Consumers Energy Company Wayne Pipeline Failure and Explosion

Michigan Public Service Commission

Staff Investigation Report

Consumers Energy Company Wayne Pipeline Failure and Explosion

2945 South Wayne Road, Wayne

Incident Date: December 29, 2010

Case: 136015

Report Date: August 8, 2013

Staff Investigation Report – Consumers Energy Company Wayne Pipeline Failure and Explosion December 29, 2010

of 27

Table of Contents Operator, Location, & Consequences 3 Executive Summary 4 System Details 4 Events Leading up to the Failure 4 Emergency Response 5 Summary of Return-to-Service 7 Investigation Details 8 Findings and Contributing Factors 25 Appendices

A - Maps B - NRC Report C - Consumers Energy Incident Report to PHMSA D - Consumers Energy Procedures and Records E - MPSC Staff Interview Notes F - Laboratory Testing and Expert Analysis G - Consumers Energy Incident Investigation Report


of 27

MPSC Michigan Public Service Commission

Principal Investigators Brian Mills, Heather David

Program Manager David Chislea

Date of Report August 8, 2013

Subject Staff Investigation Report – Consumers Energy Company Wayne Pipeline Failure and Explosion

Case 136015

Operator, Location, & Consequences

Date of Failure 12/29/2010

Commodity Released Natural Gas

City/County & State City of Wayne, Wayne County, Michigan

OpID & Operator Name 2748, Consumers Energy Company

Unit Name Wayne Distribution

Milepost / Location 2945 South Wayne Road1

Type of Failure Pipeline leak / Outside force damage

Fatalities 2

Injuries 2

Description of Area Impacted

The area impacted is bound by Wayne Road to the west, Glenwood Road to the north, Second Street to the east, and Chestnut Street to the south. The area contains business and residential structures.

Estimated Damages $2,573,000

1 The explosion occurred at 2945 South Wayne Road. The failed main was located at 35018 Chestnut Street.


of 27

Executive Summary

On Wednesday, December 29, 2010, at 9:05 a.m., a natural gas explosion and fire occurred at the William C. Frank’s Furniture Store located at 2945 South Wayne Road in Wayne, Michigan. The explosion resulted in the death of two employees inside the building and injuries to one employee inside the building and one driver of a vehicle passing by at the time of the explosion. The business was destroyed and numerous other structures were damaged, including businesses, residences, and motor vehicles. Property damage and losses are estimated to be $2,573,000. The volume of gas unintentionally released as a result of the incident is estimated to be 600 thousand cubic feet.

The Michigan Public Service Commission Staff determines that the explosion occurred after natural gas migrated into the building from a main separation at a threaded joint on a two-inch bare steel, threaded and coupled distribution main, owned and operated by Consumers Energy Company (Consumers). The leak was approximately 233 feet east of the structure at 2945 South Wayne Road, and a manhole connected to an eight-inch sanitary sewer main was in close proximity to the gas main leak. The location and condition of the manhole allowed gas to permeate into the sanitary sewer system and into the building through a non-watertight sewer trap.

The Michigan Public Service Commission Staff determines that the probable cause of the pipeline leak was outside force damage resulting from material overload condition caused by external forces applied to the pipe. Contributing to the failure was construction of a residential fence with footings that rested on the affected gas main and construction of a sanitary system and manhole near the affected gas main. Potentially contributing to the failure was the construction of a poured concrete wall that encased the affected gas main and a reported sinkhole in the vicinity of the main failure. Contributing to the severity of the incident was the migration of gas into the sanitary sewer system and inadequate leak response by the operator.

System Details

The Wayne Distribution unit operated by Consumers Energy’s Distribution Operations is composed of distribution and transmission facilities. The section of pipe where the failure occurred, which provides service to residential and commercial customers, was two-inch bare steel main installed in 1940. It was threaded and coupled and cathodically unprotected. The pipe specification was API 5L and the pipe manufacturer was unknown. The maximum allowable operating pressure (MAOP) of this section was 60 pounds per square inch gauge (psig). Refer to Appendix A-1 for the Consumers Energy Area Gas Map showing the pipeline system of the area affected by the pipeline failure and explosion.

Events Leading up to the Failure

Prior to the pipeline failure, the system was operating at approximately 57 psig; no significant changes in pressure were detected prior to failure. As measured at Detroit Metropolitan airport, the temperature was approximately 21°F, the wind was generally from the south or southwest direction with a speed of approximately four to seven miles per hour, and there was no precipitation.


of 27

At 6:13 a.m. on December 29, 2010, a gas leak call from 34924 Chestnut Street was received by Consumers Energy. At 6:40 a.m. a Consumers Energy employee arrived onsite to investigate the complaint and spoke to the resident who made the leak complaint. The occupant indicated that gas odor was detected in the backyard, but not inside the house. The Consumers Energy employee conducted leak investigation consistent with Consumers Energy’s standard procedures, including free air reads taken inside the house, bar-hole testing conducted at the service riser of the meter, shadow testing performed on the meter, and inspection of meter fittings with gas detector, but the employee did not detect any odor, positive readings, or unusual flows of natural gas. The employee also investigated a manhole located on Chestnut Street and the houses located at 34914 and 34934 Chestnut Street, where there were no positive readings for the presence of gas. The employee checked the meter manifold for leaks at a house located across the street, but also found no positive readings. The employee informed the occupant of 34924 Chestnut Street of the results of the leak investigation and then proceeded to drive through the area in the Consumers Energy vehicle with the windows down. By 7:00 a.m. the employee left the area and a work order was completed indicating that no gas leaks were detected, although gas was occasionally detected by sense of smell in the atmosphere. Refer to Appendix D-1 for records related to the first leak call.

