEMOLISHED ONE HOUSE, HEAVILY DAMAGED AN ADJACENT HOUSE, EXTENSIVELY DAMAGED NEARBY HOUSES, AND INJURED ONE PERSON. NATURAL GAS ESCAPING FROM A DISCONNECTED GAS PIPE LOCATED BENEATH THE HOUSE FILLED THE ENCLOSED CRAWL SPACE AND IGNITED WHEN THE OWNER, WHO WAS AT AN INSIDE ENTRANCE TO THE CRAWL SPACE, LIT A PROPANE TORCH WHICH HE HAD PLANNED TO USE TO THAW FROZEN WATER PIPES LOCATED BENEATH THE HOUSE.

Probable Cause: None

Ntsbnumber: DCA83FP006

Report Number: None

Addressee Name: Montana Power Company

Addressee Status: Closed - Acceptable Action

Addressee Date Closed: 1995-07-12

Addressee Acronym: MPC

Addressee Organization Type: P-Private Industry

Communication Date: 1995-07-12

Communication Type: Official Correspondence

Communication Contents: THE BOARD UNDERSTANDS THAT THE MPC HAS COMPLETED A PROGRAM TO "MOVE ALL GAS METERS OUTSIDE & ELIMINATE ALL INSTANCES WHERE DISTRIBUTION PRESSURE (20 PSIG) EXISTS INSIDE THE BASEMENTS & CRAWL SPACES UNDER BUILDINGS." BASED ON YOUR REPORTED ACTIONS, P-83-16 HAS BEEN CLASSIFIED "CLOSED--ACCEPTABLE ACTION."

Addressee Acronym: MPC

Addressee Organization Type: P-Private Industry

Communication Date: 1983-07-15

Communication Type: Official Correspondence

Communication Contents: MONTANA POWER COMPANY LETTER: IN RESPONSE TO YOUR LETTER, WE ARE FORMULATING AN INSPECTION PROGRAM TO REVIEW OUR SYSTEM FOR CONDITIONS SIMILAR TO THOSE OF THE CONRAD INCIDENT. WE WILL CONSIDER THE FEASIBILITY OF CONDUCTING THIS INSPECTION IN CONJUNCTION WITH OUR ESTABLISHED ANNUAL LEAK DETECTION PROGRAM.

Addressee Acronym: MPC

Addressee Organization Type: P-Private Industry

Communication Date: 1995-04-12

Communication Type: Official Correspondence

Communication Contents: MONTANA POWER COMPANY HAS COMPLETED A PROGRAM IN CONRAD MONTANA, TO MOVE ALL GAS METERS OUTSIDE & ELIMINATE ALL INSTANCES WHERE DISTRIBUTION PRESSURE (20 PSIG) EXISTS INSIDE THE BASEMENTS & CRAWL SPACE UNDER BUILDINGS. WE FEEL THAT WITH THE COMPLETION OF THIS PROGRAM, IN ADDITION TO THE ON-GOING SURVEILLANCE OF OUR GAS DISTRIBUTION SYSTEM, WE HAVE VIRTUALLY ELIMINATED THE CONDITIONS THAT COULD CONTRIBUTE TO A SIMILAR INCIDENT. AS MENTIONED IN THE ORIGINAL REPORT, MONTANA POWER COMPANY PURCHASED THIS SYSTEM IN 1953. WHILE INSIDE METER SETS ARE STANDARD PRACTICE IN MANY AREAS, HAVING DISTRIBUTION PRESSURE IN BUILDINGS PRESENTS AN OPPORTUNITY FOR A HIGH VOLUME LEAK THAT DOES NOT EXIST WHEN ONLY LOW PRESSURE IS SUPPLIED TO INSIDE PIPING.

Addressee Acronym: MPC

Addressee Organization Type: P-Private Industry

Communication Date: 1983-08-23

Communication Type: Official Correspondence