# NTSB Safety Recommendation P-74-046 **Citation:** P-74-046 **Type / status:** guidance / guidance **Agency:** National Transportation Safety Board **Effective:** 1974-10-24 **Published:** 1974-10-24 THE NTSB RECOMMENDS THAT THE AMERICAN GAS ASSOCIATION: STUDY THE NATURAL GAS PERMEATING AND MIGRATION PHENOMENA IN VARIOUS TYPES OF SOIL AND UNDER PAVED SURFACES. BASED ON THE RESULTS OF THIS STUDY, RECOMMEND THE USE OF CERTAIN TYPES OF SOIL FOR PIPELINE BACKFILL MATERIAL THAT WILL AID IN ALLOWING LEAKING GAS TO VENT TO THE ATMOSPHERE AT THE LEAK LOCATION WITH A MINIMUM PERMEATION OR MIGRATION EFFECT. ## Document text NTSB safety recommendation P-74-046. THE NTSB RECOMMENDS THAT THE AMERICAN GAS ASSOCIATION: STUDY THE NATURAL GAS PERMEATING AND MIGRATION PHENOMENA IN VARIOUS TYPES OF SOIL AND UNDER PAVED SURFACES. BASED ON THE RESULTS OF THIS STUDY, RECOMMEND THE USE OF CERTAIN TYPES OF SOIL FOR PIPELINE BACKFILL MATERIAL THAT WILL AID IN ALLOWING LEAKING GAS TO VENT TO THE ATMOSPHERE AT THE LEAK LOCATION WITH A MINIMUM PERMEATION OR MIGRATION EFFECT. Priority: CLASS II Overall Status: Closed - Acceptable Alternate Action Issued Date: 1974-10-24 Adopted Date: 1974-10-24 Overall Date Closed: 1983-03-31 Synopsis: ON JUNE 23, 1973, A SERIES OF EXPLOSIONS, FOLLOWED BY FIRE, OCCURRED AT 12321 WELLING LANE IN BOWIE, MARYLAND. THREE OCCUPANTS OF THE HOUSE WERE KILLED, AND A FOURTH WAS INJURED; THE HOUSE WAS BADLY DAMAGED. HOUSES IN A FIVE-BLOCK AREA WERE EVACUATED. Ntsbnumber: PLD73XR006 Report Number: PAR-74-05 Addressee Name: American Gas Association Addressee Status: Closed--No Longer Applicable Addressee Date Closed: 1983-03-31 Addressee Acronym: AGA Addressee Organization Type: A-Associations Communication Date: 1975-03-31 Communication Type: Official Correspondence Communication Contents: PHONE CONVERSATION WITH THE AMERICAN GAS ASSOCIATION ON 3/31/75: ON MARCH 19, 1975, THE AMERICAN GAS ASSOCIATION (AGA) AUTHORIZED $170,000 FOR THE FIRST YEAR OF A THREE YEAR STUDY OF THE PROBLEM OF GAS ODORIZATION. Addressee Acronym: AGA Addressee Organization Type: A-Associations Communication Date: 1979-11-16 Communication Type: Official Correspondence Communication Contents: AGA LTR: SAFETY RECOMMENDATION BEING ADDRESSED IN GAS RESEARCH INSTITUTE RESEARCH PROGRAM. Addressee Acronym: AGA Addressee Organization Type: A-Associations Communication Date: 1983-01-26 Communication Type: Official Correspondence Communication Contents: GAS RESEARCH INSTITUTE LETTER: AN ASSESSMENT OF GAS INDUSTRY ODORIZATION AREAS WHERE RESEARCH MONEY COULD BE BETTER ALLOCATED THAN DEVELOPING A "PERFECT" ODORANT OR SELECTING A NON-ADSORBENT BACKFILL MATERIAL (NTSB RECOMMENDATION NO. P-74-46). THESE ARE: (1) DETERMINATION OF THE "APPROPRIATE" LEVEL FOR ODORIZATION. THE D.O.T. ODORIZATION STANDARD IS VAGUE AND THE INDUSTRY PRACTICE VARIES FROM ONE UTILITY TO ANOTHER. THERE IS ALSO A NEED TO IMPROVE UNDERSTANDING OF