At 7:40 a.m. a second gas leak call from 34650 Chestnut Street was received by Consumers Energy. At 8:02 a.m. a second employee arrived onsite to investigate the complaint and found that the City of Wayne Fire Department had already responded to a separate gas odor complaint placed by the City of Wayne Department of Public Works. After speaking with the Fire Department briefly, the employee knocked on the house from which the leak call was received; however, there was no response. The employee took air reads at various locations around the house without any positive readings for the presence of gas. The employee then returned to the Consumers vehicle to determine the main location and retrieve equipment for bar-hole testing. Bar-hole testing was completed at the meter and then behind the alleyway of 34650 Chestnut Street at the approximate location where the service connected to the main; there were no positive readings for presence of gas nor did the employee smell gas at either of these locations. The employee continued bar-hole testing at various locations along the main west of 34650 Chestnut Street. There were again no positive readings for gas; however, the employee sporadically detected natural gas by sense of smell in the atmosphere. The employee then took air readings while driving the Consumers vehicle westward, consistent with the direction of the wind, down Chestnut Street. Again, the gas detector had no positive reads for gas, but the employee continued to detect odor in the air. The employee took air reads in the alleyway behind 2945 South Wayne Road, but did not receive any positive reads or detect the smell of gas in that location. The employee contacted supervisor to authorize a request for support with a mobile leak detection unit; however, the explosion occurred before the mobile unit was dispatched. Refer to Appendix D-2 for records related to the second leak call.

Emergency Response

At 9:05 a.m. the explosion occurred at 2945 South Wayne Road. Consumers Energy personnel responded in accordance with its Gas Emergency Manual. The Consumers Energy employee investigating the second leak call heard the explosion and notified the Field Leader, who then mobilized Consumers Energy’s first responders.


of 27

Telephonic notification of the incident was made to the Michigan Public Service Commission Staff at 9:59 a.m. and to the National Response Center at 10:29 a.m. MPSC and PHMSA staff responded onsite the incident. Refer to Appendix B for the National Response Center report, Appendix C for the Consumers Energy Incident Report to PHMSA, and Appendix D-3 for the Consumers Energy Incident Investigation Report submitted to MPSC Staff.

Personnel from the City of Wayne Fire Department heard the explosion from their station located a short distance away and arrived onsite at approximately 9:08 a.m., followed by additional responders from numerous local agencies providing Command and Control, Fire, Police, Medical, Search and Rescue, Investigation, and other emergency response functions related to the incident. Staff’s review of the incident report from the City of Wayne Fire Department indicated that early responding personnel noted that the area smelled of natural gas and that gas was leaking from the meter, which had sustained damage from the explosion.

Consumers distribution employees arrived onsite beginning at approximately 9:20 a.m. In order to obtain shutdown and flow control, Consumers crews conducted leak surveys to locate the source of the gas leak. Remote Methane Leak Detector (RMLD) and Combustible Gas Indicator (CGI) equipment was used to complete mobile and walking surveys in a multiple block radius. The surveys in the immediate vicinity of the explosion were completed by foot and included inspection of sewer system manholes for the presence of gas.

At 10:52 a.m. a two-inch medium-pressure plastic main on Glenwood Road was cut and capped and at 11:14 a.m. the two-inch medium-pressure steel main that supplied gas to 2945 South Wayne Road was cut and capped in the parking lot east of the building wall. After the mains were cut and capped, fire personnel continued to report the smell of gas in the air.

Between approximately 12:30 p.m. and 1:30 p.m., the source of the gas leak was discovered and actions were taken to mitigate the risk. A Consumers employee reported a gas read of 100% in a sanitary sewer manhole located in the alleyway behind 35018 Chestnut Street. Bar-hole testing conducted above the two-inch steel main near the sanitary sewer resulted in a 100% gas reading and gas was noted to be blowing out of the hole above the main. Consumers employees hand dug over the leak location and also removed the cover to the sanitary system in efforts to vent the gas to the atmosphere. Monitoring of sanitary sewer manholes was also initiated. The area was evacuated from Elizabeth Street to 4th Street and from Glenwood Road to Ash Street as shown in Figure 1 below.

Figure 1. Evacuation zone


of 27

Consumers employees conducted several bar-hole tests and free air reads in the vicinity of the leak. Gas was discovered inside the house at 35018 Chestnut Street at 7% lower-explosive-limit (LEL) and inside the garage at 35005 Chestnut Street at 24% LEL. Gas that had accumulated in these structures was migrating underground from the location of the main failure. Refer to Appendix A-2 for the Consumers Energy map detailing the bar-hole testing, leak survey, and positive gas readings found.

At approximately 1:50 p.m., Consumers employees attempted to squeeze the steel main approximately 40 feet east of the leak location. Multiple attempts were made to squeeze the main, but each attempt resulted in seam failures. At approximately 2:58 p.m., a plastic main segment was located and successfully squeezed near the intersection of Chestnut Street and Second Street. At approximately 3:05 p.m. an inspection at the location of the leak found no gas freely flowing. Refer to Appendix A-1 for the Consumers Energy Area Gas Map showing the locations and times that attempts were made to stop the flow of gas to the failed main.

At approximately 4:30 p.m. Consumers employees started excavation at the location of the leak and found a failed threaded coupling, approximately 233 feet east of the structure at 2945 South Wayne Road.

Summary of Return-to-Service

Leak surveys that were initiated immediately following the incident continued through December 30, 2010. Additionally, bar-hole testing at 35018 Chestnut Street was completed daily through January 7, 2011, with repeated positive results for presence of gas. The soil at this location was excavated and replaced with new fill in order to remove possibly contaminated soil. After new fill was placed, there were no further positive readings indicating presence of gas.

Consumers reports that as a result of the incident, service was interrupted to a total of 20 customers, including nine residential customers and 11 business customers. At approximately 7:45 p.m., Consumers started making repairs to return gas flow to a portion of the main in the alleyway and install temporary services that were necessary to return service to two houses with service taps downstream of the failure. Pressure testing was completed on the main and temporary services, and gas service was restored to all residential customers by approximately 1:30 a.m. on December 30, 2010, with relights completed by the end of that day. Figure 2 on the next page shows the restored main with the temporary service line taps.


of 27

Figure 2. Restored main with temporary service lines

After the fire department allowed residents to return to the area, they were offered an escort from Consumers, at which time a Consumers employee took free air readings prior to reentry by the residents. The free air readings were taken at strategic locations in the home such as near the furnace, water heater, and sanitary sewer. Consumers entered all homes on the north side of Chestnut Street between Wayne Road and Second Street on the north side of Chestnut Street.

Service lines to four business customers were removed due to building demolition. On January 7, 2011, new two-inch plastic main was installed on Chestnut Street to return service to one business and to provide permanent service to the two residential customers where temporary services lines were installed immediately following the incident. Six additional businesses were returned to service on April 13, 2012.

