NTSB Safety Recommendation P-15-037

NTSB safety recommendation P-15-037.

TO CONSOLIDATED EDISON COMPANY OF NEW YORK, INC.: Extend your gas main isolation valve installation program to include strategic locations where long distribution mains currently cannot be isolated, giving priority to pipelines in more densely populated areas.

Priority: CLASS II

Overall Status: Closed - Acceptable Action

Issued Date: 2015-06-29

Adopted Date: 2015-06-09

Overall Date Closed: 2017-12-01

Synopsis: On March 12, 2014, about 9:30 a.m. eastern daylight time, two adjacent multiuse five-story buildings were destroyed by a natural gas-fueled explosion and resulting fire. The buildings were situated on the west side of Park Avenue between East 116th Street and East117th Street in the East Harlem district of the Borough of Manhattan in New York City. The violent explosion damaged buildings on the east and west sides of Park Avenue and along East116th and East 117th Streets. The Metro-North Railroad suspended rail service for about 71/2 hours on the elevated railway along Park Avenue because of debris from the explosion on the track. Eight people died, more than 50 people were injured, and more than 100 families were displaced from their homes as a result of this accident. The cost to Consolidated Edison Company of New York, Inc. (ConEdison), of equipment damages, emergency response activities, remediation, and replacement exceeded $1.9 million.

Probable Cause: The National Transportation Safety Board determines that the probable cause of the accident was (1) the failure of the defective fusion joint at the service tee, installed by Consolidated Edison Company of New York, Inc., in 2011, that allowed natural gas to leak from the gas main and migrate into the building where it ignited and (2) a breach in the sewer line that went unrepaired by the New York City Department of Environmental Protection since at least 2006 that allowed groundwater and soil to flow into the sewer, resulting in a loss of support for the gas main, which caused the line to sag and overstressed the defective fusion joint.

Ntsbnumber: DCA14MP002

Report Number: PAR-15-01

Addressee Name: Consolidated Edison (Con Ed)

Addressee Status: Closed - Acceptable Action

Addressee Date Closed: 2017-12-01

Addressee Acronym: Con Ed

Addressee Organization Type: P-Private Industry

Communication Date: 2017-04-07

Communication Type: Official Correspondence

Communication Contents: On December 21, 2015, based on information provided in your September 25, 2015, letter, Safety Recommendations P-15-34 and -37 were classified OPEN--ACCEPTABLE RESPONSE. To date, we have not received any further updates regarding your actions to address these recommendations.

Addressee Acronym: Con Ed

Addressee Organization Type: P-Private Industry

Communication Date: 2017-12-01

Communication Type: Official Correspondence

Communication Contents: We note that you have accelerated your main replacement program to 100 miles per year. Isolation valves are installed in this program in accordance with your specifications, which leads to an increase in the number of installed valves. The main replacement program, which targets cast iron and unprotected steel pipe, uses a prioritization model that now includes population density as a consequence factor; this will result in the accelerated installation of isolation valves in more densely populated areas. You have also developed a 5-year program to install isolation valves near critical customers, such as hospitals, nursing homes, schools, and daycare centers. We note that your program has identified 521 of these sensitive customers. We further note that, in collaboration with the GTI, you have initiated the third phase of your emergency main stop-off station (EMSOS), which uses access tubes installed on the gas main to insert inflatable stoppers to add isolation points on larger-diameter gas distribution mains. You plan to use the EMSOS to add isolation points on larger-diameter mains not planned for replacement, which will make more isolation points available sooner. Revising your prioritization models to consider population densities and critical customers, and your work developing and using the EMSOS to quickly increase the number of isolation points, satisfy Safety Recommendation P-15-37, which is classified CLOSED--ACCEPTABLE ACTION.

Addressee Acronym: Con Ed

Addressee Organization Type: P-Private Industry

Communication Date: 2015-12-21

Communication Type: Official Correspondence

Communication Contents: We understand that, by the end of this year, you plan to install more than 2,800 isolation valves on your gas distribution system during the installation of new and/or replacement gas mains. We note that you also plan to increase the number of isolation valves installed on your gas distribution system from the current 45,000 (more than 17,000 of which are installed on your low pressure system) by over 3,500 annually. We support your planned expansion of the program to implement a series of additional initiatives and program enhancements over the next several years that will exceed federal and state code requirements for isolation valves on low pressure natural gas distribution systems. Your plans, when completed, will satisfy Safety Recommendation P-15-37, which is classified OPEN—ACCEPTABLE RESPONSE. We would appreciate receiving periodic updates as you progress toward your goals.