OLFACTORY FATIGUE AND THE MASKING OF GAS ODORANTS BY OTHER ODORS; (2) DEVELOPMENT OF IMPROVED ODORANT CONCENTRATION MEASURING INSTRUMENTS THAT ARE RUGGED, ACCURATE, INEXPENSIVE, SIMPLE TO OPERATE AND WHICH ARE NOT DEPENDENT ON THE HUMAN OLFACTORY SENSE; (3) DEVELOPMENT OF SMALL ODORANT INJECTION EQUIPMENT THAT ARE RELIABLE AND REQUIRE LITTLE MAINTENANCE. GRI HAS EMBARKED UPON A MAJOR RESEARCH PROGRAM TO ADDRESS THE FIRST TWO OF THESE AREAS BECAUSE WE FELT THAT THEY HAD THE GREATEST PRIORITY. WE ARE WELL ON OUR WAY TO COMPLETION OF THE FIRST STUDY. THREE DIFFERENT APPROACHES FOR ODORANT INSTRUMENT DESIGN ARE BEING ADDRESSED IN THE SECOND AREA. ALL THE APPROACHES BEING CONSIDERED ARE NOT DEPENDENT ON THE HUMAN OLFACTORY SENSE--A MAJOR PROBLEM WITH THE FIELD INSTRUMENTS USED TODAY. WE BELIEVE THAT THESE STUDIES ARE FULLY RESPONSIVE TO NTSB RECOMMENDATION P-74-44. WE ANTICIPATE THAT THE DEVELOPMENT OF A SMALL ODORANT INJECTION DEVICE WILL BE INITIATED IN 1984. Addressee Acronym: AGA Addressee Organization Type: A-Associations Communication Date: 1980-02-14 Communication Type: Official Correspondence Addressee Acronym: AGA Addressee Organization Type: A-Associations Communication Date: 1979-01-02 Communication Type: Official Correspondence Addressee Acronym: AGA Addressee Organization Type: A-Associations Communication Date: 1979-10-31 Communication Type: Official Correspondence Addressee Acronym: AGA Addressee Organization Type: A-Associations Communication Date: 1983-03-31 Communication Type: Official Correspondence ## Provenance - Official: Yes - Source: - Source ID: `ntsb-pipeline` - SHA-256: `bd93fb6f686fbd2d693e8b6b3d67e8b524cf7255cd787411feb445fd90ed08ef` - Retrieved: 2026-08-20T04:57:24.741Z - Exported: 2026-08-23T23:31:13.245Z - Document slug: `ntsb-recommendation-p-74-046` ### Source metadata ```json { "recordKind": "ntsb_safety_recommendation", "safetyRecommendationNumber": "P-74-046", "recommendationMode": "Pipeline", "topicMode": "Pipeline", "ntsbNumber": "PLD73XR006", "priority": "CLASS II", "overallStatus": "Closed - Acceptable Alternate Action", "overallStatusAcronym": "CAAA", "overallDateClosed": "1983-03-31", "lastModifiedDate": "2016-11-15", "reportNumber": "PAR-74-05", "reportUrl": "https://www.ntsb.gov/investigations/Pages/PLD73XR006.aspx", "transmittalLetterUrl": "http://www.ntsb.gov/safety/safety-recs/recletters/P74_37_49.pdf", "addressees": [ { "addresseeName": "American Gas Association", "addresseeStatusAcronym": "CNLA", "addresseeStatus": "Closed--No Longer Applicable", "addresseeDateClosed": "1983-03-31", "addresseeDetails": [ { "addresseeAcronym": "AGA", "addresseeOrganizationType": "A-Associations", "isFromNtsb": false, "communicationDate": "1975-03-31", "communicationType": "Official Correspondence", "communicationContents": "PHONE CONVERSATION WITH THE AMERICAN GAS ASSOCIATION ON 3/31/75: ON MARCH 19, 1975, THE AMERICAN GAS ASSOCIATION (AGA) AUTHORIZED $170,000 FOR THE FIRST YEAR OF A THREE YEAR STUDY OF THE PROBLEM OF GAS ODORIZATION." }, { "addresseeAcronym": "AGA", "addresseeOrganizationType": "A-Associations", "isFromNtsb": false, "communicationDate": "1979-11-16", "communicationType": "Official Correspondence", "communicationContents": "AGA LTR: SAFETY RECOMMENDATION BEING ADDRESSED IN GAS RESEARCH INSTITUTE RESEARCH PROGRAM." }, { "addresseeAcronym": "AGA", "addresseeOrganizationType": "A-Associations", "isFromNtsb": false, "communicationDate": "1983-01-26", "communicationType": "Official Correspondence", "communicationContents": "GAS RESEARCH INSTITUTE LETTER: AN ASSESSMENT OF GAS INDUSTRY ODORIZATION AREAS WHERE RESEARCH MONEY COULD BE BETTER ALLOCATED THAN DEVELOPING A \"PERFECT\" ODORANT OR SELECTING A NON-ADSORBENT BACKFILL MATERIAL (NTSB RECOMMENDATION NO. P-74-46). THESE ARE: (1) DETERMINATION OF THE \"APPROPRIATE\" LEVEL FOR ODORIZATION. THE D.O.T. ODORIZATION STANDARD IS VAGUE AND THE INDUSTRY PRACTICE VARIES FROM ONE UTILITY TO ANOTHER. THERE IS ALSO A NEED TO IMPROVE UNDERSTANDING OF OLFACTORY FATIGUE AND THE MASKING OF GAS ODORANTS BY OTHER ODORS; (2) DEVELOPMENT OF IMPROVED ODORANT CONCENTRATION MEASURING INSTRUMENTS THAT ARE RUGGED, ACCURATE, INEXPENSIVE, SIMPLE TO OPERATE AND WHICH ARE NOT DEPENDENT ON THE HUMAN OLFACTORY SENSE; (3) DEVELOPMENT OF SMALL ODORANT INJECTION EQUIPMENT THAT ARE RELIABLE AND REQUIRE LITTLE MAINTENANCE. GRI HAS EMBARKED UPON A MAJOR RESEARCH PROGRAM TO ADDRESS THE FIRST TWO OF THESE AREAS BECAUSE WE FELT THAT THEY HAD THE GREATEST PRIORITY. WE ARE WELL ON OUR WAY TO COMPLETION OF THE FIRST STUDY. THREE DIFFERENT APPROACHES FOR ODORANT INSTRUMENT DESIGN ARE BEING ADDRESSED IN THE SECOND AREA. ALL THE APPROACHES BEING CONSIDERED ARE NOT DEPENDENT ON THE HUMAN OLFACTORY SENSE--A MAJOR PROBLEM WITH THE FIELD INSTRUMENTS USED TODAY. WE BELIEVE THAT THESE STUDIES ARE FULLY RESPONSIVE TO NTSB RECOMMENDATION P-74-44. WE ANTICIPATE THAT THE DEVELOPMENT OF A SMALL ODORANT INJECTION DEVICE WILL BE INITIATED IN 1984." }, { "addresseeAcronym": "AGA", "addresseeOrganizationType": "A-Associations", "isFromNtsb": true, "communicationDate": "1980-02-14", "communicationType": "Official Correspondence", "communicationContents": "" }, { "addresseeAcronym": "AGA", "addresseeOrganizationType": "A-Associations", "isFromNtsb": true, "communicationDate": "1979-01-02", "communicationType": "Official Correspondence", "communicationContents": "" }, { "addresseeAcronym": "AGA", "addresseeOrganizationType": "A-Associations", "isFromNtsb": true, "communicationDate": "1979-10-31", "communicationType": "Official Correspondence", "communicationContents": "" }, { "addresseeAcronym": "AGA", "addresseeOrganizationType": "A-Associations", "isFromNtsb": true, "communicationDate": "1983-03-31", "communicationType": "Official Correspondence", "communicationContents": "" } ] } ], "jurisdiction": "US" } ```