In efforts taken to prevent recurrence, Consumers Energy completed an investigation of the incident. Consumers did not identify any standards or procedures that required modification; however, current standards were restated and reinforced with employees through the Consumers Energy Compliance Advisory Bulletin for Gas Leak Survey and Gas Leak Investigation published on January 20, 2012. The Compliance Advisory Bulletin conveyed that employees performing leak survey must follow relevant standards, including recording encroachments to the pipeline during leak surveys and patrols, continuing investigation until leak is located and classified or otherwise identified as foreign gas or no leak found, and discussing findings with a field leader when no leak is found. Leak surveyors and first responders performing functions related to the Compliance Advisory Bulletin completed review of the document by March 12, 2012. A gas leak response procedure, proficiency, and competency review was completed by all gas service and distribution employees by October 31, 2012. Refer to Appendix D-4 for the Consumers Energy Compliance Advisory Bulletin.

Investigation Details

MPSC Staff conducted an investigation of the incident that included inspection and observation during emergency response, return to service, and post-incident testing and analysis; interviews


of 27

of employees and witnesses; review of records and procedures; and review of third-party and Company reports related to the incident.

At approximately 10:00 a.m. on December 29, 2010, Staff was telephonically notified by Consumers Energy of a building explosion at Wm. C. Franks Furniture Store located at 2945 South Wayne Road in Wayne, Michigan. Between approximately 12:00 p.m. and 2:00 p.m., multiple Staff immediately responded onsite to conduct inspection and investigation of the incident. Upon arrival, Staff made contact with the Consumers Field Leader on site and requested a briefing of the details currently known. Consumers also identified that employees were following the Company’s relevant standards. Staff was informed about the basic incident details including affected area, injured and missing persons, leak surveys that were in process at that time, and general information about the main and service line that serve 2945 South Wayne Road. Staff was also briefed about the two locations where main was cut and capped in efforts to eliminate the supply of gas to the building. A two-inch plastic medium-pressure main on Glenwood Road was cut and capped. A two-inch steel medium-pressure main in the alleyway accessed from Second Street between Glenwood Road and Chestnut Street that was cut and capped at a location underneath the parking lot located behind 2945 South Wayne Road. Gas odor was still present in the area and leak surveys continued to pinpoint the source. Staff was notified at approximately 12:30 p.m. that the leak surveys detected gas in a sewer system manhole located in the alleyway behind 35018 Chestnut Street. Bar-hole testing had identified the leak source to be the two-inch steel main near the sanitary sewer at a location approximately 233 feet away from the building wall at 2945 South Wayne Road. Figure 3 below shows a hole was hand-dug at the leak location and the sewer manhole cover was removed to allow gas to vent to the atmosphere.

Figure 3. Vented leak showing location of sewer manhole and fence

Since gas was suspected to be trapped in the sewer system, the area was evacuated at approximately 1:30 p.m. and Consumers continued leak survey and completed bar-hole testing


of 27

over an approximate six block radius. Several manhole covers were removed to allow any potentially trapped gas in the sewer system to vent into the atmosphere. Staff was onsite while Consumers attempted to stop the flow of gas to the leak by squeezing the steel pipe approximately 40 feet upstream of the leak near 35010 Chestnut Street, but the attempts were unsuccessful due to pipe splitting at the seam. Figure 4 below shows the steel main after the failed squeeze attempt and the fence located directly above it.

Figure 4. Failed attempt to squeeze steel main

Consumers then located a plastic segment of main near Second Street where a successful squeeze off was completed at approximately 2:58 p.m., as shown in Figure 5 below.

Figure 5. Successfully squeezed plastic main

After the flow of gas to the leak was eliminated, Consumers returned to the leak location in the alleyway behind 35018 Chestnut Street to confirm and investigate the failure. Excavation of the


of 27

site revealed that the two-inch steel main was separated at a threaded coupling. The fractured surfaces had a misalignment of approximately 2-1/2 inches. As shown in Figure 6 below, the west side of the fracture surface was displaced downward and to the north of the east side of the fracture. The gas main misalignment could indicate that the gas main was subject to external stresses while in service.

Figure 6. Two-inch gas main separation at coupling

The main was located at a depth approximately 38 inches below the ground surface. The steel main lie on the north side of the sewer manhole and was approximately three and a half inches away. The failure point was approximately 18 inches east of the sewer manhole. The failed section of main, cut approximately three feet on each side of the failure, was removed from the excavation and the exposed fracture surfaces were covered. Consumers took custody of the pipe sections to be stored in a secure location. Figure 7 below shows the fractured surfaces of the main sections removed from the excavation prior to being covered.

Figure 7. Fracture surfaces of failed main section


of 27

Throughout the course of the day on December 29, 2010, Staff was provided preliminary information related to the service line to 2945 South Wayne Road, the two-inch steel main where the failure occurred, and the sanitary sewer system. Staff also requested further information and documents related to the incident and system history including Consumers’ internal Incident Investigation Report, leak survey history, operating pressure charts, dispatch logs, service installation records, main or service repair records, cathodic protection records, maps of the area, and a list of Consumers’ employees that responded onsite and the respective duties performed. Staff remained onsite until approximately 8:00 p.m.

