NTSB Safety Recommendation P-73-008

NTSB safety recommendation P-73-008.

THE NTSB RECOMMENDS THAT THE NORTHERN STATES POWER COMPANY: DESIGNATE EMERGENCY VALVES IN ITS DISTRIBUTION SYSTEM TO PERMIT RAPID SHUTDOWN OF FAILED SECTIONS WITHOUT INTERRUPTING GAS SERVICE TO AN ENTIRE COMMUNITY.

Priority: CLASS II

Overall Status: Closed - Acceptable Action

Issued Date: 1973-05-16

Adopted Date: 1973-05-16

Overall Date Closed: 1976-09-10

Synopsis: On October 30, 1972, a bulldozer struck and snapped a 3/4-inch gas-service line in Lake City, Minn. A department store located near the rupture, but not served by gas, blew up and later caught fire. Six persons died as a result of the explosion and 10 more were injured. The Northern States Power Company (NSP) later unearthed the entire service line and discovered that in addition to being snapped by the bulldozer, the line had been pulled out of a compression coupling next to the main. Gas had permeated the soil, migrated into the department-store basement, accumulated, and exploded.

Ntsbnumber: PLD73XR001

Report Number: PAR-73-01

Addressee Name: Northern States Power Company

Addressee Status: Closed--No Longer Applicable

Addressee Date Closed: 1976-09-10

Addressee Acronym: NSP

Addressee Organization Type: P-Private Industry

Communication Date: 1973-07-20

Communication Type: Non-Recipient Correspondence

Communication Contents: THIS LETTER IS FROM THE DEPARTMENT OF TRANSPORTATION, NOT THE RECIPIENT OF THE RECOMMENDATION. THIS IS NON-RECIPIENT CORRESPONDENCE: -From Benjamin O. Davis, Jr., Assistant Secretary for Environment, Safety, and Consumer Affairs, Office of Pipeline Safety, United States Department of Transportation: We have reviewed your Pipeline Accident Report No. PAR-7 3·-1 on the October 30, 1972, incident at Lake City, Minnesota, and the recommendations included therein. With regard to the recommendations made to the Office of Pipeline Safety (OPS), we wish to advise that on April 30, 1973, a contract was awarded to the Mechanics Research Institute to conduct a study on the rapid shutdown of failed pipeline facilities and pressure limiting of pipeline systems. Included in the contract work will be a study of fail-safe devices as recommended in the National Transportation Safety Board (NTSB) recommendation No. P-73-2. This study will also relate to the number and location of emergency valves in high pressure distribution systems as recommended in recommendation No. P-73-4. This contract study is scheduled for completion in December 1973. The OPS will then evaluate the data obtained and take the appropriate action. We will keep you advised of the action taken in this regard. In addition, NTSB recommendation No. P-73-4 requests consideration for placing valve keys in the hands of local authorities. This portion of the recommendation is being considered in connection with the OPS's plan to clarify the intent of the requirements for operating and maintenance plans and emergency plans as outlined in our letter to you dated July 5, 1973. We agree with NTSB recommendation No. P-73-3 insofar as it recommends a review of the regulations relative to the uncertainty as to the conditions which permit the use of compression couplings. Such a review will shortly be initiated. To the extent that the review shows a need for amending Paragraph 192.367(b), rulemaking will be initiated. The OPS also concurs with the recommendations made by NTSB to the other parties of interest in this Lake City incident. The NTSB's recommendations No. P-73-5 to the Department of Labor and No. P-73-11 to the Department of Public Works of Lake City, Minnesota, will lend support to the OPS program to promote the Model Statute For The Protection of Underground Pipelines and Utilities. The NTSB recommendation No. P-73-·6 to the American Society of Mechanical Engineers Gas Piping Standards Committee (ASME) will support the OPS recommendation to that Society to develop guideline material on the location of emergency valves. The OPS has suggested to ASME that they include such guideline material in a supplement to the "ASME Guide For Gas Transmission and Distribution Pipeline Systems -1973." The recommendations Nos. P-73-7 through 10 to the Northern States Power Company all relate to areas that we are emphasizing in the OPS/State agencies pipeline safety seminars that are presently being conducted throughout the country. These areas will also be included in our considerations for clarifying the intent of the requirements for operating and maintenance plans and emergency plans as discussed in our letter of July 5. We greatly appreciate your pipeline accident investigation report and will continue to take the appropriate actions as indicated.

Addressee Acronym: NSP

Addressee Organization Type: P-Private Industry

Communication Date: 1976-06-01

Communication Type: Official Correspondence

Communication Contents: 5/21/76 - TELEPHONE CONVERSATION GENERAL MANAGER: NORTHERN STATES POWER COMPANY HAS DESIGNATED 1,000 ADDITIONAL VALVES AS EMERGENCY VALVES BRINGING THE TOTAL TO 1,129. 6/1/76 - LTR. FROM NSP COMPANY: NSP HAS MODIFIED ITS CRITERIA USED IN DESIGNATING CERTAIN DISTRIBUTION LINE VALVES AS EMERGENCY VALVES. ONE OF THE NEW CRITERIA EMPLOYED IS THAT EMERGENCY VALVES SHOULD PERMIT THE ISOLATION OF SECTIONS CONTAINING NO MORE THAN 700 CUSTOMERS ON THE LARGE SYSTEMS WITH A LOWER NUMBER ON THE SMALL SYSTEMS. TO ASSURE PROPER PERIODIC INSPECTION AND MAINTENANCE OF THESE EMERGENCY VALVES ALONG WITH CERTAIN OTHER INSPECTION WORK REQUIRED BY DOT REGULATIONS, NSP ADDED SIX FULL TIME EMPLOYEES IN 1973.