Addressee Acronym: Con Ed

Addressee Organization Type: P-Private Industry

Communication Date: 2017-05-01

Communication Type: Official Correspondence

Communication Contents: Marc E. Huestis, Senior Vice President: In both 2015 and 2016, Con Edison installed more than 2,800 isolation valves annually. As we continue to accelerate our main replacement program to 100 miles per year, we will continue to install valves in accordance with our specifications and the number of isolation valves installed will accordingly increase. Our main replacement prioritization model used to priorit ize the replacement of cast iron and unprotected steel pipe now includes population density as a consequence factor. This will accelerate the installation of isolation valves in more densely populated areas. Con Edison has also developed a five year program to install isolation valves near critical customers that was approved by the New York State Public Service Commission. The program identifies 521 critical and sensitive cu stomers, which includes hospitals, nursing homes, schools and daycare centers. Finally, Con Edison's Research and Development (R&D) Department and the Gas Technology Institute (GTI) initiated Phase 3 of the Emergency Main Stop-off Station {EMSOS) project in October 2016. The EMSOS project team has developed a system that uses access tubes installed on the gas main to insert inflatable stoppers as a means of adding isolation points on larger diameter gas distribution mains. The Company plans to use EMSOS to add isolation points on larger diameter mains not planned for replacement. The first two phases focused on developing the prototype system. The third phase of this project that is currently under way, is focused on creating training documents, conducting crew training, developing O&M procedures and engineering diagrams, performing field installations, and fully commercializing the unit.

Addressee Acronym: Con Ed

Addressee Organization Type: P-Private Industry

Communication Date: 2015-09-25

Communication Type: Official Correspondence

Communication Contents: -From Craig S. Ivey, President: In 2015, Con Edison will install more than 2,800 isolation valves on its gas distribution system during the installation of new and/or replacement gas mains. As a result of our plans to accelerate our cast iron and unprotected steel gas main replacement program, we will increase the number of isolation valves installed to over 3,500 annually. Currently, there are more than 45,000 isolation valves on the Con Edison gas distribution system, of which more than 17,000 are installed on the low pressure system. To further expand this program, Con Edison wi ll implement the following additional initiatives and program enhancements, which exceed federal and state code requirements for isolation valves on low pressure natural gas distribution systems: 1. Con Edison will install isolation valves on new and replaced mains that are specifically targeted for strategic locations in densely populated areas by changing the algorithm in the model that is used to prioritize the replacement of cast iron and unprotected steel. Currently, the Company's Main Replacement Prioritization (MRP) models for cast iron and unprotected steel are based on the likelihood of a future leak. The unprotected steel model incorporates factors such as physical parameters and condition (e.g. , diameter, age), previous failure history, and the area surrounding the main (e.g., soil condition). The cast iron prioritization model incorporates risk and consequence factors (e.g. gas ingress), in addition to the condition-based variables utilized in the unprotected steel model. Con Edison is reviewing enhancements to its MRP model that will include integrating population density as a consequence factor. Other factors that may be added include ease of leak migration, likelihood of gas release, street depressions (e.g., traffic loading), pre-1972 vintage steel services, and third party activity. Incorporating factors such as population density, traffic loading and third party activity into our MRP model is designed to accelerate the installation of isolation valves in more densely populated areas. This effort will also improve alignment of our replacement program with our Distribution Integrity Management Plan (DIMP) by focusing on specific risks such as older, pre-1972 vintage steel services. 2. Over a five year period, Con Edison will install valves to isolate sections of gas main which serve critical and sensitive gas customers. Utilizing the Company's Emergency Management Critical and Sensitive Customer list, (which includes hospitals, schools, day care and senior care centers), the Company performed a preliminary engineering analysis that determined over 1,000 valves would be required to isolate the critical and sensitive gas customers on the list. In addition to the 3,500 isolation valves that will be installed annually as part of the Main Replacement Program (as described in item #1 above), the Company will implement a 5-year program that is designed to specifically isolate critical and sensitive gas customers. This program is intended to address critical and sensitive gas customer locations where isolation valves are not already installed, or would not be installed as part of the MRP Program. The list of critical and sensitive gas customers will be reviewed and updated annually. Subsequent program changes will be made (as necessary) based upon an engineering analysis. 3. Con Edison will continue to work with the Gas Technology Institute (GTI) on a Research and Development (R&D) project designed to facilitate rapid and rel iable isolation of 16" diameter and larger low pressure cast iron and steel gas mains. This project is exploring the use of balloon stoppers that can be quickly inserted and inflated in the gas main when needed. This type of equipment, which is not yet commercially available, is intended to provide a much more cost-effective option for the isolation of large diameter mains than the installation of isolation valves. Con Edison would install special no-blow fittings on 16" diameter and larger low pressure cast iron and steel gas mains, along with a plastic riser that would provide access from a valve box installed at the road surface. If isolation becomes necessary, the riser can be accessed from the street where a gas crew can quickly remove the completion plug in the fitting and install balloon stoppers to effectively isolate the main and quickly stop the leaking gas. This method of isolation is designed to be completed in 30 minutes compared to the 4 to 8 hours needed to excavate, tap, and stop off the main using conventional methods at typical locations that do not have isolation valves. A more detailed overview of this R&D technology is provided as Appendix B. During the investigation we proposed findings and conclusions, some of which differed significantly from the final findings and conclusions issued by the NTSB. We continue to carefully review the complete NTSB Report. If we identify additional factual bases for reaching materially different conclusions, we will raise those issues with NTSB staff. We share the NTSB's commitment to gas pipeline safety and will implement the recommendations to further improve the safety of our system. We will provide periodic updates on our progress.