On December 30, 2010, Staff continued incident investigation beginning at a Consumers office location with a briefing about information gathered from the previous day’s events and also interviews of four Consumers’ employees including the Field Leader, the Service Workers who responded to the two leak calls prior to the explosion, and the Dispatch Supervisor. Refer to Appendix E for Staff notes related to the interviews. The Field Leader provided information related to the temporary repairs to restore service to the affected residential customers. Service would not be immediately restored to the commercial building structure. The Field Leader also provided Staff with further detail about timeline and activities from the previous day. The Field Leader indicated that there were five excavations and no frost in the ground was encountered at the failure point or near the house at 35018 Chestnut Street where bar-hole testing was completed. Of the five locations excavated, only one location had natural frost in the ground. A small amount of frost was encountered at the point where the steel main transitioned to plastic and when the main was excavated to be squeezed off. The frost encountered at this location was at a depth of approximately four inches below ground surface. The first leak call responder provided an account of the leak call response and the testing performed prior to leaving the site. The employee arrived onsite at 6:40 a.m. and left at 7:00 a.m. to respond to another leak call. The employee stated that he concluded the source of the gas was probably an inefficient furnace emitting unburned gas into the atmosphere. The employee also stated the type of equipment that was used for testing and that the equipment had been bump tested in the morning prior to the leak call and is calibrated every three months. The second leak call responder also provided an account of the leak call response and testing performed prior to the explosion. The employee arrived at 8:02 a.m. and indicated that he had a brief discussion with a fire department employee who was investigating gas odor complaints received by the fire department prior to beginning leak investigation. After receiving no positive readings for gas but occasionally observing the odor of gas, the employee contacted a supervisor to authorize dispatching a mobile leak detection unit. The employee was in the process of requesting mobile leak detection assistance when the explosion occurred at approximately 9:04 a.m. The Dispatch Supervisor confirmed times the leak calls were received, times employees were dispatched and arrived onsite, and the time that the first responding employee cleared the site.

Staff also reviewed the outside meter and manifold for 2945 South Wayne Road that was recovered from the incident site by Consumers. The meter was found with the plastic riser broken upstream of the lock wing and the fuel line broken downstream of the meter. The


of 27

regulator and meter did not show signs of fire exposure. It was concluded that the damage was due to the explosion. Figure 8 below shows the meter manifold during recovery at the incident site.

Figure 8. Meter manifold for 2945 South Wayne Road

Staff also returned to the incident site on December 30, 2010, and surveyed residential and commercial buildings damaged by the explosion. The sewer manhole, as shown in Figure 9 below, near the pipe failure was also preliminarily examined. The manhole had a concrete base with brick-and-mortar construction up to the precast manhole structure. As measured from the top of the manhole cover, the depth to the bottom of the sewer was 62 inches and the depth to the main was 38 inches. This manhole is identified as MH #6 on the Consumers Energy Bar-hole Testing and Leak Survey Map.

Figure 9. Sewer manhole MH#6


of 27

On January 3, 2011, Staff conducted onsite incident investigation with Consumers, City of Wayne Fire Department, and City of Wayne Department of Public Works. Investigation included reconstruction of the main relative to the sewer system and the chain-link fence in the alleyway behind 35018 Chestnut Street, inline camera inspection of the sewer system, and inspection of the drain system for 2945 South Wayne Road.

Chain-link fences were present in the abandoned alleyway behind Chestnut Street. Records related directly to the fence installed in the alleyway behind 35018 Chestnut Street could not be located; however, records for other chain-link fences indicate they were installed in 2008 and 2009. Reconstruction of the main and chain-link fence posts determined that the fence was installed directly above the main and multiple concrete footings for fence posts rested on the gas main. As shown in Figure 10 below, a footing was installed approximately three feet west of the failed coupling on the main.

Figure 10. Fence post above the two-inch gas main

The City of Wayne Department of Public Works used a televising camera to inspect sections of the sewer system in the area. The camera was used to inspect approximately 162 feet of sewer line between the manhole MH #7 and Chestnut Street and approximately 235 feet of sewer line between manhole MH #7 and manhole MH #6, which is the manhole located near the failed main.

Preliminary investigation was also completed with the assistance of the City of Wayne Fire Department to establish that a floor drain and sewer system trap located inside 2945 South Wayne Road were connected to manhole MH #7 by spraying water into the floor openings by observing the flow of water.

Other information discussed during the investigation on January 3, 2011, included an inspection of 2945 South Wayne Road conducted by Wayne Fire Department two weeks prior to the explosion; heating units for the building were roof mounted; two electric water heaters were located inside the building; and the City of Wayne Fire Department employee who was onsite during the incident as shift commander stated that gas could still be smelled continuously inside


of 27

the building after gas flow to the meter was stopped shortly after 11:00 a.m. Staff also had a discussion with a person related to the resident of 35018 Chestnut Street who indicated a sinkhole was discovered near manhole MH #6 approximately two years prior and the City of Wayne filled the sinkhole with dirt at that time. The person also indicated a second sinkhole was filled in the fall of 2010. Consumers followed up with the City of Wayne, but no records of sinkholes as described were located.

On January 6, 2011, Staff was onsite while Consumers performed leak tests on their facilities to rule out the possibility of leakage from the lines. Three main segments were pressure tested at 53 psig for 10 minutes and no leaks were identified as a result of the testing. The segments tested include the two-inch steel main from the failure point to the point where the main was cut and capped, located in the parking lot behind 2945 South Wayne Road, the two-inch steel main from the point where the main was cut and capped to the end of the main on Chestnut Street, which also included the service line to 2945 South Wayne Road and three other service lines, and the plastic main on Glenwood Road.

Staff requested excavation of the poured-concrete wall bordering the parking lot located east of 2945 South Wayne Road. The failed gas main passes under the wall and parking lot and continues through the abandoned alleyway to Second Street. Excavation revealed that the wall footing encased the two-inch steel main without a sleeve as shown below in Figure 11. The location of the failed threaded coupling was measured to be approximately 37 feet east of the wall.

Figure 11. Wall footing encasing two-inch steel main


of 27

Staff also spoke with the owner and an employee of the business located at 35059 Glenwood Road, which is in the same strip mall as 2945 South Wayne Road. The employee reported entering the building shortly before the explosion occurred. He indicated that he had turned on lights and adjusted the furnace, and then the explosion occurred after he turned on another light. The employee also stated that he did smell an odor when he entered the building, but indicated that he did not recall if it was indeed gas and that it may have also been from work completed the previous evening. He also stated that he did not smell gas in the air leading up to the day of the incident or when he first arrived just prior to the building explosion. The business owner stated that he had been in business at that location since 1974 and that the wall bordering the parking lot was built after that point. He estimated the wall had been constructed between 20 and 25 years ago.

On January 10, 2011, Staff returned onsite to observe further excavation of the main to determine if stresses existed on the gas main. A laser pointer was used to indicate the position of the main prior to excavation. The gas main was excavated on the west side of the wall approximately 15 feet to the end of the pipe. A deflection of approximately 4-¾ inches upward and approximately 6-½ inches to the south was observed after the overburden soil was removed and a prominent bend in the pipe was also observed. The gas main was then excavated on the east side of the wall to the failed coupling. It appeared to have a minimal bend slope downward away from the concrete wall toward the failure point. The pipe moved approximately one inch after it was completely excavated. A small amount of downward deflection was observed approximately six feet east of the wall. The pipe was cut on each side of the wall and a coring drill was used to remove the concrete and encased pipe as shown below in Figure 12. When the pipe was cut, it deflected approximately three eighths of an inch to the south and there was some movement on the section between the cut and failed failure point.

Figure 12. Concrete core encasing two-inch steel main

Staff was onsite from January 17 through January 20, 2011, during evidence collection. The gas fuel line for 2945 South Wayne Road was comprised of black steel piping and corrugated stainless steel tubing. An intact segment of fuel line on the north side of the building was pressure tested at ½ psi for 15 minutes and no leaks were detected. Staff later reviewed the


of 27

meter read history for 2945 South Wayne Road, which did not suggest a gas leak on the fuel line prior to the explosion. Refer to Appendix D-5 for the meter reading history.

Segments of the gas fuel line and furnaces were collected; however, the ability to assess if any open fuel lines existed prior to the explosion was significantly compromised during search and rescue efforts following the explosion. The materials that were recovered were damaged during the debris removal process, and it is also likely that not all material was recovered. Figure 13 below shows portions of gas fuel line recovered from the site.

Figure 13. Gas fuel line recovered from incident site

Investigation was also conducted while Staff was onsite from January 17 through January 20, 2011, to further establish communication between the drain system inside the building and the sewer system where gas was detected following the incident. The floor drains, sewer traps, manholes and other floor openings were marked as shown in Figure 14 below.

Figure 14. Aerial view of marked drains and sewer locations


of 27

Water was sprayed into floor drains and manholes to observe the flow of water. Upon doing so, it was concluded that water flowed from Floor Drains F and G into Sewer Trap E, as shown in Figure 15 below. The sewer lead for Sewer Trap E flows to Sanitary Sewer H. Sanitary Sewer H, which is identified as MH #7 on the map in Appendix A-2, is directly connected to Sanitary Sewer MH #6 located adjacent to the two-inch gas main in the alleyway behind 35018 Chestnut Street. The drain system for the building was later excavated and confirmed the flow paths determined. Sewer Crock E was found to have a non-watertight poured concrete base.

Figure 15. Building sewer system layout and flows

Staff also requested the City of Wayne Fire Department to perform a smoke test inside the sewer manhole MH #6 to determine where the gas could travel if it did enter into the sewer. A smoke bomb was placed inside sewer manhole MH #6 and the cover was placed over the manhole. Staff immediately witnessed the smoke permeating through the foundation walls of the manhole.


of 27

Staff also noted that the direction the smoke travelled was not consistent and thus determined that the possibility of a vacuum pulling the gas toward the building could not be ruled out.

On January 4, January 11, and January 12, Staff reviewed records associated with the incident at Consumers Energy’s Livonia Service Center. Staff was provided with a building schematic created by the City of Wayne Fire Department and an area map produced by Consumers. Staff reviewed records related to the two gas leak calls received and investigated prior to the explosion; Operator Qualification and Drug and Alcohol records for the two Consumers employees who responded to the leak calls; leak survey records; operating pressure history; cathodic protection; leak history; main repair history; and service line history. Additionally, Staff has reviewed additional documents and information related to the incident as requested or provided throughout the course of the investigation including maps, photographs, reports, and standards. Records related to the first leak call received on December 29, 2010, were reviewed. The records show that a leak call was received for 34924 Chestnut Street at 6:13 a.m. and indicated that there was a potentially hazardous condition, particularly outside in the backyard. A Consumers employee was dispatched and arrived onsite at 6:40 a.m. The employee completed the work order at 7:00 a.m. with comments indicating that no leaks were detected, but there was the odor of gas in air occasionally detected. Records related to the second leak call received on December 29, 2010, were reviewed. The records show that a leak call was received for 34650 Chestnut Street at 7:40 a.m. and indicated that there was gas odor detected outside in the backyard. A Consumers employee was dispatched and arrived onsite at 8:02 a.m. The employee had contacted a supervisor for approval for a mobile leak detection unit; however, the explosion occurred before the call to dispatch the unit was made. Review of the Operator Qualification records and Drug and Alcohol testing results for the two employees who responded to the leak calls the morning of the incident were reviewed and no issues were identified. In addition to the employees who responded to the two leak calls prior to the explosion, Staff reviewed the leak surveys completed following the explosion by additional employees responding to the incident. Leak surveys began immediately by the Consumers employee who was onsite at the time of the explosion. Other employees responded onsite to perform leak survey and detection in the area. Staff reviewed the records related to the leak surveys and spoke with employees for clarification. The affected area was surveyed using RMLD and CGI equipment. Staff reviewed Consumers Energy Gas Service Manual Standard 3-111 related to the Sensit Gold CGI equipment and the calibration of that equipment used in the leak surveys prior to and following the explosion. The standard states that the equipment is programmed to provide indication to the employee that calibration is due after three months, at which point the employee is responsible for scheduling calibration as soon as practical. Review of calibration records used indicated that four units exceeded three calendar months since the last equipment calibration.


of 27

The minimum exceedance was five days and the maximum exceedance was over three months. Refer to Appendix D-6 for Consumers Energy Standard 3-111 entitled Sensit Gold Instrument. Staff reviewed pressure charts for the affected main to determine if an overpressure had occurred. Seven-day pressure recordings were reviewed for three regulation stations upstream of the failure: Station 18, Michigan & Pershing; Station 62, Wayne & Melton; and Station 156, Woodbrook & Venoy. Station 62 was determined to be the station located closed to the failure and was operating at approximately 57 psig with no significant changes in operating pressure from December 28, 2010, through January 4, 2011. Pressure charts at Stations 18 and 156 also indicated no abnormal operating conditions. Staff also reviewed calibration records for each of the three pressure recording stations and found no issues. Refer to Appendix D-7 for the pressure recording charts for the three upstream regulation stations.

Staff reviewed records related to the construction of the two-inch steel main where the failure occurred. The records reviewed included 154 feet of two-inch steel main installed in 1940 and an additional 75 feet of two-inch steel main installed to extend the end-of-main to Chestnut Street in 1951. Staff noted that construction records for portions of the main in the alleyway were not able to be located. The records available for review were related to construction costs. No records were available related to the pipe specifications or the threaded couplings.

Staff reviewed service line records related to 2945 South Wayne Road. A service line was renewed with plastic service was installed in 2004 using a new tap on the two-inch steel main. Refer to Appendix D- 8 for the Service Work Order for 2945 South Wayne Road. Additionally, Staff also reviewed service line history for addresses on Glenwood Road, Wayne Road, and Chestnut Street. Staff reviewed records related to historical leak surveys for Wayne Road, Second Street, Glenwood Road, South Christine Street, and Chestnut Street. The last leak survey prior to the incident was completed on April 19, 2010, and no leaks were found. The records indicated that the leak survey was completed using mobile survey techniques in which a vehicle is utilized to find leaks on mains. Staff requested further information regarding the ability to complete the mobile survey for the main located in the abandoned alleyway between Chestnut Street and Glenwood Road since it was not accessible by vehicle. Staff interviewed the Consumers employee who completed the most recent survey and the employee indicated that walking surveys were completed on main in the alleyway using an RMLD; however, Consumers could not provide documentation supporting this.

Review of historical leak records indicated that main on Wayne Road required annual leak survey, main on Second Street and Glenwood Road required a five-year leak survey, and main on Christine required a three-year leak survey. The two-inch main in the alleyway between Chestnut Street and Glenwood Road was classified as cathodically unprotected pipe requiring a three-year leak survey. Records reviewed indicate that the leak surveys for these mains were completed as required.

Staff also reviewed records related to leak history, main repair, and cathodic protection for the affected main. Leak calls in recent history resulting in leaks found were related to customer fuel lines and appliances. There were no main repair records associated with the segment of main where the failure occurred. Staff reviewed two work orders from 1995 related to cathodic


of 27

protection of the affected main. A work order to install anodes and lead wires at 35018 Chestnut Street indicated that the work could not be completed due to the presence of fences and a concrete wall. A work order was successfully completed to install anodes and lead wire at 35080 Chestnut Street. The main segment later was moved to unprotected status in 1997. Review of historical leak survey records indicated that services from 2903 to 3007 Wayne Road, from 35059 to 35065 Glenwood Road, and from 35080 to 35084 Chestnut Street are located within business districts and are surveyed annually, and services from 34084 to 35018 Chestnut Street are located outside of a business districted and are surveyed on a five-year cycle. Staff reviewed records related to leak survey for 2945 South Wayne Road from 1992 through the most recent cycle and also records related to other services to find that the business district leak surveys were completed as required. Staff also reviewed records related to 34914 and 35018 Chestnut Street indicating that the services are cathodically unprotected steel service lines. Staff noted that leak survey records for these services showed that they were completed on a five-year cycle, which exceeds the requirements of Michigan Gas Safety Standards Rule 192.723. Refer to Appendix D-9 for the service leak survey records reviewed for addresses located on Chestnut Street. Staff reviewed records related to odorization of the gas supplied to the affected area. Gas was supplied to the area by two odorizers, referred to as Northville and Newburgh. Staff reviewed the Odorant Injection Report and Weekly Odorant Check Requirements Report. Staff also reviewed records from the odorizer intensity test point, which is after gas from the two odorizers is blended, located at 36850 Van Born. Staff also reviewed maintenance and repair history for the odorizers for the year prior to the incident. Annual maintenance was performed as required and no repairs were necessary. Staff also reviewed Consumers Gas Distribution Manual Standard 5-8 entitled Fire/Explosion Investigation, which requires an odorant sniff test after an explosion by the first employee to arrive at the scene. Furthermore, the Standard 5-8 states the Gas Field Leader is responsible for “determining the extent and source of the gas leakage,” and steps taken by Field Workers under the direction of the Field Leader include odorant sniff testing and documenting the results and location of the tests. The odorant check or sniff test requires the employee to determine if gas odor is perceptible during a 10-second gas release. A Consumers employee may also request a public safety person to determine if gas odor is perceptible. Although Consumers employees and fire department personnel indicated that the gas odor was perceptible during the emergency response when gas was blowing, Staff was not provided with records documenting odorant sniff tests. Refer to Appendix D-10 for Consumers Energy Standard 5-8.

Staff reviewed staking requests for the affected area. One staking request of particular interest was located for 2945 South Wayne Road from October 2004, identified as MISS DIG ticket #A42950700. The work type was identified as landscaping and the staking request was for the entire lot for Frank’s Furniture. No details were available regarding the actual landscaping work completed. Staff also reviewed staking requests for the affected area near Wayne Road Glenwood Road for the 30-day period preceding the incident. Three requests were located, but they were determined to not be relevant to the incident investigation.


of 27

The sections of two-inch steel main removed after the incident occurred were transferred to Stork Climax Research (Stork) for laboratory testing on May 11 and 12, 2011, which included visual examination and photographing of samples, tensile testing, hardness testing, metallurgical examination, radiographic examination, scanning electronic microscopic examination, physical measurements of the pipe, and collection of soil samples from the pipe. Refer to Appendix F-1 for the Consumers Energy report entitled Review of Testing Completed by Stork Climax Research. Collection of soil samples from the incident site for chemical analysis was planned for August 2011; however, the collection of samples was cancelled. The Consumers Energy Incident Investigation Report dated December 15, 2011, discussed the results of the laboratory testing completed by Stork. Refer to Appendix G for the Consumers Energy Incident Investigation Report. The Consumers report Metallurgical Examination Findings concluded as follows:

Separation at the threaded pipe connection was due to a material overload condition. The application of an undetermined downward force on the top portion of the pipe near the 12:00 position resulted in crack initiation near the 5:30 position of the pipe. The cracking initiated in the pipe threaded area at the pipe/coupling interface of the 2-inch gas main. After crack initiation, rapid crack propagation occurred simultaneously in the clockwise and counterclockwise directions around the circumference of the pipe until complete separation of the pipe occurred. No pre-existing defect was detected at the suspected point of origin. The 6:00 position of the West Side pipe section contained the thinnest wall thickness in the threaded connection. The majority of the fracture surface exhibited a predominantly brittle-like morphology (transgranular cleavage) consistent with that expected of a rapid crack growth evolution. Ductile fracture surface features were observed at the 8:30 to 12:30 position indicating final failure occurred in this region. The separated pipe section maintained a predominantly ferritic microstructure which is as expected of pipe material of this vintage. A longitudinal seam weld was located at the 3:00 position of the West Side Pipe as installed. The longitudinal seam weld was not contributory to the separation. The composition of the separated pipe section met the chemical requirements of API 5L (1940 edition). The mechanical properties of the separated pipe section met the requirements of API 5L (1940 edition).


of 27

Based on the visual examination of the pipe, Consumers concluded that there was no evidence of localized pitting damage to the outer diameter surfaces, the fracture surfaces on both the east and west sides of the failure point showed no evidence of abnormal ovality, and the longitudinal seam weld was intact and not contributory to the failure. Based on the radiographic evaluation of the fracture surfaces, Consumers concluded that there were no indications of any abnormal conditions that contributed to the failure. Based on the Scanning Electron Microscope examination, Consumers concluded that there was no indication of preexisting defects that acted as stress risers. In a March 21, 2012 letter, Staff responded to the Consumers incident report requesting clarification on eight items, which included identifying, the process used to manufacture the pipe, clarifying certain dimensions referenced in the report, and a calculation of the load required to cause the pipe to fail and the calculated stress acting on the pipeline prior to failure. In response to Staff’s request, Consumers provided Staff with responses to requests for clarification, which is attached as Appendix F-2, and the April 19, 2012 letter from Exponent Engineering to Consumers, which is attached as Appendix F-3 and concluded:

In summary, approximately 1,250 pounds of force at the sewer manhole access will yield the coupling’s threads with a displacement of 2 inches – assuming the modulus of the foundation is approximately 4 psi. The modulus of the foundation will change as the soil trench compaction varies. If the modulus of foundation is increased, the load to yield and displace the coupling’s threads will increase too. The actual modulus of the foundation is unknown at this time.

Additionally, Staff requested metallography on a transverse section of the threads on the failed end of the fracture surface to determine if, and to what extent, cracking was evident in the adjacent threads. The subsequent examination performed at Consumers Energy Laboratory Services on May 9, 2012, and concluded that it “did not reveal any cracking in the threads adjacent to the fracture in the west side fracture surface sample that would have contributed to the failure of the gas pipe.” Refer to Appendix F-4 for the review of additional metallurgical examination completed by Consumers. In a June 18, 2012 letter to Consumers, Staff requested that the collection of soil samples be completed to determine actual soil stiffness. Staff further requested that the soil testing make attempts to corroborate the claims of a sinkhole near the failure location and to determine if the parking lot or concrete wall had settled since construction and contributed to the pipeline failure. Staff requested that the actual soil stiffness values as well as the data from the additional metallography testing on May 9, 2012, be used to recalculate the load required to cause the pipe to fail at the threaded joint. Staff also requested the documentation of the analysis of explosion-related pressure waves. In response to Staff’s request, Consumers provided Staff with the July 5, 2012 letter from Exponent Engineering to Consumers containing their findings related of the pressure necessary to damage the poured-concrete wall and the pressure necessary to cause the damage to structures


of 27

as observed following the explosion. Exponent concluded the minimum pressure necessary to cause the masonry wall to overturn to the east was calculated to be 0.36 psi to 0.52 psi. The data collected indicates the wall did not display any movement or tilting in the east-west direction as a result of the explosion. Exponent documented all structural damage, or lack thereof in the surrounding areas as a result of the explosion. Many damage indicators in close proximity to the masonry wall displayed damage consistent with being exposed to an over pressure of approximately 0.15 psi or less. Refer to Appendix F-5 for the analysis of the pressure wave completed by Exponent. Soil testing was completed on September 17, 2012, and Staff was onsite to observe. The November 6, 2012 report completed by Exponent Engineering, which is in Appendix F-6, concluded:

1. The topographical survey of the parking lot revealed that no clear general trends exist as to the locations and characteristics of the crack patterns other than slightly higher concentrations of cracks in areas subjected to higher traffic. Thus, it appears to have been no differential settlement of the parking lot over the distribution line that could have contributed to the applied load on the pipe at the time of the rupture.

2. The topographical survey of the privacy wall revealed a slight dip in the top of the wall elevation (approximately 0.6 inches) in the vicinity of where the gas pipe was located. Other sections of the privacy wall included in the survey also demonstrated a slightly lower difference in the top of the wall elevations. Thus, there appears to have been no significant settlement of the privacy wall that could have contributed to the applied load on the pipe at the time of rupture.

3. Soil sampling revealed that the soil conditions in the vicinity of the failed pipe were brown fine sand with varying amounts of silt.

4. Laboratory testing of soil samples collected from the site indicate that the soil conditions east of the privacy wall (in the area of the failure location) were very similar and consistent in all of the locations analyzed. This indicates that there is no evidence of a sink hole being present in the right-of-way at any time prior to the rupture.

5. Based on laboratory testing of the soil sample closest to the pipe failure location, the soil stiffness when exposed to a load greater than 800 pounds would be 29.2 psi.

6. Based on measurements of the root of the thread where the fractured initiated a notch stress concentration factor of 4.57 was calculated.

7. Using the measured soil stiffness of 29.2 psi and the measured notch stress concentration factor of 4.57, an elastic beam foundation model predicts that at least 1,200 pounds of force is required at the sewer manhole access to yield and fracture the threads of the coupling 18 inches away. This is very close to the originally calculated load of 1,250 lbs., which was calculated using the following estimated values for these factors: soil stiffness of 4 psi and a notch stress concentration of 1.64. The small difference in the calculated load using the estimated values and the calculated load using the measured values


of 27

because the effect of the increased soil stiffness, which increases the required load to break the pipe, is balanced out by the effect of the increased notch stress concentration factor, which decreases the required load.

In a telephone conference with Exponent and Consumers on December 19, 2012, Staff requested clarification regarding Exponent’s calculations and analyses in the report. Exponent indicated that the calculated load of 1,200 pounds includes the sum of all component loads including frost heave, soil loading, sewer manhole, fence post footings, concrete wall, and potential bending of the main during construction. Exponent indicated that a deflection of 0.3852 inches at the point of failure was used in the calculation rather than the misalignment of approximately 2-1/2 inches when the failure was discovered. Exponent explained the additional misalignment could be attributed to the excavation activities during the repairs. The gas main may have still been under some lateral stresses that could have caused the main to be displaced after the overburden soil was removed. The measured misalignment would estimate a load significantly higher than the 1,200 pounds and that the main could not have sustained such a load. Also, Exponent stated that the force of the explosion was not considered a contributing factor to the main failure. The pressure wave associated with explosion travelled laterally away from the building lengthwise along the main; however, the analysis suggested that a transverse load was applied to cause failure so it is not reasonable to assume the failure at the coupling was a result of the explosion. Regarding the soil samples to determine if a sinkhole existed near the coupling failure, Exponent discussed that soil samples were taken from areas where the ground was not disturbed from the excavation activities during the excavation and repair of the main. Staff expressed concern that those locations were not a relevant sample of the area where the sinkhole was suspected and concluded that soil testing could not rule out the existence of a sinkhole due to the disturbance of the soils during main excavation and repair.

Findings and Contributing Factors

As a result of the investigation conducted, Staff concluded that the apparent cause of the failure that resulted in the explosion at 2945 South Wayne Road on December 29, 2010, was outside force damage to the two-inch steel main located in the alleyway behind 35018 Chestnut Street. Staff considered and is in agreement with the December 15, 2011 Consumers Energy Incident Investigation Report that states that the separation at the threaded coupling was the result of a material overload condition caused by forces applied to pipe. Staff identified the following four contributing factors that led to the failure of the affected gas main:

Contributing Factor 1: The City of Wayne installed a sanitary sewer system after the construction of the affected gas main. An eight-inch sewer line runs parallel to the two-inch steel main. The gas main was located less than four inches north of sewer manhole MH #6 and the failed coupling was located approximately 18 inches east of the sewer manhole MH #6. Because of the close vicinity, construction of the sewer most likely exposed the gas main. The construction of the sanitary sewer or settlement near the sewer manhole contributed to the external forces applied to the gas main.


of 27

Contributing Factor 2: A residential chain-link fence was installed after the construction of the affected gas main. It was located directly on top of the gas main in the abandoned alleyway behind 35018 Chestnut Street. The concrete footings for the fence posts were resting on the gas main in multiple locations and exerted downward forces on the main. Construction of the fence may have exposed the gas main at the post locations.

Contributing Factor 3: The City of Wayne constructed a poured concrete wall at the edge of the parking lot behind 2945 South Wayne Road after the construction of the affected gas main. The failed coupling was located approximately 37 feet east of the poured concrete wall. Excavation discovered that the wall footing wall encased the gas main. Movement of the gas main was observed when the overburden soil was removed from the gas main near the wall. The construction or settlement of the wall may have contributed to the external forces on the gas main. No sleeve or conduit was used where the wall footing was poured around the gas main, causing the concrete footing to prevent free movement of the pipe in the soil during the freeze and thaw cycle. Settlement of the nearby soils may also have contributed to the external forces on the gas main.

Contributing Factor 4: A sinkhole was reported in the vicinity of the failure that was filled with soil by the City of Wayne. Although claims of the sinkhole could not be corroborated, it is possible that a sinkhole may have been caused by infiltration through the permeable brick-and-mortar construction of the sewer manhole. The settlement of the soil in this location may have contributed to the external stresses on the gas main.

Staff does not consider the pressure wave from the explosion as a contributing factor to the failure of the affected gas main. The analysis of the failure by Consumers concluded that the failure was caused by downward forces applied to the top of the pipe and the pressure wave would not exert such forces on the pipe. While Staff agrees the Consumers Energy Incident Investigation Report where it states that the possibly that an inside leak may have existed inside the building could not be ruled out because inspection of the fuel line and equipment could not be completed, Staff determined that it was unlikely that an inside leak caused the explosion. In reaching this determination, Staff considered that the historical gas usage and last meter reading did not indicate abnormally high usage, the post-explosion review of the meter and manifold did not identify any discrepancies, the furnaces were located on the top of the building and therefore a leak at a furnace would vent to the atmosphere, the Fire Department did not indicate any issues from the inspection performed approximately two weeks prior to the incident, and gas odor was not detectable in the alleyway behind the building despite the odor being detected by the Consumers employee at points further east from the building.

Staff concluded that after the gas main failure occurred, gas blowing from the leak migrated through the sewer system into 2945 South Wayne Road. Staff identified the following two contributing factors that led to the explosion that occurred after the failure of the affected gas main:


of 27

Contributing Factor 1: The coupling failed at a location less than four inches north and eighteen inches east of the sanitary sewer manhole. The porous construction of the manhole provided the path of least resistance for the gas and allowed gas to migrate through the sewer system into 2945 South Wayne Road. The presence of gas in the sanitary sewer and other nearby structures was confirmed after the explosion. Investigation following the incident also confirmed that there was communication between the sanitary sewer system and a sewer trap connected to various floor drains within 2945 South Wayne Road. The sewer trap was found to be non-water tight, which provided a path for the gas to escape into the building.

Contributing Factor 2: The Company received two leak calls in the vicinity prior to the explosion. The first employee arrived at 6:40 a.m. and could not locate a leak. The employee conducted free air readings inside the reporting address, outside of the reporting address and neighboring structures, and in a nearby sewer manhole. A bar-hole test was completed over the service riser at the reporting address; however, a bar-hole test was not completed over the gas main. The employee documented that an occasional gas odor was detected in the atmosphere, but no gas leak was found. The employee did not discuss findings with a field leader prior to completing leak investigation and leaving the site at 7:00 a.m. The employee later stated to Staff that the assumption was made that the source of the gas was an inefficient furnace emitting unburned gas into the atmosphere. A complete and thorough investigation in accordance with Consumers Standard 5-2, Gas Leak Investigation and Response, that included bar-hole testing over the main and discussing findings with a field leader, immediate actions may have been taken to identify the source and extent of the leak and evacuate the area until conditions were made safe.

Consumers Energy Company Wayne Pipeline Failure and Explosion

Documents

Transcript of Consumers Energy Company Wayne Pipeline Failure and Explosion